Road Drainage and Water Environment

Introduction

This chapter presents the Stage 1 Road Drainage and the Water Environment (RDWE) assessment for the A75 Springholm and Crocketford Improvements (hereafter referred to as “the proposed scheme”). The assessment has been undertaken in accordance with the Design Manual for Roads and Bridges (DMRB) Design Manual for Roads and Bridges (DMRB) LA 113 - Road drainage and the water environment (revision 1) (hereafter referred to as “DMRB LA 113”) and other relevant guidance set out in this chapter. Where elements of the assessment methods outlined within DMRB LA 113 cannot be followed, this is detailed in the Assumptions and Limitations section of this chapter.

Legislative and Policy Framework

This section provides a summary of the legislation and polices relevant to the RDWE assessment.

Legislation

The following legislation is relevant to this RDWE assessment:

The Water Environment and Water Services (Scotland) Act 2003 (WEWS)

These regulations cover rivers, lochs, transitional waters (estuaries), coastal waters groundwater and groundwater dependent wetlands.

Flood Risk Management (Scotland) Act 2009

An Act of the Scottish Parliament to make provision about the assessment and sustainable management of flood risks.

Climate Change (Scotland) Act 2009

This Act of the Scottish Parliament creates the statutory framework for greenhouse gas emissions reductions in Scotland.

The Water Environment (Controlled Activities) (Scotland) Regulations 2011

This Act of the Scottish Parliament creates the statutory framework for greenhouse gas emissions reductions in Scotland.

Regulations to control engineering works within inland surface waters, as well as point source discharges, abstractions and impoundments. Regulations define levels of authorisation which require approval from the Scottish Environment Protection Agency (SEPA).

The Pollution Prevention and Control (Scotland) Regulations 2012

The Pollution Prevention and Control (Scotland) Regulations 2012 establish a system to control pollution from installations or mobile plants carrying out specified activities in Scotland.

The Designation of Nitrate Vulnerable Zones (Scotland) Amendment Regulations 2015

EU Directive 1991/676/EEC on protecting waters against pollution caused by nitrates from agricultural sources requires member states to review and, if necessary, revise action programmes for designated nitrate vulnerable zones.

The Water Environment (River Basin Management Planning etc.) (Miscellaneous Amendments) (Scotland) Regulations 2015

Amends the river basin management planning regulations and the Water Environment Controlled Activities (Scotland) Regulations 2011 to take account of Directive 2013/39/EU, 2014/80/EU relating to water quality standards and priority substances.

The Water Environment (Water Framework Directive (WFD)) (Northumbria and Solway Tweed River Basin Districts) (Amendment) Regulations 2016

The Northumbria Regulations and Solway Tweed Regulations transposed the WFD for river basin districts that are partly in England and partly in Scotland.

Water Environment (Miscellaneous) (Scotland) Regulations 2017

These regulations amended the Water Environment (Controlled Activities) (Scotland) Regulations 2011. The regulations have been revised to provide greater control over activities which may affect Scotland’s water environment, whilst also encouraging improvements in construction practice.

Water Environment (Controlled Activities) (Scotland) Amendment Regulations 2021

These regulations make changes to Scottish legislation, as a result of the European Union (EU) Exit, relating to the water environment and flood risk management.

National Policy

The following national policy documents are considered in this assessment:

• National Planning Framework 4 :
  • Policy 22 Flood risk and water management – The intent is to strengthen resilience to flood risk by promoting avoidance as a first principle and reducing the vulnerability of existing and future development to flooding.

Local Policy and Plans

The following local policies and plans are considered in this assessment:

• River Basin Management Plan for Scotland 2021-2027 .
• Dumfries and Galloway Council Local Development Plan 2 :
  • NE11: Supporting the Water Environment
  • NE12: Supporting the Water Environment
  • IN7: Flooding and Development
  • IN8: Surface Water Drainage and Sustainable Drainage Systems (SuDS)
• Flood Risk Management Plan, Solway Local District Plan

Assessment Methodology

Overview

The RDWE assessment includes the following elements:

• Surface water quality: the importance and potential impacts on surface water quality as a result of the proposed scheme.
• Surface water supply: the importance and potential impacts on the quantity of surface water-fed water supplies as a result of the proposed scheme.
• Hydromorphology: the potential for impacts from the proposed scheme upon fluvial landforms associated with river systems, and the flow and sediment transport processes which create and sustain them.
• Flood risk: potential risk of flooding from all sources to the proposed scheme or elsewhere as a result of the proposed scheme.

Data Sources

The baseline conditions have been assessed using a desktop review. The data sources used to establish the baseline conditions are outlined in the list below:

• Aerial imagery
• Ordnance Survey Mapping (OS Mapping) (OS 1:25,000 to 1:50,000 scale mapping)
• Water Classification Hub
• SEPA Flood Maps (including future climate change flood maps)
• National Flood Risk Assessment Data Explorer Tool (flood risk and historical flood events information)
• Flood Risk Management Strategies: Solway Local Plan District (Springholm Potentially Vulnerable Area 14/10)
• National River Flow Archive (NRFA) (river gauging information)
• Scotland’s Environment Web (Environmental information)
• Newspaper Articles:
  • Heavy rainfall causes road chaos across Dumfries and Galloway
  • Storm Frank brings flooding and New Year chaos to the Stewarty
  • Stewartry roads disappear under floodwater after wind and rain batter Dumfries and Galloway

Assessment of Impacts and Effects

The identification of potentially significant effects on RDWE have been derived from a qualitative desktop review. The assessment accounts for the potential impacts across the river catchments as well as groundwater and surface water receptors. The assessment also accounts for relevant aspects of other environmental factors such as geology, soils and biodiversity. A full assessment of effects are discussed in the Biodiversity Chapter and Geology, Soils and Groundwater Chapter of this EAR.

Importance Criteria

Where possible, the receptors are assigned an importance based on the sub-sections below which is a development of the typical examples outlined in Table 3.70 of DMRB LA 113. The importance of a potential receptor is typically considered in terms of indicators such as quality, scale, rarity and substitutability and categorised on a scale of low to very high using various sources of information. Surface water supply is assessed ‘Very High’ or ‘High’ importance only in relation to the number of properties/receptors a water resource is supplying. To note, Q95 (the 5 ^th percentile flow) presents the flow in cubic metres per second which was equalled or exceeded for 95% of the flow record. The Q95 flow is a significant low flow parameter particularly relevant in the assessment of river water quality consent conditions.

DMRB LA 113 - Nationally Significant Attribute of Very High Importance Criteria

Typical examples from DMRB LA 113 for nationally significant attribute of very high importance criteria are listed below:

• Surface Water: Watercourse having a WFD classification shown in a River Basin Management Plan (RBMP)and Q ₉₅ ¹ greater than or equal to 1.0m³/s.
• Site: protected/designated under European Commission (EC) or UK legislation (Special Area of Conservation (SAC), Special Protection Area (SPA), Site of Special Scientific Interest (SSSI), Ramsar site, salmonid water)/species protected by EC legislation.
• Flood Risk: Essential infrastructure or highly vulnerable development.

The applicable scheme examples relevant for nationally significant attribute of very high importance criteria are listed below:

Surface Water Quality

WFD classified water body achieving ‘High’ Physico-chemical and Biological elements status, ‘Pass’ for Specific pollutants and /or Priority substances.

Q ₉₅ likely to be greater than or equal to 1.0m³/s.

Watercourse part of a site protected/designated under International/EC/EU or UK legislation (SAC, SPA, SSSI, Ramsar site). Non WFD classified watercourses may be applicable if part of a protected site.

Surface Water Supply

Water resource extensively exploited for public, private domestic and/or agricultural and/or industrial use, feeding ten or more properties.

Hydromorphology

WFD classified water body achieving ‘High’ Morphology status. WFD classified water body considered to be sensitive to additional morphological pressures as it is within 2.5% of a morphological condition limit boundary (for example High/Good, Good/Moderate, Moderate/Poor).

Non WFD classified watercourses may be applicable if they demonstrate qualities such as: a channel in stable equilibrium and exhibiting a range of natural morphological features (such as pools, riffles and bars); diversity in morphological processes reflects unconstrained natural function; free from artificial modification or anthropogenic influence.

Flood Risk

Most Vulnerable Land Uses, including essential infrastructure as defined in Flood Risk and Land Use Vulnerability Guidance (hereafter referred to as “LUPS-GU24”) at risk from flooding during the 0.5% Annual Exceedance Probability (AEP) (200-year) plus climate change (CC) event.

DMRB LA 113 Nationally Significant Attribute of High Importance Criteria

Typical examples from DMRB LA 113 for nationally significant attribute of high importance criteria are listed below:

• Surface Water: Watercourse having a WFD classification shown in an RBMP and Q ₉₅ less than1.0m³/s.
• Flood Risk: More vulnerable development.

The applicable scheme examples relevant for nationally significant attribute of high importance criteria are listed below:

Surface Water Quality

WFD classified water body achieving or having established RBMP objectives (for a later RBMP cycle) to achieve ‘Good’ Physico-chemical and Biological elements status (‘Good potential’ for Heavily Modified Water Bodies (HMWBs)), ‘Pass’ for Specific pollutants and /or Priority substances.

Q95 likely to be less than1.0m³/s.

Contains species protected under EC or UK legislation Ecology and Nature Conservation but is not part of a protected site. Non WFD classified water bodies may be applicable if protected species are present, indicating good water quality and supporting habitat.

Surface Water Supply

Valuable water supply resource due to exploitation for public, private domestic and/or agricultural and/or industrial use, feeding fewer than ten properties.

Hydromorphology

WFD classified water body achieving or having established RBMP objectives (for a later RBMP cycle) to achieve ‘Good’ Morphology status.

Non WFD classified watercourses may be applicable if they demonstrate qualities such as: a channel achieving near-stable equilibrium and exhibiting a range of natural morphological features (such as pools, riffles and bars); diversity in morphological processes reflects relatively unconstrained natural function, with minor artificial modification or anthropogenic influence.

Flood Risk

Highly Vulnerable Land Uses as defined in LUPS-GU24 at risk from flooding during the 0.5% AEP (200-year) plus CC event.

DMRB LA 113 Nationally Significant Attribute of Medium Importance Criteria

Typical examples from DMRB LA 113 for nationally significant attribute of medium importance criteria are listed below:

• Surface Water: Watercourses not having a WFD classification shown in an RBMP and Q ₉₅ greater than 0.001m³/s.
• Flood Risk: Less vulnerable development.

The applicable scheme examples relevant for nationally significant attribute of medium importance criteria are listed below:

Surface Water Quality

Water body not classified under WFD. May have a number of anthropogenic pressures and/or pollutant inputs from discharges (licenced under Controlled Activities Regulations (CAR)) and/or surrounding land-use relative to flow volume. Q ₉₅ likely to be greater than 0.001m³/s.

Hydromorphology

Water body not classified under WFD. A channel currently showing signs of historical or existing modification and artificial constraints. Attempting to recover to a natural equilibrium and exhibiting a limited range of natural morphological features (such as pools, riffles and bars).

Flood Risk

Least Vulnerable Land Uses as defined in LUPS-GU24 at risk from flooding during the 0.5% AEP (200-year) plus CC event.

DMRB LA 113 Nationally Significant Attribute of Low Importance Criteria

Typical examples from DMRB LA 113 for nationally significant attribute of low importance criteria are listed below:

• Surface Water: Water body not having a WFD classification shown in a RBMP and Q ₉₅ less than or equal to 0.001m³/s.
• Flood Risk: Water compatible development.

The applicable scheme examples relevant for nationally significant attribute of low importance criteria are listed below:

Surface Water Quality

Water body not having a WFD classification shown in a RBMP. May have a large number of anthropogenic pressures and/or pollutant inputs from discharges (licenced under CAR) and/or surrounding land-use relative to flow volume. Q ₉₅ likely to be less than or equal to 0.001m³/s.

Hydromorphology

Water body not classified under WFD. A channel currently showing signs of extensive historical or existing modification and artificial constraints. There is no evidence of diverse fluvial processes and morphology and active recovery to a natural equilibrium.

Flood Risk

Water Compatible Land Uses as defined in LUPS-GU24 at risk from flooding during the 0.5% AEP (200-year) plus CC event.

Magnitude

Impacts are typically assigned a magnitude through a high-level assessment based upon the following sub-sections below which is a development of the typical examples outlined in Table 3.71 of DMRB LA 113. The assessment is based on the degree of direct and indirect impact and whether the impact would be temporary or permanent. The magnitude of impact is then categorised on a scale of ‘Major’ to ‘Negligible’ for both adverse and beneficial impacts.

However, due to the limited design information available at this stage, it has not been possible to assign a specific magnitude of impact to each receptor potentially impacted by each of the improvement strategies. The following sub-sections have therefore been used only as a guide to determine where likely significant effects may occur. A more detailed assessment of magnitude following the approach outlined below will be carried out as proposed scheme design information becomes available at DMRB Stage 2.

DMRB LA 113 Magnitude Criteria and Examples – Major Adverse Magnitude

DMRB LA 113 Criteria for Major Adverse Magnitude is listed below:

• Results in loss of attribute and/or quality and integrity of the attribute.

The applicable scheme examples relevant for the Major Adverse Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

Construction works in-channel and/or extensive construction works adjacent to a watercourse which are therefore likely to risk a major, measurable shift from baseline water quality. Risk of adverse impacts on protected aquatic species. Construction works on multiple tributaries of a watercourse resulting in the risk of a significant cumulative impacts on water quality.

Loss or extensive change to a designated nature conservation site.

Failure of both acute-soluble and chronic-sediment related pollutants in HEWRAT and compliance failure with EQS values. Calculated risk of pollution from a spillage greater than or equal to 2% annually (spillage assessment).

For WFD classified water bodies, water quality impacts have the potential to cause deterioration in WFD status.

Surface Water Supply

Long term loss or change to water supply.

Hydromorphology

Loss of, or extensive adverse changes to the watercourse bed, banks and vegetated riparian corridor resulting in changes to existing morphological features and/or channel planform and cross section and/or natural fluvial processes. Impacts would be at the water body scale.

For WFD classified water bodies, impacts have the potential to cause deterioration on morphology status or prevent the achievement of ‘Good’ Morphology status due to an increase in the extent of morphological pressures on the water body.

Flood Risk

Increase in peak flood water level for the 0.5% AEP (200-year) plus CC event of greater than or equal to 100mm.

DMRB LA 113 Magnitude Criteria and Examples – Moderate Adverse Magnitude

DMRB LA 113 Criteria for Moderate Adverse Magnitude is listed below:

• Results in effect on integrity of attribute, or loss of part of attribute..

The applicable scheme examples relevant for the Moderate Adverse Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

Construction works adjacent to a watercourse which are therefore likely to risk a moderate, measurable shift away from baseline water quality.

Failure of both acute-soluble and chronic-sediment related pollutants in Highways England Water Risk Assessment Tool (HEWRAT) but compliance with Environmental Quality Standards (EQS) values. Calculated risk of pollution from spillages greater than or equal to 1% annually and less than 2% annually.

Partial loss in productivity of a fishery.

For WFD classified water bodies, water quality impacts may contribute to, but not cause a reduction in water body WFD classification.

Surface Water Supply

Temporary disruption or deterioration in a water supply.

Hydromorphology

Adverse changes to on the water feature bed, banks and vegetated riparian corridor resulting in changes to existing morphological features and/or channel planform and cross section and/or natural fluvial processes. Impacts would be at the reach scale.

For WFD classified water bodies, impacts may increase the extent of morphological pressures. May contribute to, but not cause a deterioration of Morphology status.

Flood Risk

Increase in peak flood water level for the 0.5% AEP (200-year) plus CC design flood event of greater than or equal to 50mm and less than 100mm.

DMRB LA 113 Magnitude Criteria and Examples – Minor Adverse Magnitude

DMRB LA 113 Criteria for Minor Adverse Magnitude is listed below:

• Results in some measurable change in attributes, quality or vulnerability.

The applicable scheme examples relevant for the Minor Adverse Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

Construction works within the watercourse catchment that may result in a risk of a minor, measurable shift from baseline water quality.

Failure of either acute soluble or chronic sediment related pollutants in HEWRAT.

Calculated risk of pollution from spillages greater than or equal to 0.5% annually and less than 1% annually.

Hydromorphology

Slight adverse changes to/impacts on the water feature bed, banks and vegetated riparian corridor resulting in changes to existing morphological features and/or channel planform and cross section and/or natural fluvial processes. Impacts would be at the local scale.

For WFD classified water bodies, impacts may result in a slight increase the extent of morphological pressures or occur where there are existing morphological pressures. Morphology status unaffected.

Flood Risk

Increase in peak flood water level for the 0.5% AEP (200-year) plus CC design flood event of greater than or equal to 10mm and less than 50mm.

DMRB LA 113 Magnitude Criteria and Examples – Negligible Magnitude

DMRB LA 113 Criteria for Negligible Magnitude is listed below:

• Results in effect on attribute, but of insufficient magnitude to affect the use or integrity.

The applicable scheme examples relevant for the Negligible Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

Construction works within the watercourse catchment that are not anticipated to result in a risk of a change in water quality.

No risk identified by HEWRAT (pass both acute-soluble and chronic-sediment related pollutants).

Risk of pollution from spillages less than 0.5%.

Hydromorphology

Minimal or no measurable change from baseline conditions in terms of sediment transport, channel morphology and natural fluvial processes. Any impacts are likely to be highly localised.

Flood Risk

Negligible change in peak flood water level for the 0.5% AEP (200-year) plus CC design flood event of up to less than plus or minus 10mm.

DMRB LA 113 Magnitude Criteria and Examples – Minor Beneficial Magnitude

DMRB LA 113 Criteria for Minor Beneficial Magnitude is listed below:

• Results in some beneficial effect on attribute or a reduced risk of negative effect occurring.

The applicable scheme examples relevant for the Minor Beneficial Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

HEWRAT assessment of either acute soluble or chronic-sediment related pollutants becomes pass from an existing site where the baseline was a fail condition. Calculated reduction in existing spillage risk by 50% or more (when existing spillage risk is less than 1% annually).

Hydromorphology

Potential for slight improvements to channel morphology. For WFD classified water bodies, impacts may result in a slight decrease in the extent of morphological pressures but insufficient in extent to improve water body WFD morphology classification.

Flood Risk

Creation of additional flood storage and decrease in peak flood water level for the 0.5% AEP (200-year) plus CC design flood event greater than or equal to 10mm and less than 50mm.

DMRB LA 113 Magnitude Criteria and Examples – Moderate Beneficial Magnitude

DMRB LA 113 Criteria for Moderate Beneficial Magnitude is listed below:

• Results in moderate improvement of attribute quality.

The applicable scheme examples relevant for the Moderate Beneficial Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

HEWRAT assessment of both acute-soluble and chronic-sediment related pollutants becomes pass from an existing site where the baseline was a fail condition. Calculated reduction in existing spillage by 50% or more (when existing spillage risk greater than 1% annually).

Contribution to improvement in water body WFD classification.

Hydromorphology

Potential for modest improvements to channel morphology. For WFD classified water bodies, impacts may decrease the extent of morphological pressures and contributes to (but does not cause) an improvement in WFD Morphology classification.

Flood Risk

Creation of flood storage and decrease in peak flood water level for the 0.5% AEP (200-year) plus CC design flood event greater than 50mm and less than or equal to 100mm.

DMRB LA 113 Magnitude Criteria and Examples – Major Beneficial Magnitude

DMRB LA 113 Criteria for Major Beneficial Magnitude is listed below:

• Results in major improvement of attribute quality.

The applicable scheme examples relevant for the Major Beneficial Magnitude criteria is set out in the sub-sections below:

Surface Water Quality

Removal of existing polluting discharge or removing the likelihood of polluting discharges occurring to a watercourse.

Improvement in water body WFD classification.

Hydromorphology

Potential for major improvements to channel morphology. For WFD classified water bodies, impacts would decrease the extent of morphological pressures sufficiently to result in an improvement in water body WFD Morphology classification.

Flood Risk

Creation of flood storage and decrease in peak flood water level for the 0.5% AEP (200-year) plus CC design flood event greater than or equal to100mm.

Significance of Effect

Once the importance of each attribute and the magnitude of the potential impact are established, the significance of the potential effect is determined in accordance with Table 3.8.1 of DMRB LA 104 - Environmental assessment and monitoring (revision 1) (hereafter referred to as “DMRB LA 104”). This is presented as Table 13-1, with effects of ‘Moderate’ or greater regarded as significant. The matrix has been adapted from Table 3.8.1 of DMRB LA 104 and does not include a magnitude of ‘No Change’ or an importance of ‘Negligible’ as these categories are not included in DMRB LA 113.

Table 13-1: Matrix for Determining Significance of Effect

Importance	Negligible Magnitude	Minor Magnitude	Moderate Magnitude	Major Magnitude
Very High	Slight	Moderate or Large	Large or Very Large	Very Large
High	Slight	Slight or Moderate	Moderate or Large	Large or Very Large
Medium	Neutral or Slight	Slight	Moderate	Moderate or Large
Low	Neutral or Slight	Neutral or Slight	Slight	Slight or Moderate

Where the matrix indicates two alternative options (for example ‘Slight’ or ‘Moderate’), evidence would be provided which supports the reporting of a single significance category. This would be based on professional judgement, considering the importance of receptor and duration or extent of works, in accordance with the DMRB LA 104 guidance.

Assumptions and Limitations

Assumptions

The scale of the impact each improvement strategy may have on receptors is determined by the phase of the proposed scheme. The scale of impact for surface water quality receptors has been assumed to be temporary for the construction phase and permanent for the operational phase. The scale of impact for hydromorphology environment receptors has been assumed by the likely duration of the effects from each impact.

To date, there is no information on surface water outfalls. It is assumed that outfalls along the existing A75 carriageway would likely be retained and utilised for online sections of the improvement strategies. However, where offline sections of the improvement strategies are proposed, it is likely that new outfalls would be required. Where existing outfalls are to be retained for any of the improvement strategies it is assumed that appropriate treatment and flooding requirements will be factored into the wider drainage network design. Further information on the drainage design will be confirmed at DMRB Stage 2.

Limitations

The assignment of impact magnitude and potential significance for each receptor affected by the improvement strategies may be revised in subsequent DMRB stages, depending on consultation with key stakeholders and site survey data. The receptor-specific significance of effects will be confirmed as proposed scheme design details are further developed at DMRB Stage 2.

The approach of DMRB LA 113 of assigning magnitude of impact on flood risk receptors requires hydraulic modelling or detailed assessment of the design. Hydraulic modelling has not been undertaken to assess the impact of each improvement strategy on flood risk. This is considered proportionate at this early stage of assessment. The assessment of impacts is based on fluvial and surface water (pluvial) sources as the principal sources of flood risk. Groundwater flooding information will be considered during DMRB Stage 2 when further proposed scheme design information is available.

To date, no site surveys or ground investigations (GI) have been undertaken to inform this stage of assessment. This is a desktop review-based assessment using publicly available information and therefore there are data gaps. Additional information and datasets will be requested at later design stages to ensure these data gaps are covered.

At this stage, no data on abstraction or discharge licences/permissions or private water supplies has been sourced. This assessment has primarily considered publicly available information, and any additional information and datasets will be requested at DMRB Stage 2.

Study Areas

For the purposes of this assessment, a 500m buffer around each improvement strategy has been adopted for RDWE, this is shown on Figures 13-1 to 13-4 . The study areas have been assigned based on professional judgement and will allow for an assessment of potential direct effects, as well as providing a broader catchment context appropriate for the purpose of this stage of assessment. It should be noted that the study areas may increase or decrease as the proposed scheme design evolves at later assessment stages. The term ‘study areas’ has been used when referring to all/multiple improvement strategy study areas. When referring to a specific improvement strategy study area, this will be specifically mentioned.

The receptors that are outside of the RDWE study areas are assumed to not be impacted by the proposed scheme, due to distance from and/or lack of hydrological connectivity to the six improvement strategies.

Baseline Conditions

Surface Water

Hydrological Setting

The study areas lie within the Solway Tweed River Basin District. There are 19 named watercourses within the study areas. These watercourses are shown on Figure 13-1. Of these watercourses, seven are designated WFD Regulation water bodies as shown in Figure 13-2. There are also a number of other non-WFD Regulation named watercourses. Table 13-2 outlines which improvement strategy crosses each of these WFD Regulation and non-WFD regulation named watercourses.

Table 13-2: WFD Regulation and Non-WFD Regulation Named Watercourses Within the Study Areas

Watercourse	Watercourse Type	Overall Status	Relevant Improvement Strategy
Urr Water (d/s Drumhumphrey Burn)	WFD Regulation water body	Good	1, 5, 6
Spottes Burn	WFD Regulation water body	Good	1, 2, 3, 4, 5
Cargen Pow/ Bogrie Lane	WFD Regulation water body	Moderate	1, 2, 3, 4, 5
Lochfoot Burn	WFD Regulation water body	Moderate	1, 6
Under Brae Lane	WFD Regulation water body	Good	6
Culloch Burn (u/s Milton Loch)	WFD Regulation water body	Good	5
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	WFD Regulation water body	Good	6
Barnshalloch Burn	Non-WFD Regulation water body	Not applicable	None (within Improvement Strategy 1 study area)
Bettyknowes Burn	Non-WFD Regulation water body	Not applicable	1, 2
Culmain Burn	Part of Culloch Burn (Milton Loch to Kirkgunzeon Lane) WFD Regulation water body	Good	None (within Improvement Strategy 6 study area)
Larglea Burn	Non-WFD Regulation water body	Not applicable	1, 2
Glenhead Burn	Non-WFD Regulation water body	Not applicable	1, 2
Crocketford Burn	Part of Cargen Pow/ Bogrie Lane WFD Regulation water body	Moderate	1, 2, 3
Cronie Burn	Non-WFD Regulation water body	Not applicable	1, 2
Brooklands Burn	Non-WFD Regulation water body	Not applicable	1, 2
Minnydow Burn	Non-WFD Regulation water body	Not applicable	1, 2
Culshan Burn	Non-WFD Regulation water body	Not applicable	3
Barncailzie Lane	Non-WFD Regulation water body	Not applicable	3
Garmartin Burn	Non-WFD Regulation water body	Not applicable	2, 5

There are also numerous artificial drainage ditches and unnamed watercourses in the study areas. All the improvement strategies would cross over some of these minor surface water receptors.

The study areas include numerous ponds, lochs and areas of standing water of varying sizes. There are a total of four named ponds, lochs and areas of standing water. These comprise the following:

• Milton Loch is a loch located immediately-east of Improvement Strategy 5. This water body is designated under the WFD Regulations and has a ‘Moderate’ overall status.
• Auchenreoch Loch is a loch located immediately north-west of Improvement Strategies 3, 4 and 5 and is not a WFD Regulations designated water body.
• Grange Dam is a pond located in the west of Improvement Strategy 2 study area and is not a WFD Regulations designated water body.
• Brooklands Pond is located within the Improvement Strategies 1 and 2 study areas and is not a WFD Regulations designated water body.

Lochrutton Loch is also important to consider because, while not located within the study areas, it is within 50m of the southern edge of the Improvement Strategy 6 study area. Lochrutton Loch is a WFD Regulations water body with a ‘Moderate’ overall status.

Surface Water Quality

The current (2023) river water body attributes for the eight WFD Regulation water bodies in the study areas have been obtained from SEPA’s Water Classification Hub . The attributes and applicable WFD Regulation classification for the water bodies and the improvement strategies that interact with them are presented in Table 13-3 and shown in Figure 13-2.

Table 13-3: WFD Regulation Water Bodies Within the Study Areas

Watercourse	WFD Regulations Water Body ID	Length (km)/ Area (km 2 )	Heavily Modified or Artificial Water Body	Overall Ecology	Physico-chemical Status	Relevant Improvement Strategy
Urr Water (d/s Drumhumphrey Burn)	10583	20	Not designated as heavily modified	Good	High	1, 5, 6
Spottes Burn	10588	12.7	Heavily modified	Moderate	High	1, 2, 3, 4, 5
Cargen Pow/ Bogrie Lane	10600	20.9	Heavily modified	Bad	High	1, 2, 3, 4, 5
Lochfoot Burn	10601	1.9	Heavily modified	Moderate	Good	1, 6
Under Brae Lane	10602	6.3	Heavily modified	Bad	Not listed	6
Culloch Burn (u/s Milton Loch)	10592	2.3	Not designated as heavily modified	Good	Not listed	5
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	10591	11.1	Heavily modified	Poor	Good	6
Milton Loch	100330	0.6	Not designated as heavily modified	Moderate	Poor	None (within Improvement Strategy 5 study area)

Table 13-4 outlines the physico-chemical quality elements for the river water bodies within the DMRB Stage 1 Assessment Corridor and the improvement strategies that interact with them.

Table 13-4: Physico-Chemical Quality Elements of WFD Regulation River Water Bodies Within the Study Areas

WFD Regulations Water Body (ID)	Physico-Chemical Quality Elements - Temperature	Physico-Chemical Quality Elements - Dissolved Oxygen	Physico-Chemical Quality Elements - Reactive Phosphorous	Physico-Chemical Quality Elements - pH	Physico-Chemical Quality Elements - Overall	Relevant Improvement Strategy
Urr Water (d/s Drumhumphrey Burn) (10583)	High	High	High	High	High	1, 5, 6
Spottes Burn (10588)	High	High	High	High	High	1, 2, 3, 4, 5
Cargen Pow/ Bogrie Lane (10600)	High	High	High	High	High	1, 2, 3, 4, 5
Lochfoot Burn (10601)	High	High	Good	High	Good	1,6
Under Brae Lane (10602)	Not listed	Not listed	Not listed	Not listed	Not listed	6
Culloch Burn (u/s Milton Loch) (10592)	Not listed	Not listed	Not listed	Not listed	Not listed	5
Culloch Burn (Milton Loch to Kirkgunzeon Lane) (10592)	High	High	Good	High	Good	6

All of the water bodies with listed physico-chemical quality elements are currently achieving ‘Good’ or ‘High’ status. However, there are still pressures listed on Brae Under Lane, Cargen Pow/Bogrie Lane, Spottes Burn and Lochfoot Burn which are as follows:

• Modifications to bed, banks and shores from farming.
• Rural diffuse pollution.
• Invasive species pressures.

Table 13-5 outlines the physico-chemical quality elements for Milton Loch.

Table 13-5: Physico-Chemical Quality Elements of WFD Regulation Lake Water Bodies Within the Study Areas

WFD Regulations Water Body (ID)	Relevant Improvement Strategy	Physico-chemical Quality Elements - Dissolved Oxygen	Physico-chemical Quality Elements - Total Phosphorous	Physico-chemical Quality Elements - Salinity	Physico-chemical Quality Elements - Overall
Milton Loch (100330)	None (immediately south-east of Improvement Strategy 5 study area)	High	Poor	High	Poor

Pressures on Milton Loch water body are:

• Unknown pressure on water animals and plants.
• Diffuse pollution from rural sources.

Nitrate Vulnerable Zones (NVZ)

A review of Scotland’s Environment Map indicates that the study areas are not located within any NVZs. There is an NVZ in proximity, the Lower Nithsdale NVZ, located approximately 2.5 km east of Improvement Strategies 1 and 6 study areas.

Hydrology and Low Flows

The ability of a receiving watercourse to provide dilution for runoff from roads is dependent upon the flows within the watercourse whereby higher flow values indicate greater dilution potential. There are no gauging stations within the study areas available from the National River Flow Archive (NRFA). However, there is an NRFA gauging station on the Urr Water at Dalbeattie, approximately 5 km downstream of Improvement Strategy 6 study area. This station is the nearest located downstream of the study areas and provides information on a major river that flows through three of the improvement strategy study areas. Table 13-6 outlines the available information from the gauging station on the Urr Water at Dalbeattie.

Table 13-6: Flow Data for the Urr Water at Dalbeattie

Station Name	Location	Gauging Station ID Number	Q95 (m 3 /s)	BFI (Base Flow Index)	Median Flow (QMED) (m 3 /s)	Max Gauging Flow (m 3 /s)
Urr at Dalbeattie	5 km downstream of the study area at NGR NX821610	80001	0.316	0.380	88.1	120.3

Surface Water Supply

Abstractions and Discharges

No abstraction or discharge licences/permissions data has been sourced at this stage.

Drinking Water Protected Areas (DWPA)

A review of Scotland’s Environment Map indicates that there are no DWPAs within the study areas.

Private Water Supplies

No data on private water supplies have been accessed at this stage.

Hydromorphology

Aerial imagery and LiDAR data suggest that the Urr Water and Spottes Burn exhibit evidence of geomorphologically active channels. The Cargen Pow/Bogrie Lane, Culloch Burn and the Barncailzie Lane exhibit moderately active channels with moderate sinuosity and some limited geomorphological features. Other watercourses identified within the study areas are modified channels or straightened drainage ditches and lack evidence of hydromorphological processes and depositional features. Table 13-7 below details these hydromorphological receptors and the improvement strategies that they interact with.

Table 13-7: Receptors Within the Study Areas for Hydromorphology

Watercourse	Description	Importance	Justification	Relevant Improvement Strategy
Urr Water	Not designated as heavily modified with ‘Good’ overall status and ‘Good’ hydromorphological status. Existing crossings within the study area include the Old Military Road at Haugh of Urr (Grid reference (GR) NX805659), the A75 near Chapleton Farm (GR NX792663) and the Old Bridge of Urr (GR NX775677).	High	WFD Regulations water body with ‘Good’ hydromorphological status. Range of natural morphological features and processes.	1, 5, 6
Spottes Burn	Designated as heavily modified with ‘Good’ overall status and ‘Moderate’ hydromorphological status. Existing crossings within the study area include the Old Military road at Haugh of Urr (GR NX805660), the B794 (GR NX805665), a minor road bridge (GR NX805674) and the A75 (GR NX805695).	High	WFD Regulations water body with. Range of natural morphological features and processes.	3, 4, 5
Cargen Pow/Bogrie Lane	Designated as heavily modified with ‘Moderate’ overall status and ‘Bad’ hydromorphological status. Existing crossings within the study area include a minor local road (GR NX905749), a farm track (GR NX887754), a minor local road (GR NX872752), private farm roads (GR NX855739 and NX839731), is culverted under much of Crocketford and is crossed by a farm access track at (GR NX816728).	High	WFD Regulations water body.	1, 2, 3, 4, 5
Culloch Burn (u/s of Milton Loch)	Not designated as heavily modified with ‘Good’ overall status and ‘Good’ hydromorphological status. Only one existing crossing of a farm track (GR NX843729).	High	WFD Regulations water body.	5
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	Designated as heavily modified with ‘Good’ overall status and ‘Poor’ hydromorphological status. Existing crossings within the study area include two crossing of the Old Military road at Milton (GR NX848708 and NX846702) and a private farm access road (GR NX846704).	High	WFD Regulations water body.	6
Barncailzie Lane	Watercourse not designated under the WFD Regulations. Some evidence of morphological features and moderately sinuous channel in some sections. Only one existing crossing of a minor road (GR NX810707).	Medium	Water body not classified under WFD Regulations. A channel currently showing signs of historical or exiting modification and artificial constraints, attempting to recover to a natural equilibrium and exhibiting a limited range of natural hydromorphological features.	3
Other named watercourses	Watercourses not designated under the WFD Regulations. Limited evidence of morphological features with straightened and modified sections.	Low	Water bodies not classified under WFD Regulations. A channel currently showing signs of extensive historical or existing modification and artificial constraints. There is no evidence of diverse fluvial processes and morphology and active recovery to a natural equilibrium.	All
Unnamed watercourses	Primarily straightened drainage channels. No natural features likely.	Negligible	Water bodies not classified under WFD Regulations. A channel currently showing signs of extensive historical or existing modification and artificial constraints. There is no evidence of diverse fluvial processes and morphology and active recovery to a natural equilibrium.	All

Table 13-8 shows how many watercourses in total are crossed by each of the improvement strategies.

Table 13-8: Number of Water Bodies Crossed by Each Improvement Strategy

Improvement Strategy	Number of WFD Water Bodies Crossed	Number of non-WFD Water Bodies Crossed	Names of WFD Water Bodies Crossed
1	4	10	Lochfoot Burn, Cargen Pow/Bogrie Lane, Spottes Burn, Urr Water (d/s Drumhumphrey Burn)
2	2	9	Cargen Pow/Bogrie Lane, Spottes Burn
3	2	3	Cargen Pow/Bogrie Lane, Spottes Burn
4	2	2	Cargen Pow/Bogrie Lane, Spottes Burn
5	3	5	Culloch Burn (u/s of Milton Loch), Spottes Burn, Urr Water (d/s Drumhumphrey Burn)
6	4	5	Lochfoot Burn, Under Brae Lane, Culloch Burn (Milton Loch to Kirkgunzeon Lane), Urr Water (d/s Drumhumphrey Burn)

Structures are observed on numerous watercourses within the study areas, including minor and major road crossings via bridges/culverts. Scotland’s Environment Map indicates that there are no obstacles to fish migration identified within the study areas.

There are two lochs within the study areas, Milton Loch and Auchenreoch Loch. Milton Loch is approximately 0.6 km ² in area and is designated under the WFD Regulations. It has a hydromorphology status of ‘High’. Auchenreoch Loch is not designated under the WFD Regulations and is approximately 0.3km ² in area. In addition to these lochs, there are numerous smaller water bodies (such as the Grange Dam and Brooklands Pond) throughout the study areas and numerous ponds. Lochrutton Loch, while not within any of the improvement strategy study areas, is located less than 50m south of the Improvement Strategy 5 study area and has an area of approximately 0.5 km ² .

Flood Risk

Fluvial Flood Risk

A significant portion of the all the improvement strategy study areas are within the Springholm Potentially Vulnerable Area (PVA), as identified in 2018 under the National Flood Risk Assessment (NFRA) which is in the Urr water catchment. The majority of the flood risk in this area is from fluvial (river) sources.

Principal rivers with modelled flood risk have been identified using SEPA Flood Maps (hereafter referred to as “SEPA Flood Maps”) and identifying which watercourses have flood extents associated with them.

Minor watercourses have been identified through OS mapping. These include tributaries of the Urr Water such as the Garmartin Burn and two smaller unnamed tributaries upstream. A small unnamed tributary of the Spottes Burn near Hardgate has also been identified along with the Culloch Burn (u/s of Milton Loch) and the Under Brae Lane. This dataset also includes tributaries of the Cargen Pow/Bogrie Lane such as the Cronie Burn, Glenhead Burn and Lochfoot Burn as well as four other unnamed tributaries. A tributary of the Barncailzie lane to the west of Auchenreoch Loch is also apparent. Finally, the Crocketford Burn and two unnamed watercourses feeding into the northern side of Auchenreoch Loch have been identified.

SEPA Flood Maps indicate that there are areas of ‘Low’ likelihood flooding (a 0.1% (1 in 1000 year) annual exceedance probability (AEP)), ‘Medium’ likelihood flooding (a 0.5% (1 in 200 year) AEP) and ‘High’ likelihood flooding (a 10% (1 in 10 year) AEP) in the study areas. This is associated with the following watercourses:

• Urr Water
• Spottes Burn
• Barncailzie Lane
• Brooklands Burn
• Minnydow Burn
• Lochfoot Burn
• Culloch Burn (Milton Loch to Kirkgunzeon Lane)

Areas of ‘Low’, ‘Medium’ and ‘High’ likelihood flooding interact with all improvement strategies. Table 13-9 shows the approximate area of flooding within each improvement strategy as well as the water bodies where flood risk comes from. Figure 13-3 shows the ‘Low’, ‘Medium’ and ‘High’ fluvial flood extents across the study area.

Future flooding as a result of climate change is provided through the SEPA Flood Maps. This shows areas that may have a ‘Medium’ likelihood of fluvial flooding by the 2080s. This data has not been considered at this stage but will be assessed in later assessment stages.

Surface Water Flood Risk

The Springholm PVA lists surface water flooding as a potential flood source within the study areas.

The ‘Surface Water and Small Watercourses Flooding’ presented on the SEPA Flood Maps identifies areas of pluvial flood risk as well as flooding from small watercourses, field drains and areas of standing water (such as ponds and lochs).

SEPA Flood Maps indicates that there are areas of ‘Low’, ‘Medium’ and ‘High’ likelihood flooding in the study areas. Areas of ‘Low’, ‘Medium’ and ‘High’ likelihood flooding interact with all improvement strategies. Table 13-9 shows the approximate area of flooding within each improvement. Surface water flood sources primarily consist of small pockets of surface water flooding, small watercourses, field drains, from areas of standing water (for example lochs and ponds) and rainfall collecting in surface depressions in the landscape.

Figure 13-4 shows the ‘Low’, ‘Medium’ and ‘High’ surface water flood extents across the study areas.

Future flooding as a result of climate change is provided though the SEPA Flood Maps. This shows areas that may have a ‘Medium’ likelihood of surface flooding by the 2070s. This data has not been considered at this stage but will be assessed in later assessment stages.

Table 13-9: Fluvial and Surface Water Flood Risk Within the Study Areas

Improvement Strategy	Approximate Area of ‘Medium’ Probability Fluvial Flood Risk (km 2 )	Fluvial Flood Sources	Approximate Area of ‘Medium’ Probability Surface Water Flood Risk (km 2 )
1	0.30	Cargen Pow/Bogrie Lane, Minnydow Burn, Urr Water	0.40
2	0.15	Cargen Pow/Bogrie Lane, Minnydow Burn	0.15
3	0.15	Auchenreoch Loch, Spottes Burn	0.05
4	0.02	Cargen Pow/Bogrie Lane, Auchenreoch Loch, Spottes Burn	0.08
5	0.05	Spottes Burn, Urr Water	0.075
6	0.20	Spottes Burn, Urr Water	0.15

Groundwater Flood Risk

Mapping of areas susceptible to groundwater flooding will be obtained and assessed at later assessment stages.

Reservoir Flood Risk

Reservoir flood risk data will be considered at later assessment stages.

Historical Flooding

There have been historic instances of river and surface water flooding reported within the study areas. Historical fluvial (river) flooding events have been reported near Springholm and Crocketford in 2002 and 2003 and surface water flooding has been observed when heavy rainfall combined with high water levels in Auchenreoch Loch, impacting parts of the A75.

From searches of newspaper articles, there is a record of flooding in Springholm and Crocketford during Storm Frank in 2016, with a number of people being evacuated. Another, more recent, flood event occurred in January 2019, following persistent, heavy rainfall. This led to significant flooding of the A75 at Crocketford.

Other Sources

The areas are not at risk of coastal flooding due to its distance from the coast and lack of tidal influence on watercourses in the study areas. Therefore, coastal flooding has not been considered for further assessment.

The areas are not at risk of flooding from canals as there are none located within or within close proximity to the study areas. Therefore, canal flooding has not been considered for further assessment.

No sewer flooding data has been sourced at this stage. Sewer flood risk data will be requested from Scottish Water at a later assessment stage.

Potential Impacts

Construction Phase

Potential generic impacts on the water environment, which are likely to arise on typical linear infrastructure projects could arise from several direct and indirect sources during the construction of the proposed scheme. These are outlined in the sub-sections below and are applicable to all improvement strategies.

Surface Water Quality

Potential construction phase impacts include:

• The mobilisation of silts and sediments from the removal of vegetation, movement of heavy plant, runoff from haul roads and stockpiles and during earthworks (such as regrading and construction of new embankments). This could impact on the physical, chemical and microbiological water quality characteristics of receiving watercourses.
• Discharges from poor site drainage provision, washing and cleaning activities and after rainfall events that exceed the capacity of the existing drainage system.
• The risk of pollution to surface water from activities involving polluting substances such as fuels, concrete, oils, lubricants and chemicals. There is a higher risk of pollution occurring to surface waters where works occur within or immediately adjacent to a watercourse, such as during the construction or modifications of outfall structures and culverts or bridges. There is also a higher risk where works would take place close to existing gullies or drains forming part of the existing roads drainage network, creating a pathway for pollutants to reach the watercourses.
• Construction plant generating a diffuse source of hydrocarbons and to a lesser extent heavy metals, that could enter the drainage network or leach into the subsoil and find their way into watercourses. There would also be the risk of accidental spillage events from the movement of plant around the site.

Hydromorphology

Potential construction phase impacts include:

• Increase in fine sediment delivery via silt-laden runoff.
• Temporary changes to flow dynamics and regimes from the discharge of construction drainage.
• Increase in impermeable areas (hardstanding, compacted soil) during construction altering drainage networks.
• Loss of marginal or riparian vegetation adjacent to watercourses.
• Temporary change to flow dynamics and sediment transport dynamics (for example bed and/or bank scour) caused by in-channel and/or bankside works.

Flood Risk

Potential construction phase impacts include:

• Loss of floodplain storage due to construction activities taking place within the floodplain or construction compounds being located in the floodplain, resulting in increased flood risk.
• Change in flow paths due to construction activities either blocking existing or creating new flow paths, resulting in reduced channel capacity and increased flood risk.
• Works required for construction of bridges and culverts could reduce channel width if a dry working area is required within the channel and floodplain.
• Alterations to or blockage of culverts and other structures conveying water could result in a temporary loss of capacity resulting in increased flood risk.
• The temporary increase in impermeable surface due to haul routes or construction compounds during construction could lead to increased surface water volume and rates of runoff, resulting in increased flood risk.
• Water abstracted from groundwater control activities or dewatering could be discharged to nearby watercourses or back to groundwater through a recharge arrangement. This could lead to a temporary localised increase in flood risk.

Operational Phase

Potential generic impacts on the water environment, typical of linear infrastructure projects could arise from a number of direct and indirect sources during the operation as detailed in the sub-sections below and are applicable to all improvement strategies.

Surface Water Quality

Potential operational phase impacts include:

• New discharges of road runoff, shading by new structures and vegetation and use of herbicides could cause changes to dissolved oxygen levels and temperature.
• Pollutants in road runoff such as oils and hydrocarbons from fuel combustion, and metals such as copper and zinc from vehicles would be deposited on the road surfaces. This road runoff would enter watercourses with a potential to cause water pollution and impact both the chemical and biological water quality or receiving watercourses.
• Pollutants, when combined with rainfall, can run-off into the road drainage system and have an adverse effect on the receiving watercourses. There are a number of factors which influence both the pollutant concentrations in routine runoff and whether the runoff is likely to have an impact on the receiving water body.
• Suspended sediments in road runoff associated with larger and/or new impermeable areas could lead to sediment pollution in receiving watercourses.
• De-icing materials such as road salt could impact the chemical and biological quality of receiving watercourses.

Hydromorphology

Potential operational phase impacts include:

• New alignment of watercourses could cause changes in flow regime. Changes in channel gradient could alter flow and sediment erosion/deposition processes.
• New drainage (such as outfall structures or change to discharges) could result in loss of riparian vegetation around structures or removal of a length of natural channel bank (if an outfall is required).
• New discharges (from outfalls) could cause localised changes in flow regime within the channel with the potential to alter local substrate structure by erosion of the bed or banks. Potential to alter existing morphological features.
• New crossings have the potential to change the volume and rate of surface water runoff (including riparian drainage) entering a channel, potentially affecting the flow regime and sediment erosion/deposition processes within the channel.
• Extended culverts have the potential to lead to a loss of bed and bank material.
• New culverts have the potential to alter bed substrate, flow dynamics, flow velocities and sediment mobilisation/transport processes.
• Earthworks might result in reduction in lateral connectivity between watercourses and their riparian zone and floodplain, where embankments are in close proximity to watercourses.
• Increase of impermeable surfaces might result in altering the local drainage network and increasing surface water runoff leading to changes in sediment erosion/deposition processes and channel adjustment.

Flood Risk

Potential operational phase impacts include:

• Changed flow paths due to operation resulting in either the blocking of existing flow paths or the creation of new flow paths, resulting in increased flood risk.
• Any new river crossings could reduce channel conveyance. Extended culverts have increased chance of blockages.
• Permanent increase in impermeable areas during operation resulting in increased surface water runoff volume and rate, resulting in an increased risk of flooding.
• Loss of floodplain storage due to infrastructure encroaching into the floodplain, resulting in increased flood risk.
• Alterations to or blockage of culverts and other structures conveying water could result in a temporary loss of capacity resulting in increased flood risk.
• Cuttings may provide a route ingress for groundwater, potentially placing the new road at risk.

Design, Mitigation and Enhancement Measures

Embedded Mitigation Measures

Embedded mitigation for all improvement strategies would be integrated into the design as the proposed scheme progresses.

Mitigation Measures – Construction Phase

The sub-sections below provide an overview of potential mitigation measures that could be applied to mitigate the impacts for surface water quality, surface water supply, hydromorphology and flood risk during construction. It should be noted, this is a preliminary assessment based on the improvement strategies. Alternative and bespoke mitigation measures could be required as the proposed scheme progresses.

Many of the construction mitigation measures set out in the sub-sections below would be secured via the production and implementation of an Environmental Management Plan (EMP). These are applicable to all improvement strategies.

Surface Water Quality

Potential construction phase mitigation measures include:

• Undertake work in line with good practice for pollution prevention and relevant code of construction practices.
• Develop an Emergency Pollution Response Plan in accordance with guidance for pollution prevention.
• Programme and sequence activities to ensure work within the watercourses is undertaken during periods of low flow to reduce the risk of scour/erosion mobilising fine sediments around the riverbed and/or structure.
• Drainage to prioritise the use of Sustainable Drainage Systems (SuDS) where practicable. Runoff from the haul roads should be attenuated then discharged in accordance with the drainage hierarchy. As such, in line with the drainage hierarchy discharge to ground should be sought first. Where this is not practicable, discharge to watercourse then surface water sewer would be considered.

Hydromorphology

Potential construction phase mitigation measures include:

• Undertake work in line with good practice for pollution prevention and relevant code of construction practices.
• Programme and sequence activities to ensure work within the watercourses is undertaken during periods of low flow to reduce the risk of scour/erosion mobilising fine sediments around the riverbed and/or structure.
• During any modifications to culverts or other crossings, allow the watercourse to continue to flow, for example using a flume.
• Where practicable, avoid/minimise any in-channel working, including avoidance of key migratory periods for fish; and minimise any removal of riparian and bankside vegetation. Where practicable, replant any lost riparian vegetation.
• Limit the extent of vegetation clearance to only the minimum areas necessary to reduce sediment input during clearance and from bare ground following clearance.
• Locate construction activities (including stock piling, construction compounds and vehicle washing) at suitable distances away from watercourses.
• Any watercourse realignments would be constructed offline to allow the existing watercourse to continue to flow. These would also be appropriately tied into the existing watercourse to reduce the risk of significant channel adjustment and/or bed and bank scour.

Flood Risk

Potential construction phase mitigation measures include:

• Locate work areas outside the floodplain where possible. Where this is not possible, temporary floodplain compensation may be required to offset storage losses.
• Design site areas to avoid changing fluvial and surface water flow routes where possible. Use permeable surfaces in compounds.
• Temporary dewatering may be required for below ground works, any discharges may need to be attenuated, or paused during flood events to prevent increase in risk elsewhere.
• Provide attenuation storage within site drainage to restrict runoff to existing rates.
• Construction in areas at high risk to take place during period of reduced fluvial flood risk (spring/summer), where reasonably practicable.
• New crossings should be designed to accommodate temporary increases to flood risk in addition to a pre-determined flood risk.
• Sign up to Scotland’s Flood Forecast and develop a flood response plan.

Mitigation Measures – Operational Phase

The following sub-sections provide an overview of potential mitigation measures that could be applied to mitigate the impacts for surface water quality, surface water supply, hydromorphology and flood risk during operation. It should be noted, this is a preliminary assessment based on the improvement strategies. Alternative and bespoke mitigation measures could be required as the proposed scheme progresses. These would be applicable to all improvement strategies.

Surface Water Quality

Potential operational phase mitigation measures include:

• The drainage design would incorporate mitigation measures to treat and attenuate road runoff (such as SuDS features) to the standard required by DMRB LA 113 and other standards contained within the DMRB.
• Following the SuDS hierarchy, discharges to ground are preferable if determined to be feasible and appropriate through a risk assessment, with appropriate treatment provided where necessary. Where this is not practicable, road runoff would be treated and attenuated prior to discharge.

Hydromorphology

Potential operational phase mitigation measures include:

• The drainage design should aim to avoid discharges of routine runoff to the smaller watercourses where practicable.
• At this stage outfalls have not been assessed, but in the instance that new outfalls are required they should remain compliant with good guidance and design standards. They would be designed to mitigate impacts on hydromorphology, therefore aligned downstream at a 45° angle, submerged below the water line, if practicable, and attenuate flows to match existing discharge rates along the receiving watercourse.
• Design of permanent structures (such as culverts, bridges, and outfalls) in line with good practice and CIRIA guidance including facilitating fish passage and the use of soft-engineering techniques where practicable to mitigate impacts on hydromorphology.
• Any potential channel realignments would be appropriately tied into the existing watercourse to reduce the risk of significant channel adjustment and/or bed and bank scour.
• For the assumed bridges, consider a clear span structure so abutments are set back from the channel banks and do not impact in-channel hydromorphological processes.
• Avoiding removal of water features through appropriate proposed scheme design. Potential for addition of morphological features in watercourses to provide habitat enhancement.

Flood Risk

Potential operational phase mitigation measures include:

• Structures to be designed outside the floodplain where possible. Where this is not possible, clear span structures should be considered to minimise effects as far as practicable. Bridges to be sized taking into account climate change over the life of the structure. Compensatory flood storage may be required to offset floodplain losses that result from the proposed scheme.
• Drainage to prioritise the use of SuDS where practicable. Runoff from the carriageways should be attenuated then discharged in accordance with the drainage hierarchy. As such, in line with the drainage hierarchy discharge to ground should be sought first. This is dependent on the geology of the land and the risk of the water being a pollutant. Where this is not practicable, discharge to watercourse then surface water sewer will be considered. This is to prevent increased flood risk elsewhere.
• Provision of crossings or culverts to maintain existing surface water overland flow paths.
• Regularly inspect and maintain drainage infrastructure for defects and blockages to ensure they remain effective.
• Where required, drainage design to restrict discharge rates and volumes to ensure no increase in flood risk as a result of increased impermeable area.

Enhancement Measures

Enhancement Measures – Construction Phase

There is no potential enhancement measures identified for the construction phase at this stage. This is applicable to all improvement strategies. However, further potential enhancement measures may be identified in later assessment stages.

Enhancement Measures – Operational Phase

Potential enhancement measures that could be incorporated into the design, which would be applicable to all improvement strategies, and would be effective during the operation phase may include:

• Consideration of the use of new embankments or larger drainage measures to intercept and attenuate flood flows to reduce flood risk downstream.
• Provision of treatment facilities (such as SuDS) to improve surface water quality beyond that required to meet statutory water quality standards, or provision of treatment of water quality where none currently exists.
• Install additional pollution prevention measures for existing drainage systems.
• The opening up (daylighting) of existing culverts can improve the water quality, fish passage and hydromorphology of watercourses.
• Removal or reconstruction and improvement of existing crossings to make more environmentally sympathetic crossings.
• Indirect landscape enhancements to the existing landscape via Biodiversity Net Gain (BNG) in-channel improvements.
• Identifying and implementing needed environmental improvements based on River Basin Management Plans (RBMPs).

Assessment of Likely Significant Effects

Construction Phase

Surface Water Quality

Construction activities, particularly those requiring in-channel works or extensive works in proximity to the proposed road structure, have the potential to result in significant effects on surface water quality of the watercourses in the study areas in the absence of mitigation.

These impacts are largely associated with the construction of bridges, new outfalls, culverts and their extensions that are proposed near to, or on a channel meander or an extensive section of the proposed road structure. Culverts are more likely to require in-channel works than bridges.

Typically, improvement strategies with a greater number and extent of in-channel works result in greater effects on surface water during construction. Table 13-10 shows the significance of construction phase effects (pre-mitigation) on the surface water quality receptors within the study areas. The construction phase effect considered in this instance is the release of fine sediments and pollutants from construction runoff and other construction activities (for example use and fuelling of plant, runoff from stockpiles and stripped land).

Table 13-10: Significance of Construction Phase Effects (Pre-Mitigation) on Surface Water Quality Receptors Within the Study Areas

Receptor	Importance	Relevant Improvement Strategy	Magnitude of Impact	Significance
Urr Water	High	1, 5, 6	Major Adverse	Large or Very Large
Spottes Burn	High	1, 2, 3, 4, 5	Major Adverse	Large or Very Large
Cargen Pow/Bogrie Lane	High	1, 2, 3, 4, 5	Major Adverse	Large or Very Large
Lochfoot Burn	High	1, 6	Major Adverse	Large or Very Large
Under Brae Lane	High	6	Major Adverse	Large or Very Large
Culloch Burn (u/s of Milton Loch)	High	5	Major Adverse	Large or Very Large
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	High	6	Major Adverse	Large or Very Large
Milton Loch	High	None (immediately south-east of Improvement Strategy 5 study area)	Moderate Adverse	Moderate or Large
Other named watercourses	Medium	All improvement strategies	Moderate Adverse	Moderate
Unnamed watercourses	Low	All improvement strategies	Moderate Adverse	Slight

Subject to the implementation of appropriate mitigation measures (to be listed in an EMP), it is anticipated that there would be no significant adverse effects on surface water quality during the construction phase.

Surface Water Supply

As is typical at DMRB Stage 1, an assessment of the likely significant effects for the construction phase for surface water supply cannot be undertaken due to a lack of detailed information. Therefore, this sub-element of the RDWE assessment has been retained and will be fully assessed at DMRB Stage 2 when the relevant information and datasets will be acquired.

Hydromorphology

In the absence of mitigation measures, construction activities, particularly those requiring in-channel works or extensive works near water bodies, have the potential to result in significant impacts on the hydromorphology of the water bodies within the study areas. These impacts are largely associated with the construction of bridges, new outfalls, culverts, and their extensions. Table 13-11 shows the significance of construction phase effects (pre-mitigation) on the hydromorphology receptors within the study areas. The construction phase effect considered in this instance is the temporary alterations to the bed and banks of watercourses and release of sediment during construction with the potential to alter morphological features, sediment dynamics and flow dynamics.

Table 13-11: Significance of Construction Phase Effects (Pre-Mitigation) on Hydromorphology Receptors Within the Study Areas

Receptor	Importance	Relevant Improvement Strategy	Magnitude of Impact	Significance
Urr Water	High	1, 5, 6	Major Adverse	Large or Very Large
Spottes Burn	High	3, 4, 5	Moderate Adverse	Moderate or Large
Cargen Pow/Bogrie Lane	High	1, 2, 3, 4, 5	Moderate Adverse	Moderate or Large
Culloch Burn (u/s of Milton Loch)	High	5	Major Adverse	Large or Very Large
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	High	6	Minor Adverse	Slight or Moderate
Barncailzie Lane	Medium	3	Minor Adverse	Slight
Other named watercourses	Low	All improvement strategies	Minor Adverse	Slight
Unnamed watercourses	Low	All improvement strategies	Minor Adverse	Slight

Subject to the successful implementation of mitigation measures (to be listed in an EMP), it is anticipated that there would be no significant adverse effects on hydromorphology during the construction phase.

Flood Risk

All improvement strategies cross ‘Low’, ‘Medium’ and ‘High’ likelihood flood extents for fluvial and surface water flooding. Therefore, all improvement strategies could impact flood risk from these sources during construction.

All improvement strategies are likely to require drainage upgrades to attenuate the increased runoff rates, including the possibility of new outfalls into watercourses, involving in-channel works or temporary dewatering. The extent of additional drainage requirements is unknown at this stage, but any in-channel works would require mitigation to avoid altering channel capacity or flows.

Construction compound/s have not been confirmed at this stage, but it is unlikely that they would be located within areas of ‘Medium’ or ‘High’ likelihood flooding. If it is not possible to locate the construction compound/s outside of these flood risk areas, additional mitigation would be required to mitigate the impacts of potential temporary floodplain reduction.

The creation of construction compounds and access tracks would require the compaction of land to create level surfaces. This would interfere with infiltration rates and increase runoff rates. Additional temporary attenuation or dewatering may be required to mitigate increased levels of runoff.

Below ground works have the potential to disrupt below ground level flows and infiltration rates, which may increase groundwater flood risk elsewhere. Any below ground level works could require mitigation to divert flows elsewhere. It is unknown at this stage whether below ground works would be required for the improvement strategies.

Without mitigation, construction could have significant effects that impact flood risk through temporary alteration of surface water and below ground flow paths, decreased floodplain storage, increased rates of runoff and the potential for in-channel works. It is assumed that post-construction, access routes and compound areas would be returned to their existing condition and therefore any effects would be temporary and not significant.

The flood risk receptors are presented with their importance in Table 13-12.

Table 13-12: Importance Assignment of Flood Risk Receptors in the Study Areas

Receptor	Importance
A75, A712, B794 and B795	Essential infrastructure
Residential properties, schools, hotels and village halls	More vulnerable
Buildings used for shops or general industry, storage and distribution; land used for agriculture; local roads	Less vulnerable
Amenity open space	Water compatible

It should be noted that flood risk magnitude and significance, as outlined in the Magnitude section of this chapter, has not been assigned at this stage. This is because it is not possible for increases in flood levels to be ascertained from the available data. The magnitude and significance will be assigned at subsequent design stages when further information is requested and assessed.

At this stage, subject to the implementation of mitigation measures (to be listed in an EMP), it is anticipated that post-mitigation, there would be no significant adverse effects on flood risk during the construction phase.

Operation Phase

Surface Water Quality

In the absence of mitigation measures, for all improvement strategies, there is potential for significant effects from polluted runoff entering the roads drainage system which discharges into watercourses. There is also the risk of accidental spillages.

There are eight WFD Regulations water bodies within the study areas, seven of which interact with the improvement strategies. This means that there is the potential for direct impacts on these WFD Regulations water bodies. Furthermore, there is potential for indirect impacts on Milton Loch water body as the Culloch Burn (u/s of Milton Loch), which is impacted by Improvement Strategy 5, feeds into the loch. There are also a number of named and unnamed watercourses that are directly impacted by the improvement strategies. Table 13-13 shows the significance of operational phase effects (pre-mitigation) on the surface water quality receptors within the study areas. The operational effect considered in this instance is polluted runoff or accidental spillages from new road surfaces entering the road drainage system and entering into watercourses.

Table 13-13: Significance of Operational Phase Effects (Pre-Mitigation) on Surface Water Quality Receptors Within the Study Areas

Receptor	Importance	Relevant Improvement Strategy	Magnitude of Impact	Significance
Urr Water	High	1, 5, 6	Major Adverse	Large or Very Large
Spottes Burn	High	1, 2, 3, 4, 5	Major Adverse	Large or Very Large
Cargen Pow/Bogrie Lane	High	1, 2, 3, 4, 5	Major Adverse	Large or Very Large
Lochfoot Burn	High	1, 6	Major Adverse	Large or Very Large
Under Brae Lane	High	6	Major Adverse	Large or Very Large
Culloch Burn (u/s of Milton Loch)	High	5	Major Adverse	Large or Very Large
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	High	6	Major Adverse	Large or Very Large
Milton Loch	High	None (immediately south-east of Improvement Strategy 5 study area)	Moderate Adverse	Moderate or Large
Other named watercourses	Medium	All improvement strategies	Moderate Adverse	Moderate
Unnamed watercourses	Low	All improvement strategies	Moderate Adverse	Slight

Surface Water Supply

As is typical at DMRB Stage 1 an assessment of the likely significant effects for the operational phase for surface water supply cannot be undertaken due to a lack of detailed information. Therefore, this sub-element of the RDWE assessment has been retained and will be fully assessed at later assessment stages when the relevant information and datasets will be acquired.

Hydromorphology

The operation of culverts, bridges and outfalls have the potential to result in significant impacts on the hydromorphology of the watercourses in the study areas. The associated operational effects of these should be minimal if good design practice is implemented. Table 13-14 shows the significance of operational phase effects (pre-mitigation) on the hydromorphology receptors within the study areas. The operational effect in this instance relates to the operation of culverts, bridges and outfalls. This could represent a change to the morphological condition, sediment dynamics and flow dynamics of the watercourse.

Table 13-14: Significance of Operational Phase Effects (Pre-Mitigation) on Hydromorphology Receptors Within the Study Areas

Receptor	Importance	Relevant Improvement Strategy	Magnitude of Impact	Significance
Urr Water	High	1, 5, 6	Major Adverse	Large or Very large
Spottes Burn	High	3, 4, 5	Moderate Adverse	Moderate or Large
Cargen Pow/Bogrie Lane	High	1, 2, 3, 4, 5	Moderate Adverse	Moderate or Large
Culloch Burn (u/s of Milton Loch)	Medium	5	Major Adverse	Moderate or Large
Culloch Burn (Milton Loch to Kirkgunzeon Lane)	Medium	6	Minor Adverse	Slight
Barncailzie Lane	Medium	3	Minor Adverse	Slight
Other named watercourses	Low	All improvement strategies	Minor Adverse	Slight
Unnamed watercourses	Low	All improvement strategies	Minor Adverse	Slight

There are notable significant effects for all improvement strategies, especially those requiring significant offline realignment with a large number of new watercourse crossings (Improvement Strategies 1, 2, 4, 5 and 6). New crossings have the potential to lead to changes in flow dynamics and sediment transport dynamics which in turn may lead to channel instabilities propagating upstream and downstream of the proposed crossings.

Improvement Strategy 3 would have the least significant effects due to it being primarily an online realignment of the existing A75 carriageway and not requiring any additional crossings of any watercourses in the Improvement Strategy 3 study area. However, this improvement strategy would potentially require an extension to existing culverts, widening of existing bridges and additional culverts to accommodate these changes.

Flood risk

All improvement strategies involve permanent land take within mapped areas of flood risk. This could result in a decrease in floodplain storage and displaced flood water. Mitigation would be required to provide additional, permanent floodplain storage, to reduce the significance of effects.

All improvement strategies would involve permanent increases in impermeable surface area from widening of existing carriageways to the creation of new carriageways. This would increase the runoff rates. Assuming the existing drainage network would not have capacity, additional drainage upgrades would be required to attenuate the increased runoff rates for all improvement strategies. The extent of additional drainage requirements is unknown at this stage.

Permanent below ground features such as retaining walls can alter below groundwater flows and if not properly mitigated, cause groundwater flooding elsewhere. It is unknown at this stage if any permanent below ground features are required for the improvement strategies. Should below ground features be required post construction, additional mitigation would be implemented to reroute any flows, if necessary.

The flood risk receptors are presented with their importance in Table 13-12.

It should be noted that flood risk magnitude and significance has not been assigned at this stage. This is because it is not possible for increases in flood levels to be ascertained from the available data. The magnitude and significance will be assigned at subsequent design stages when further information is requested and assessed.

In addition, further assessment may be needed following confirmation of proposed scheme design. Embedded and additional mitigation would be expected to eliminate any proposed scheme-induced increases in flood risk.

No significant flood risk impacts are anticipated as a result of the improvement strategies. It should be noted that any potential increase in flood risk to third parties, regardless of the significance of effect, may need to be mitigated to comply with planning policy.

Proposed Scope of Future Assessment

The assessment for future DMRB stages will require additional, more detailed datasets and design information to quantify the impacts of the proposed scheme on the surrounding water environment. The types of datasets required have been identified through various sections of this report and will be requested from the relevant authority at subsequent DMRB stages. A more robust assessment of the improvement strategies will be carried out during future DMRB stages with reference to additional data and design information.

The main objective of the assessment will be to ensure that:

• The need for the avoidance and reduction of impacts on the water environment is accounted for in the selection of improvement strategies and environmental evaluation of the proposed scheme.
• The selection of appropriate mitigation measures against any significant predicted impacts of the improvement strategies is made with the aim to design out potential adverse environmental impacts.

Summary

The RDWE assessment reviewed a range of baseline data to identify relevant surface water, hydromorphology and flood risk receptors within the study areas.

The assessment was undertaken in accordance with relevant industry guidance to identify the potential effects on these receptors and their significance from the implementation of the proposed scheme. Table 13-15 shows the potential significant effects identified (pre-mitigation) for the sub-elements of the RDWE. All sub-elements of the RDWE DMRB Stage 1 Assessment have been scoped in for both the construction and operation phases and will be assessed as part of DMRB Stage 2. Surface water supply has not been assessed due to the high-level information available at this stage in the process. This sub-element has been retained for full assessment at DMRB Stage 2.

Table 13-15: Scope of the RDWE Assessment for DMRB Stage 1

Sub-element	Effect Identified (Construction Phase)	Effect Identified (Operational Phase)	Improvement Strategy	Potential Significance of Effect (pre-mitigation) (Construction and Operational phases)
Surface water quality	Release of fine sediments and pollutants from construction runoff and other construction activities (for example use and fuelling of plant, runoff from stockpiles and stripped land).	Polluted runoff/accidental spillages from new road surfaces entering the road drainage system and entering into watercourses.	All improvement strategies	Large or Very Large
Hydromorphology	Temporary alterations to the bed and banks of watercourses and release of sediment during construction with the potential to alter morphological features, sediment dynamics and flow dynamics.	Operation of culverts, bridges and outfalls, representing changes to the morphological condition, sediment dynamics and flow dynamics of the watercourse.	1 2 3 4 5 6	Large or Very Large Moderate or Large Moderate or Large Moderate or Large Large or Very Large Large or Very Large
Flood risk	Temporary decreases in floodplain storage and displacement of flood water.	Decrease in floodplain storage and displacement of flood water.	All improvement strategies	To be determined at later design stage
Flood risk	Compaction of land to create level surfaces leading to changes in infiltration rates and increased runoff rates.	Increases in runoff rates due to increases in impermeable areas.	All improvement strategies	To be determined at later design stage
Flood risk	Alteration of below ground level flows potentially leading to groundwater flooding elsewhere.	Alteration of below ground level flows potentially leading to groundwater flooding elsewhere.	All improvement strategies	To be determined at later design stage
Flood risk	Potential for in-channel works in areas of flood risk	Alteration of below ground level flows potentially leading to groundwater flooding elsewhere.	All improvement strategies	To be determined at later design stage

The identified effects on RDWE, as shown in Table 13-15, are those considered without mitigation. Some of these effects would be mitigated using the measures outlined in the Design, Mitigation and Enhancement Measures section of this chapter. At later design stages, as more detailed design information becomes available, additional mitigation measures, including embedded mitigation, may be required to reduce any potential effect as far as reasonably practicable.