Harrogate BC - Level 2 SFRA

FINAL

August 2013

Harrogate Borough Council Department of Development Services Knapping Mount West Grove Rd Harrogate North Yorkshire HG1 2AE www.harrogate.gov.uk/planning

JBA Project Manager

Judith Stunell JBA Consulting Bank Quay House Sankey Street WARRINGTON WA1 1NN Revision History

Revision Ref / Date Issued Amendments Issued to

11/01/12 Draft report for Pateley Linda Marfitt Bridge and Masham sites 26/07/12 Revised Pateley Br and Linda Marfitt Masham with Linda Marfitt review comments. Added draft for site R32 29/05/2013 Added report section for Linda Marfitt, Simon site R10 Hartley (Harrogate BC) 28/08/2013 Revised following HBC Simon Hartley (Harrogate review comments. BC)

Contract

This report describes work commissioned by Dave Allenby, on behalf of Harrogate Borough Council, by a letter dated 01 September 2011. Harrogate BC’s representative for the contract was Linda Marfitt. Kevin Frodsham, Julia Hunt, Andy Wood and Judith Stunell of JBA Consulting carried out this work.

Prepared by ...... Judith Stunell BSc PhD CEnv MCIWEM C.WEM Principal Analyst

Prepared by ...... Andrew Wood BSc MSc PhD CEng MICE Senior Engineer

Prepared by ...... Kevin Frodsham BSc DipMath MSc PhD FGS ARSM Senior Analyst

Reviewed by ...... Gary Deakin BSc CEng MICE Director

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Purpose

This document has been prepared for Harrogate Borough Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared. JBA Consulting has no liability regarding the use of this report except to Harrogate Borough Council.

Acknowledgements

Dan Normandale (Environment Agency), Mike Wickens (Harrogate BC) and Mark Young (North Yorkshire County Council) have provided very helpful advice and information during preparation of this report. Copyright

© Jeremy Benn Associates Limited 2013 Carbon Footprint

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Executive Summary

The Harrogate Borough Council Level 2 SFRA provides a more detailed assessment of four areas that were identified as a risk of flooding in the Level 1 SFRA but where Harrogate BC have need for regeneration and wider development in their plans. This forms part of the evidence that officers use to make recommendations to members. The key objectives are to assess whether development on these sites could be made safe and to provide recommendations for detailed Flood Risk Assessments (FRA) and potential measures to mitigate flood risk. The sites are: Pateley Bridge (site P3001) on the East Bank of the River Nidd The risk of flooding at this site from the River Nidd has found to be low, due to the existing defences which are in good condition. There is a risk of surface water flooding with runoff from the surrounding area ponding on the site. With careful site design based on a detailed FRA and adequate mitigation for any development in parts of the site at risk of flooding it is likely that development on this site could be made safe. Masham (sites M1 and M3002) Masham has a history of flooding from Swinney Beck. Site M1 has been observed to be on a flow path from Swinney Beck to the River Ure. There is the potential for deep flooding on site M1 (>1m) with fast flowing floodwater. The average hazard category on the site in a 1% AEP event is ‘Danger to Most’. Access routes are also flooded and evacuation of the site/ emergency access could be dangerous. It would be difficult to make development on this site safe and avoid increasing flood risk elsewhere. The risk at site M3002 is lower although 62% of the site is in either flood zone 2 or 3. The average depth of flooding in a 1% event is relatively low (<0.2m) and the overall hazard is ‘very low’. There may be issues with access during a flood event as the model suggests deep flooding around the access points at Swinney Beck Bridge and Foxholme Lane. It is likely that development on this site could be made safe if it was located in the parts of the site that are not at risk of flooding and issues around site access during a flood event were addressed in the development design, FRA and mitigation measures. Ripon – Site R10 (Auction Mart) The Auction Mart site is at risk of flooding from the River Ure and the River Skell in a 0.1% AEP flood event with more than 50% of the site at risk. Although this is an extreme event the site forms part of a floodplain conveyance route with deep water (>1.5 m) flowing quickly across the site. The site benefits from defences on both the River Ure at North Bridge and the River Skell which reduce the depth and velocity of flood water but not the flood extent. The risk from each river has been assessed separately and both events have a Hazard category of ‘Danger to All’. Development on this site would need very careful design based on a detailed FRA and consideration of the variation in hazard across the site. The volume of water flowing across the site in a large flood event could be displaced by any development and would increase flood risk elsewhere. It is recommended that the detailed FRA should investigate joint flood events on both the river Skell and Ure. Ripon – Bishopton (Site R32) Investigation of flood risk at this site has found that only a small proportion of the site is flooded in both a 1% and 0.1% AEP. The site slopes steeply towards the River Laver and there is the potential for surface water flooding as water runs down towards the river, this should be considered in the site layout and landscaping. There is a risk that development on the site could displace floodwater and the modelling work found that raised ground levels on the site increased flow over the opposite bank of the river onto the adjacent flood plain. This should be considered in a FRA based on detailed representation of the nearby floodplain. It is recommended that development on the site avoids the areas at risk of flooding.

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Flood Risk Assessment and Development Recommendations For each site a set of development recommendations have been made. These follow a set of general principles which should be considered for safe development and mitigation of any risks that cannot be avoided. These are: • Avoid development in parts of sites that are at risk of flooding, this reduces the risk of flooding at the development or of displaced water increasing the risk of flooding elsewhere. This follows the principles of the National Planning Policy Framework (NPPF) and its accompanying technical paper • If development takes place in areas at risk of flooding then the development layout should be designed to avoid the highest risk areas. This should include a detailed assessment of vulnerability across the site based on depth, velocity, people and place vulnerability. The design should include mitigation measures (e.g. raised floor levels, no ground floor accommodation). • Consider the access routes to the site and design these to avoid the areas of highest flood risk to ensure that the development can be safely evacuated in a flood event • Where available occupiers of sites at risk of flooding should sign up to the Environment Agency’s flood warning services.

Recommendations for flood risk assessment have also been made for each site. Flood Risk assessments should use detailed investigation and modelling of the site and its surrounding area to assess issues such as: • The risk of flooding of the development • The impact of any displaced water on flood risk elsewhere. This may be water from rivers, surface runoff or sewers. • The impact of the development on runoff patterns either to local watercourses or to sewers and existing drainage infrastructure • The flood hazard and vulnerability, and whether this can be managed • Access routes and their safety, any other emergency planning requirements (e.g. Flood Warning)

Flood Risk Assessments are site specific and depend on the details of the development and the site. It is recommended that developers use the FRA process to inform safe development, demonstrate that the site can pass the exception test and design any mitigation measures that are required.

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Contents

Executive Summary ...... iii 1 Introduction ...... 1 1.1 Background ...... 1 1.2 Scope and Objectives ...... 1 1.3 Study Area ...... 1 1.4 Outline Methodology ...... 6 2 Flood Risk Review ...... 8 2.1 River Nidd at Pateley Bridge ...... 8 2.2 Swinney Beck at Masham ...... 11 2.3 Ripon - River Ure, River Laver and River Skell ...... 12 3 Pateley Bridge ...... 14 3.1 Introduction ...... 14 3.2 Existing Risk - River Flooding ...... 15 3.3 Role of Defences - River Flooding ...... 16 3.4 Impact of Development ...... 20 3.5 Climate Change Impacts ...... 20 3.6 Surface Water Drainage and Flood Risk ...... 20 3.7 Exception Test Summary...... 21 3.8 Recommendations for the Preparation of Flood Risk Assessments ...... 23 3.9 Development Recommendations ...... 25 4 Masham...... 26 4.1 Introduction ...... 26 4.2 Existing Risk ...... 28 4.3 Impact of Development on Flood Risk ...... 35 4.4 Updated Level 1 Table for Site M3002 ...... 35 4.5 Surface Water Drainage and Flood Risk ...... 37 4.6 Summary ...... 38 4.7 Exception Test Summary...... 39 4.8 Flood Risk Assessment Recommendations ...... 41 4.9 Development Recommendations ...... 42 5 Ripon – Auction Mart Site (R10) River Ure and River Skell ...... 44 5.1 Introduction ...... 44 5.2 Flood Risk from Rivers ...... 46 5.3 Flood Risk from the River Ure ...... 47 5.4 Flooding from the River Skell ...... 50 5.5 Summary of fluvial flood risk to the site ...... 53 5.6 Surface Water Flood Risk ...... 54 5.7 Climate Change ...... 56 5.8 Impact of Development on Flood Risk Elsewhere ...... 56 5.9 Exception Test Summary...... 56 5.10 Flood Risk Assessment Recommendations ...... 57 5.11 Development Recommendations ...... 58 6 Ripon - River Laver at Bishopton ...... 59 6.1 Introduction ...... 59 6.2 Existing Flood Risk ...... 60 6.3 Climate Change ...... 64 6.4 Impact of Development on Downstream Flood Risk ...... 64 6.5 Surface Water Drainage and Flood Risk ...... 64 6.6 Exception Test Summary...... 66

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Contents

6.7 Recommendations for the Preparation of Flood Risk Assessments ...... 66 6.8 Development Recommendations ...... 68 Appendices...... I A Appendix - Sustainable Drainage Systems...... I References...... V

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List of Figures

Figure 1-1 Pateley Bridge Site Location and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue) ...... 2 Figure 1-2 Masham Potential Sites and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue) ...... 3 Figure 1-3 Ripon River Ure Site and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue) ...... 4 Figure 1-4 Bishopton Site and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue) ...... 5 Figure 2-1 Site P3001 and the Environment Agency Flood Zones ...... 8 Figure 2-2 Structures Influencing Flood Risk at P3001 ...... 9 Figure 2-3 Pateley Bridge Flood Defences ...... 10 Figure 2-4 Structures Influencing Flood Risk at Site M3002 and Site M1 ...... 11 Figure 2-5 Bishopton Site and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue) ...... 12 Figure 3-1 Existing Risk in Pateley Bridge ...... 15 Figure 3-2 - Modelled Undefended Flood Depth Maps ...... 16 Figure 3-3 Embankment near modelled breach location ...... 17 Figure 3-4 Modelled Local Breach Flood Depth Maps ...... 18 Figure 3-5 Failure of Floodgate ...... 19 Figure 3-6 Pateley Bridge Surface Water Flood Map and historical records ...... 21 Figure 4-1 Sites M1 and M3002 in Masham ...... 27 Figure 4-2 Masham Flood Zones ...... 28 Figure 4-3 Masham 2004 JFLOW outlines ...... 29 Figure 4-4 Peak Depth of Flooding (JFLOW) ...... 30 Figure 4-5 Flood Velocities (JFLOW) ...... 32 Figure 4-6: Danger to People from Depth and Velocity (table 13.1 from FD 2320 Flood Risk Assessment Guidance for New Development Phase 2 Defra/EA Flood & Coastal Defence R&D Programme TR2 (Technical Report 2), October 2005) ...... 33 Figure 4-7: Surface Water Flood Map ...... 38 Figure 5-1 Site R10 Location ...... 44 Figure 5-2 Site R10 topography ...... 45 Figure 5-3 Observed Flood Outline ...... 45 Figure 5-4 Defences on the River Ure and Skell close to site R10 ...... 46 Figure 5-5 Current Flood Risk at Site R10 - Depth and Velocity ...... 48 Figure 5-6 Depth and Velocity of Flooding at site R10 for an undefended 0.1% AEP flood event ...... 49 Figure 5-7 Flood depth and velocities from the River Skell in a 0.1% AEP defended flood event ...... 51 Figure 5-8 Predicted depth of flooding at R10 site during River Skell 0.1% AEP undefended event ...... 52

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Figure 5-9 Comparison of latest 1 in 1000 year food outline with existing Flood Zone 2 ..... 53 Figure 5-10 Surface Water Flood Risk at site R10 ...... 55 Figure 6-1 - Site R32 Location and Topography ...... 59 Figure 6-2 1995 Observed Flood Outline ...... 60 Figure 6-3 Comparison of 1% flood event and 1% plus climate change event with Flood Zone 3 ...... 61 Figure 6-4 Comparison of Modelled 0.1% event with Flood Zone 2 ...... 61 Figure 6-5 Flood Depths in a Modelled 1% Flood Event ...... 62 Figure 6-6 Flood Depths in a Modelled 1% plus Climate Change Event ...... 63 Figure 6-7 Flood Depths in a Modelled 0.1% Flood Event ...... 63 Figure 6-8 200 Year Flood Map for Surface Water Flooding ...... 65 Figure 6-9 30 Year Flood Map for Surface Water Flooding ...... 65 Figure A1: SUDS Management Train Principle21 ...... I

List of Tables

Table 4-1 Flood Events in Masham (from EA Floodplain Mapping Study of Swinney Beck (2004) ...... 26 Table 4-2: Flood Hazard Rating ...... 33 Table 4-3 Maximum Hazard at Sites M1 and M3002 and on Key Access Routes ...... 34 Table 4-4 Average Hazard at Sites M1 and M3002 ...... 34 Table 4-5 Site M3002 Flood Risk Information ...... 36 Table 5-1 Predicted flood depths on site R10 for 1 in 1000 year event on the River Ure ..... 49 Table 5-2 Predicted flood depths on site R10 for 0.1%AEP event on the River Skell ...... 52 Table 6-1 Summary of Flood Depths (site R32) ...... 62 Table A1: Suitability of SUDS Techniques ...... II

Abbreviations

FRA ...... Flood Risk Assessment NPPF ...... National Planning Policy Framework NYCC...... North Yorkshire County Council PFRA ...... Preliminary Flood Risk Assessment SFRA ...... Strategic Flood Risk Assessment

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Definitions

1% AEP Flood Event ...... A flood event with a 1 in 100 probability of occurring in any year, (e.g. Flood Zone 3) 0.1% AEP Flood Event ... A flood event with a 1 in 1000 probability of occurring in any year (e.g. Flood Zone 2).

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1 Introduction

1.1 Background This Level 2 SFRA follows on from the North West Yorkshire SFRA (Volumes I, II) which formed the Level 1 SFRA. The purpose of this report is to provide a more detailed assessment of four areas of flood risk. These areas include site options for future housing and employment. The Level 2 SFRA will form part of the evidence base to help Council officers make recommendations to Members about the location of future development. The four areas are: • Pateley Bridge • Masham • Ripon - River Ure and River Skell • Ripon at Bishopton and are comprised of residential and employment site allocations. These sites were identified in the Level 1 SFRA as being at risk of flooding.

1.2 Scope and Objectives The Level 1 SFRA was formally published by Harrogate Borough Council (Harrogate BC) as part of the evidence base for the Harrogate District Local Plan in August 2010. The Level 2 assessment was commissioned in September 2011. This Level 2 SFRA provides more detail on four site options within Pateley Bridge, Masham and Ripon including recommendations for Flood Risk Assessments. The key objective of this study is to determine whether development of the site options would be safe. The Level 1 and 2 SFRAs for Harrogate BC have been prepared in accordance with current best practice as set out in the National planning Policy Framework and accompanying Technical guidance (DCLG, 2012). This document comprises the Level 2 assessment.

1.3 Study Area This study provides an assessment of flood risk in each of the four areas, where development/ regeneration conflicts with flood risk. This flood risk information will inform the preparation of the Harrogate District Sites and Policies DPD and include recommendations for Flood Risk Assessments. The Harrogate BC Level 1 SFRA has provided sufficient data and information to inform the application of the Sequential Test. This information was based on current available information, including: • Flood Zone maps • Modelled flood outlines • Flood risk management measures maps • Surface water flooding maps • Climate change maps North Yorkshire County Council has carried out a county wide exercise of prioritisation of surface water flood risk and interventions. This will underpin their draft Local Strategy which is currently being developed. This will outline their approach to management of flood risk in the county, including a prioritised programme and proposals for catchment studies and surface water management plans where appropriate. The Level 2 is focussing on the following four areas:

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1.3.1 Pateley Bridge Pateley Bridge is a market town located within the Nidderdale Area of Outstanding Natural Beauty (AONB). Pateley Bridge (including Bridgehousegate) is identified in the adopted Harrogate District Core Strategy as a Group B Settlement1 with a housing target of 3% of the total 390 new homes per annum up to 2023/242. Site P3001 is a being considered as a draft allocation for future housing and employment. The site is located to the east bank of the River Nidd, behind defences. The site comprises two sites that were considered separately as part of the Level 1 SFRA (P2 and P6). P2 is currently occupied by a highway depot and P6 a fuel merchants. The eastern part of the site is currently in Flood Zone 3. The Harrogate District Sites and Policies DPD Flood Risk Sequential Test concludes that although P3001 is affected by Flood Zones 2 and 3a, ‘it is a brownfield site and lies within the development limit. Whilst currently in employment use, in all other respects it meets the site selection methodology criteria. Before a decision can be made about whether or not this site can be allocated it will need to pass the Exception Test. This site (including access to the site) will be subject to a more detailed assessment as part of the Level 2 SFRA to establish whether it passes the Exceptions Test, and in particular to determine if development would be safe.’ Harrogate BC will also need to recommend how flood risk should be assessed for any development proposals. Since the completion of the Level 1 SFRA Harrogate BC have also collected information, which indicates that surface water flooding may be a significant part of the potential flooding issues at the site and these have been investigated in the Level 2 SFRA

Figure 1-1 Pateley Bridge Site Location and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue)

1 Policy SG2: Harrogate BC Core Strategy, adopted February 2009 2 Policy SG1: Harrogate BC Core Strategy, adopted February 2009 2011s5357 HBC Level 2 SFRA FINAL_August 2013 2

1.3.2 Masham Masham provides a service centre to the surrounding sparsely populated area and is a very important employment centre. Its setting attracts both day and overnight visitors. Masham is identified in the adopted Harrogate District Core Strategy as a Group B Settlement3 with a housing target of 2% of the total 390 new homes per annum up to 2023/244. Site M3002 is being considered as a draft allocation for future housing and employment. The site is located on the south bank of Swinney Beck. The site comprises two sites that were assessed separately in the level 1 SFRA (M6 and M1002). Site M6 is entirely in Flood Zones 2 and 3 and site M1002 has approximately one third in either Flood Zone 2 or Flood Zone 3. The Harrogate District Sites and Policies DPD Flood Risk Sequential Test concludes that although M3002 is affected by Flood Zones 2 and 3a, ‘it is well related to the existing settlement and in all other respects it meets the site selection methodology criteria. Before a decision can be made about whether or not this site can be allocated it will need to pass the Exception Test. This site (including access to the site) will be subject to a more detailed assessment as part of the Level 2 SFRA to establish whether it passes the Exceptions Test, and in particular to determine if development would be safe.’ The Level 2 SFRA also considers site M1 (Auction Mart) for comparison with other options in Masham. Harrogate BC will need to recommend how flood risk should be assessed for any development proposals.

Figure 1-2 Masham Potential Sites and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue)

1.3.3 Ripon - River Ure The City of Ripon is located 16km north of Harrogate and the city centre forms the main service and employment centre for extensive rural areas in the north of the district. Ripon is identified in the adopted Harrogate District Core Strategy as a Group A Settlement5 with a housing target of 8% of the total 390 new homes per annum up to 2023/246.

3 Policy SG2: Harrogate BC Core Strategy, adopted February 2009 4 Policy SG1: Harrogate BC Core Strategy, adopted February 2009 5 Policy SG2: Harrogate BC Core Strategy, adopted February 2009 6 Policy SG1: Harrogate BC Core Strategy, adopted February 2009 2011s5357 HBC Level 2 SFRA FINAL_August 2013 3

R10 is a being considered as a draft allocation for future housing and employment. The site is located south of the River Ure, behind recently constructed flood defences. The site is currently in Flood Zone 2, the flood zones were updated during the level 1 SFRA and at this stage it was removed from flood zone 3. Previous studies have identified a risk of flooding from deep water on parts of the site. In addition the Environment Agency has recently completed a flood defence scheme in Ripon. The Harrogate District Sites and Policies DPD Flood Risk Sequential Test concludes that although R10 is affected by Flood Zones 2, ‘a more detailed level 2 SFRA will need to be carried out before a decision is made to include it as an allocation in the publication draft of the sites and policies DPD.’ This will include any revisions to the flood zones following recent work associated with the development of the new Environment Agency flood defence scheme and identify whether the defences reduce flood risk at site R10. Harrogate BC will also need to recommend how flood risk should be assessed for any development proposals.

Figure 1-3 Ripon River Ure Site and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue)

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1.3.4 Ripon - Bishopton Site R32 at Bishopton (north Ripon) is on the River Skell. During the Level 1 SFRA the Flood Zones were revised and the site moved from Flood Zone 3 to Flood Zone 2. The Level 2 SFRA will establish the depth of flooding on the site, the impact of climate change and provide recommendations for developer Flood Risk Assessment. This information will enable Harrogate BC to compare the suitability of the site against other site options within Ripon.

Figure 1-4 Bishopton Site and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue)

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1.4 Outline Methodology As shown in Figure 1-1 to Figure 1-4 these sites are within Flood Zones 2 and 3. In Pateley Bridge and Ripon preferred sites could not be chosen in areas of lower flood risk (following Sequential Test) as they are key regeneration sites and required to help deliver Harrogate BC need for housing and employment in these principal and local centres. In Masham additional detail is required to support Harrogate BC decisions about preferred sites in the town. For sites which are in Flood Zone 3 the Exception Test will need to be passed if these sites are to be approved during examination of the Harrogate District Sites and Policies DPD. This will involve a more thorough study in order to truly understand the mechanisms of flood risk around these regeneration sites. A key objective of the Level 2 SFRA is therefore to inform the application of the Sequential Test, by assessing the development sites at medium and high flood risk, and assist Harrogate BC in establishing whether the requirements of the Exception Test can be met as outlined below:

a. It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared. If the LDD has reached the ‘submission’ stage (see Figure 4.1 of PPS12: Local Development Frameworks) the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal (SA); b. The development must be on developable previously-developed land or, if it is not on previously-developed land, that there are no reasonable alternative sites on developable previously-developed land; and c. A site-specific Flood Risk Assessment must demonstrate that the development will be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. Whilst the Exception Test process makes it possible to identify areas where developments can be built safely, it must not been seen as an opportunity to place inappropriate development in flood risk areas. It is a useful planning tool that can justify the acceptability of the residual risks remaining after the mitigation measures have been applied. In order to establish whether applying the Exception Test is justified or can then be satisfied, namely part c), the Level 2 SFRA considers the detailed nature of the flood hazard, taking account of the presence of flood risk management measures such as flood defences. The detailed nature of the flood hazard within a flood zones includes: • Flood probability; • Flood depth; • Flood Velocity; and • Rate of onset of flooding. These factors can be significantly affected by the presence of flood defences or any other infrastructure which acts as a flood defence. Flooding behind such infrastructure can occur either as a result of: • Constructional or operation failure of the defence, either in whole or in part (breach); or • Water levels rising to exceed the level of the defence (overtopping); or • Overloading of the surface water drainage system, either due to its own limited capacity, or being unable to discharge due to high water levels outside the defended area. By facilitating the application of the Exception Test, the Level 2 SFRA technical work will also provide supporting evidence to the possible mitigation measures that would enable the development to proceed.

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1.4.1 Pateley Bridge In Pateley Bridge the existing EA 1D HEC RAS hydraulic model of the River Nidd was extended to include a detailed representation of the floodplain including site P3001. This model was used to investigate flood flows across the floodplain, identify the role of defences in managing flood risk at the site and assess the existing risk. The site has also been identified as potentially being at risk of flooding from drainage and surface water flows. Local information has been collected from Harrogate BC, the EA, North Yorkshire County Council and Yorkshire Water to assess the risk in more detail than was possible in the Level 1 SFRA. No detailed drainage modelling has been carried out as this will be addressed as required by NYCC in their role as Lead Local Flood Authority (LLFA).

1.4.2 Masham In Masham the existing Environment Agency model was used to investigate the depth of flooding associated with the current flood zones. This provided additional local detail compared with the Level 1 SFRA and informed recommendations for development of the site. There was no new model development although this is recommended for the developer Flood Risk Assessment. The EA do not currently have any plans for flood zone improvement in Masham.

1.4.3 Ripon - Bishopton For the Bishopton site (R 32) the existing Environment Agency 1D ISIS hydraulic model of the River Skell was used to investigate the flood risk at the site in more detail including flood depth, climate change and potential downstream impacts of development. No new model development was carried out.

1.4.4 Ripon – Auction Mart (R10) Flood Risk from the River Ure and River Skell in Ripon at site (R10) was assessed using the revised Environment Agency ISIS model. This model was updated in spring 2012 to include the new flood defence scheme and provided for the SFRA in April 2013. This model was used by the EA to produce new flood outlines and these were used during development of this Level 2 SFRA. These were used in the assessment of flood risk including areas benefitting from defences, climate change and impact of development, at site R10.

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2 Flood Risk Review

2.1 River Nidd at Pateley Bridge

2.1.1 Previous Studies The existing flood zones (November 2011) were constructed from an Environment Agency (2009) 1D only (HEC-RAS) model of Pateley Bridge and these outlines place part of the P3001 allocation within Flood Zone 2 and / or 3 (see Figure 1-1). However, since these outlines were obtained by projection of channel levels across the local floodplain they do not take account of possible flow pathways across the floodplain. By contrast, 2D (or linked 1D­ 2D) hydraulic models are much better at simulating the kind of complex flow routes that can occur within urban areas and also have the benefit of routinely outputting high definition flood hazard (including depth and velocity) maps of the kind that are useful for SFRA Level 2 studies. Hence, to consolidate understanding of flood risk at the P3001 site, it was considered appropriate to add 2D representation of the floodplains to the existing 1D model. ISIS­ TUFLOW (linked 1D-2D) was the method of choice.

Flood Zone 3

Flood Zone 2

Figure 2-1 Site P3001 and the Environment Agency Flood Zones

The Environment Agency surface water flood map indicates that surface water flow from the higher ground to the north east of the site towards the lower ground at the junction of Greenwood Road/ Greenwood Avenue. Local anecdotal information also suggests that there is some backing up of the drainage network towards this same low point when river levels are high and outflow is restricted. Pateley Bridge is downstream of Gouthwaite Reservoir (a Yorkshire Water resource). The Environment Agency reservoir flood maps7 show that significant areas of Pateley Bridge including the site are in the flood outline associated with this reservoir. Flood risk from the

7 Available online at the Environment Agency website http://www.environment­ agency.gov.uk/homeandleisure/37793.aspx 2011s5357 HBC Level 2 SFRA FINAL_August 2013 8

reservoir has not been assessed for this study other than to note that these type of events are very rare. There are no canals in the area. North Yorkshire County Council (NYCC) has identified a prioritised list of sites for flood risk management plans. They are currently developing their proposals for investigations and interventions at these sites which will be outlined in their draft Local Strategy.

2.1.2 Site Visit A site visit was carried out in October 2011. This identified key structures, which could influence flood risk at site P3001, these are: • A single span footbridge upstream of the site although it should be noted that this has a wide arch with a high clearance above normal river levels • A weir just downstream of the site • Pateley Bridge just downstream of the site, the left hand arch (overspill) was blocked by scaffolding on the day of the site visit. This has been installed to support the footway and the timescale for resolving this is not known. These are shown in Figure 2-2 .

Footbridge Weir

Pateley Bridge Scaffolding

Figure 2-2 Structures Influencing Flood Risk at P3001

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The site visit also investigated the main elements of the flood defences in Pateley Bridge and found that they were typically in good condition. The condition reflects the recent work that has been carried out on the walls and embankments. Defences on the left bank close to the site are shown in Figure 2-3. The defences consist of a combination of earth embankments, stone walls and a flood gate that provides access onto the floodplain. In the earth embankment at the Sidings, in one location there was evidence of small animal burrows.

Lateral Embankment Embankment alongside “The Sidings”

Flood Gate

Figure 2-3 Pateley Bridge Flood Defences The information collected on the site visit was used to inform the development of the ISIS TUFLOW model and select appropriate scenarios for assessing risk at the site.

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2.2 Swinney Beck at Masham

2.2.1 Previous Studies The 2004 flood mapping study which underpins the existing flood zones (November 2011) used a combined HEC-RAS 1D river model and JFLOW (2D model) to model the spills from the watercourse and their flow routes through the village. The flood zones are a combination of output from the JFLOW model and extended HEC RAS water levels for areas downstream of site M3002 including the Auction Mart (site M1)8. There are no large reservoirs on Swinney Beck upstream of Masham and the Environment Agency risk from reservoirs maps2 do not identify Masham as at risk from reservoir flooding. There are no canals in the area.

2.2.2 Site Visit Swinney Beck at the location of Site M3002 is poorly maintained. On the date of the site visit the beck was heavily overgrown (see photo). The road bridge at Foxholme Lane (Swinney Beck Bridge) may be prone to blockage and overspill during flood events (see photo). The adjacent land is flat and overland flow routes could be in various directions. Spill flow paths potentially include the Site M3002 on the right bank of Swinney Beck since this site is currently at top of bank. Other spill routes may be north eastwards along Westholme Road. This may have been the flood route that caused historical flooding at the Auction Mart.

Roadbridge Watercourse

Figure 2-4 Structures Influencing Flood Risk at Site M3002 and Site M1

8 The Environment Agency, 2005. Swinney Beck, Dales Area Floodplain Mapping phase 2. JBA Consulting 2011s5357 HBC Level 2 SFRA FINAL_August 2013 11

2.3 Ripon - River Ure, River Laver and River Skell

2.3.1 Previous Studies The existing flood zones for the River Ure, River Laver and River Skell in Ripon are underpinned by EA modelling work carried out in 2004 using a 1D ISIS model for the river and Infoworks RS as part of the Feasibility study for the Ripon Flood Alleviation Scheme9. The model was revised in 200810 and new flood zones were issued by the EA in March 2009, these were used for the Level 1 SFRA analysis and have not been updated since 2009 (Figure 2-5). The 2009 update removed site R10 and parts of site R32 from Flood Zone 3 suggesting the extent of flooding on the sites may be sensitive to changes in the modelling work. Parts of both sites remain in Flood Zone 2. Flood Risk information provided by the Environment Agency for the Level 1 SFRA suggested that lower lying areas of site R10 may be at risk of deep flooding and that there may be a channel in the middle of the site that can act as a floodplain flow route during a flood event. The EA have revised their Ripon model which includes the River Ure, River Skell and River Laver (spring 2012)11 following the building of new flood defences on the River Ure. The existing model was a 1D ISIS model of the three watercourses; this has been updated to represent a new flood defence scheme on the River Ure at North Bridge. The model has also been extended to include a 2D Tuflow domain. This represents flow across the floodplain, including site R10 and allows flow routes, flood depths, velocities and hazard across the floodplain to be modelled. Site R10 is in this area and the updated model was used to look in more detail at the flood flow across the site. The EA have used this model to update their flood outlines and these will inform future Flood Zone improvements. The updated outlines were provided in April 2013 for use in this level 2 SFRA. These show a decrease in the proportion of the site flooded in a 0.1% AEP event (an event with a 1 in 1000 chance of occurring in any year) with flooding focussed in a channel across the middle of the site. Flood outlines have also been provided for a scenario including future climate change. These revisions do not change the Flood Zones on the River Skell at site R32.

R16

R3

R32

R1002

R36

Figure 2-5 Bishopton Site and Flood Risk (EA Flood Zones - FZ3 dark blue and FZ 2 light blue)

9 The Environment Agency, 2004. Ripon Flood Alleviation Scheme Modelling Study, Halcrow. 10 The Environment Agency, 2008. Data improvements and update of 2004 study 11 Updated model outlines provided by the EA in April 2013. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 12

2.3.2 Site Visit - River Ure (Site R10) On the date of the site visit the new defences on the River Ure had been recently completed. The defence works were in good condition. The defences benefit Site R10 which prevent spilling over the right bank of the River Ure and river flooding upstream of the site for river flows and levels up to the design event. North Bridge is a multi-arch bridge over the River Ure which is close to the site. The structure has an impact on river flood levels in the site locality. The in-channel bridge arches take the normal river flow. Flood relief arches to the right and left of main channel provide additional flood capacity. It was noted that there is a tree partially blocking the left hand flood relief arch of the bridge which will limit the flow at this point. It was also noted that the flood relief of the right hand flood relief arches have been improved with the recent defence works.

2.3.3 Site Visit - River Laver and River Skell (Site R32) The River Laver joins the River Skell on the west side of Ripon. Site R32 is next to the River Laver west of Ripon town centre. Site R32 generally slopes from north to south. The northern and eastern part of the site is on higher ground. Observations of the site and river channel suggest that this part of the site is unlikely to flood from the River Laver. The southern and western part of the site is at higher risk of flooding owing to its proximity to the river and lower level. There are localised depressions within the boundary of the site that could collect surface water runoff during extreme flood events. The River Laver adjacent to the site has very poor channel capacity generally. The channel is heavily wooded with tree growth along both banks. A tree obstruction which caused an abrupt river meander in the main channel was observed downstream of High Dam which is an in- channel structure alongside the site. This will have an impact on river levels in flood events which would impact the south-western part of the site. Development on higher ground to the north of the site will need to be considered for potential surface water flood risk from the existing development.

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3 Pateley Bridge

3.1 Introduction Site P3001 is located on the east bank of the River Nidd in Pateley Bridge. Parts of the site are in the Environment Agency Flood Zones 2 and 3 as are potential access routes. The Sidings, Millfield Street and Little King St are in Flood Zone 3 and Greenwood Road is in Flood Zone 2. The Flood Zones represent the perceived undefended risk at the site and the actual risk will be influenced by the raised defences between the River Ure and the site. There is also an area of higher ground to the north of the site. As discussed in Section 2.1.1 the EA flood zones are based on a model of the River Nidd with flood levels projected across the flood plain. These do not take account of potentially complex flow routes in the urban area. For the Level 2 SFRA an ISIS - TUFLOW model was developed to improve the representation of the flood plain and better model the impact of flood flows around the site. The revised model was therefore used to obtain a more detailed assessment of actual flood risk at the site including the role of defences and the consequences of breach or failure of defences. Since the Level 1 SFRA was carried out in 2010, Harrogate Borough Council have obtained additional anecdotal information about surface water flooding. The Environment Agency Surface Water maps have been revised since the Level 1 SFRA was carried out and these will be used in combination with anecdotal evidence and information about drainage were used to assess the role of surface water flooding in the overall flood risk at the site.

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3.2 Existing Risk - River Flooding

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

1% AEP 1% AEP plus Climate Change

0.1% AEP Extreme Flood

Figure 3-1 Existing Risk in Pateley Bridge

The existing risk at the site was modelled including the defences on both banks of the River Nidd. This indicates that the site and its access routes would remain dry during a 1% AEP event (and a 1% AEP event including climate change). In an extreme 0.1% AEP event there would be shallow (<0.40 metres) flooding on the site arising from floodwater overtopping the embankment just upstream of the weir. These are shown in Figure 3-1 below. Note that the floodwater does not overtop the higher ground to the north of the site in any of these scenarios but does reach the base of the embankment (along the line marked 'path') in the 1% AEP plus climate change and 0.1% AEP events. Summary • Shallow flooding on site P3001 in extreme 0.1% AEP event, some flooding on fringes of the site in a 1% AEP plus climate change event. • Route of floodwater onto site is by direct overtopping of flood defence embankment adjacent to the site. • Access to the site may be hampered by ponded flood water up to 0.50 metres deep along parts of Millfield St and the Sidings during the 0.1% AEP extreme flood event.

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3.3 Role of Defences - River Flooding

3.3.1 Undefended Scenario The model was also run with the defences removed. The results (in Figure 3-2) can be compared with the existing risk scenario shown in Figure 3-1 to assess the impact of the defences on flood risk at site P3001. This shows the apparent paradoxical situation that the undefended flood risk to the P3001 site is lower than the existing (defended) risk to the site. The reason for this is that removing all defences from Pateley Bridge enables flood water to flow relatively unhindered through the caravan park along the right bank of the River Nidd. This lowers water levels in the Nidd to the extent that they do not reach the natural level of the left bank. A greater risk to the site would be if there was failure of the left bank only and this situation has been partly assessed with the breach model.

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

1% AEP 1% AEP plus Climate Change

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

0.1% AEP Extreme Flood

Figure 3-2 - Modelled Undefended Flood Depth Maps

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3.3.2 Breach of Defences A breach location was chosen adjacent to site P3001. This scenario models a 40m gap in the embankment. In practice the condition of the embankment is good and the likelihood of this scenario is low. Figure 3-3 shows the embankment in this area.

Embankment near chosen Breach location

Figure 3-3 Embankment near modelled breach location The results of the breach models are shown in Figure 3-4. This demonstrates that the P3001 site would be at risk from local failure of the left bank adjacent to the site during all of the modelled return periods. Flood depths at the site would be variable owing to the variable ground levels but would reach a maximum of around 1.0 metre during a 1% AEP (present day) event and 1.5 metres during both 1% with climate change and 0.1 AEP (present day) events. After initial flooding of the site peak velocities are typically low (<0.1m/s) across most of the site. Locally higher velocities (up to 0.3 m/s) are modelled round the edge of the site where water spill in and along a flow route through the site towards Greenwood Road during the 1% AEP climate change and the 0.1% AEP flood events. It should, however, be noted that overtopping of the existing embankment crest does not occur during a 1% AEP event so the risk of a breach occurring during this magnitude of event should be considered to be low. Similarly, since the embankment was assessed to be in good condition as part of an asset inspection that was carried out for this study, the risk of a breach occurring during both 1% with climate change and 0.1% AEP events should also be considered to be low.

2011s5357 HBC Level 2 SFRA FINAL_August 2013 17

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

1% AEP 1% AEP plus Climate Change

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

0.1% AEP Extreme Flood

Figure 3-4 Modelled Local Breach Flood Depth Maps

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3.3.3 Flood Gate Failure Figure 3-5 shows the results of the model runs simulating failure of the flood gate just upstream of Pateley Bridge. These demonstrate that there would be no increased risk to the P3001 site from failure of the flood gate. Failure of the flood gate is modelled to lead to a highly localised increase in flood depth in the region between Mill Lane and the existing position of the flood embankment on the left bank.

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

Floodgate

1% AEP 1% AEP plus Climate Change

Flood Depth (metres) >2.00 1.00-2.00 0.75-1.00 0.50-0.75 0.25-0.50 0.00-0.25

Floodgate

0.1% AEP Extreme Flood

Figure 3-5 Failure of Floodgate

3.3.4 Summary The flood defences in Pateley Bridge raise the bank levels on both sides of the river and retain floodwater in the river channel. In the absence of the current defences water would preferentially flow out of the channel along the lower right bank of the river and through the caravan site. In the event of a local breach of the defence embankment adjacent to the site, there could be flooding of up to 1.0m depth in a 1% AEP event. However, since the defences are currently considered to be in a good condition, the risk of a local breach is considered to be low. A potential failure of the flood gate (Figure 2-3) located as shown in Figure 3-5, leads to an increase in local risk in the Mill Lane area but does not directly affect site P3001.

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3.4 Impact of Development The impact of development on flood risk from the river has not been modelled as there is little flooding on the site in the 1% AEP event.

3.5 Climate Change Impacts Figure 3-1 to Figure 3-5 compare the 1% AEP event with the 1% AEP plus climate change allowance. In the existing risk and the failure of flood gates scenario the future 1% AEP event shows a small increase in flood extent on the western edge of site P3001 and along the access routes of The Sidings and Millfield St. In the breach scenario there is an increase in the depth of flooding from around 1.0.5m to 1.5m. This indicates that in the future there will be a small increase in risk associated with climate change. The most significant increase in risk is associated with the breach scenario and, as discussed in section 3.3.2 the probability of this scenario is low.

3.6 Surface Water Drainage and Flood Risk North Yorkshire County Council (NYCC) note that the drainage system in Pateley Bridge has surcharged in two locations (Top Wath Road and Nidd Walk) in past flood events in the town on the north (left) bank of the River Nidd. These locations are downstream of the proposed redevelopment sites. In other locations the fire and rescue services database has other known locations of call outs to problems but with no detailed information available. Overall, problems seem to be distributed in Pateley Bridge rather than concentrated at one or two locations. The records of past events are shown on Figure 3-6. There is anecdotal evidence from local landowners of poor surface water drainage at the northern end of Greenwood Road at the boundary of Site P3001. The poor drainage occurs when river levels are high. There is also anecdotal evidence of runoff from the higher agricultural land to the north which drains to this location. The surface water flood map shows potential risk for the 30 year and 200 year extreme rainfall events. The land rises steeply to the northeast of the redevelopment sites and although historical information is limited the topography suggests that the site may be prone to surface water flooding. This could be the case in extreme events when the drainage system is unlikely to be able to take all the runoff. The predicted flooding from the surface water flood map for the 30 year storm event is also shown on Figure 3-6. There are no sewer DG5 records for Pateley Bridge. However, owing to the steep topography surface water will drain to the River Nidd. When river levels are high the lower parts of the sewerage are likely to surcharge. This may include Millfield Street close to the development sites.

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Figure 3-6 Pateley Bridge Surface Water Flood Map and historical records

3.7 Exception Test Summary The Exception Test must be applied if the sequential testing process cannot identify enough sites where flood risk is low. Harrogate Borough Council have produced the Harrogate District Site and Policies DPD Flood Risk Sequential Test summarising their Sequential Testing process. This has identified some sites where the Exception Test will be required and several others where, although the Exception Test may not be required there is uncertainty about whether development can be made safe. The Exception Test has three requirements: Part A - It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared. If the LDD has reached the ‘submission’ stage (see National Planning Policy Framework and associated Technical Guidance) the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal (SA); Part B - The development must be on developable previously-developed land or, if it is not on previously-developed land, that there are no reasonable alternative sites on developable previously-developed land; and Part C - A site-specific Flood Risk Assessment must demonstrate that the development will be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. Part A will be demonstrated by Harrogate BC based on their development needs identified in their Core Strategy12. Part of site P3001 is used as a Fuel Merchant and the remainder has been used by NYCC as a Highways depot (now closed) and it therefore 'previously developed' land and will pass Part B of the Exception Test.

12 Harrogate Borough Council, Core Strategy, Adopted February 2009. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 21

A full Flood Risk Assessment for a specific development proposal is required to pass Part C of the Exception Test and the information in this Level 2 SFRA can only be used to indicate whether it is likely that the site will pass. In the case of site P3001 in Pateley Bridge this SFRA has used 2D modelling to investigate flood plain flow and the role of defences and found that: • There is no flooding on the site in the 1% AEP flood event due to flood defences. • There is shallow flooding in the 0.1% AEP event (<0.4m) as the defences are overtopped just upstream of the weir. Access to the site may be hampered by ponded water (up to 0.5m deep) along Millfield St and the Sidings. • The defences in Pateley Bridge raise river banks on both sides of the river. In the absence of the defences water would preferentially flow out of the channel on the right (west) bank. The failure of the flood gate upstream of the site does not increase the modelled risk at site P3001. If defences were breached adjacent to the site then there is a risk the flood depths could reach 1m in some parts of the site in a 1% event and up to 1.5m in a 0.1% event. After the initial flooding, velocities across the site would be fairly low. • The defences are currently in good condition and the risk of breach is low as the defences are not overtopped in a 1% event. The condition of the defences is currently good suggesting that the risk of breach in the climate change and 0.1% events is also low. • Climate change modelling finds a small increase in risk, particularly in the breach scenario. However the risk of this scenario is low. • The site and surrounding areas have a history of flooding from surface water due to the local topography. • Some access routes to the site are subject to flooding in 1% and 0.1% events and a route which is passable during flood event should be chosen. The impact of development was not modelled in detail as there is no flooding of the site during a 1% event due to the flood defences. This suggests that it is likely that development on this site could be made safe and would pass part C of the Exception Test. The Level 2 SFRA has indicated that the risk of flooding from the river is low due to the defences which are currently in good condition. There would be flooding of the site if the defences were breached but the probability of this is low. The defences are overtopped in a 0.1% event leading to shallow flooding on the site. There is a risk of surface water flooding and the developer must demonstrate that this has been addressed in their Flood Risk Assessment. The access to the site should avoid roads at risk of flooding. The developer must now demonstrate that their site specific proposal has addressed the risks and can pass part C of the Exception Test. This includes reducing flood risk elsewhere which on this site could potentially include surface water drainage improvements. Detailed recommendations for Flood Risk Assessments and site developments are provided in the following sections.

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3.8 Recommendations for the Preparation of Flood Risk Assessments This section presents recommendations for site specific flood risk assessments. The LPA and Environment Agency should be consulted in order to scope the content and level of the FRA. The SFRA has assessed flood risk at a strategic level, which can be used to provide baseline evidence for a FRA. However, where a more detailed FRA is required the developer should undertake a detailed assessment of the flood risk to the site, using the SFRA to scope out flood risk issues, the National Planning Policy Framework and its accompanying Technical Guidance (DCLG 2012). Developers should satisfy themselves that the data provided in the SFRA is up-to-date and accurate for their development. Site P3001 in Pateley Bridge currently has light industrial use and part of the site is used for coal storage. The FRA should consider past use of the site, particularly in relation to the suitability for SUDs and surface water infiltration.

3.8.1 Breach of defences The risk is considered to be low. Any breach is likely to result in slow inundation because the embankments are low in height and the crest levels are high compared to the normal river levels. Nevertheless, in the event that defences do fail under extreme flood conditions, the FRA should consider whether emergency evacuation from the area is necessary. It should also address whether emergency escape routes are necessary and whether some routes could be cut off by ponding water in the Millfield Street area. The FRA should consider the condition of the defences and there should be some record of the maintenance regime on the river defences.

3.8.2 Surface water flooding Surface water flooding from land at a higher elevation, particularly to the northeast of the site should be considered. The local drainage paths of surface water and locations and potential depths of ponding water will need to be considered to ensure that they do not impact the proposed development. This will require a detailed consideration of the proposed site levels, the surrounding topography and the potential volumes of runoff against the capacity of the existing drainage network. The surface water flood map suggests that the proposed Site P3001 may be susceptible to surface water flooding. Greenwood Road, close to the site, currently seems to suffer from poor drainage when river levels are high and the surface water sewerage surcharges. This issue will need to be addressed in the FRA.

3.8.3 Site drainage An investigation of sewer capacity is advised which should include discussions with Yorkshire Water about the proposed discharge from the new development. Harrogate BC drainage engineer13 has commented that the existing system seems to be prone to surcharge under extreme storm events. The new development must consider the impact of development on the existing infrastructure and development. The Environment Agency has recommendations for reducing the impacts of surface water runoff and discharge from new development. Development Site P3001 is likely to be treated as a brownfield site in view of the existing light industrial activity on the current site. SUDs The Environment Agency is keen to promote the use of Sustainable Urban Drainage systems (SUDs) and draws attention to the National Planning Policy Framework and its accompanying technical guidance. SUDs tackle surface water run-off problems at source using features such as soakaways, permeable pavements, grassed swales, infiltration trenches, ponds and

13 Mike Wickens, Harrogate BC, consulted December 2011 2011s5357 HBC Level 2 SFRA FINAL_August 2013 23

wetlands, and, green roofs to attenuate flood peak flows, produce water quality improvements and environmental enhancements. The Environment Agency seeks to promote the use of SUDs techniques to this site and expect the developer of the site to submit detailed investigations such that the use of SUDs has been fully explored. The suitability of SUDs will need to be assessed for Site P3001 particularly in view of the low lying location of the site at the foot of the hillside to the east. Groundwater levels may be high during flood conditions. Further information about SUDs and Drainage is provided in Appendix A. Brownfield sites There must be no increase in surface water runoff from the site. As a consequence of climate change and recommendations in the Pitt Review the Environment Agency would want to see as a minimum a 30% reduction in surface water discharge, for any new development, from the site. Further consideration should be given to further regulating the discharge to the greenfield run-off from a 1 in 1 year storm (approximately 1.4 l/s/ha) and sufficient storage to accommodate a 1 in 30 year storm as a minimum. The design should also ensure that storm water resulting from a 1 in 100 year event, plus 30% typically to account for climate change, and surcharging the drainage system can be stored on the site without risk to people or property and without overflowing into the watercourse. On site long term stormwater storage Long term storage is required to mitigate the effects of additional volume of surface water runoff that a developed site will generate. The need for it is most easily identified by calculating the difference between the runoff volumes for the greenfield versus developed site in a 6 hour, 100 year event (as per Interim Code of practice for SUDs). However, comparisons should also be carried out over a time series of storm events to determine the critical volume required. The magnitude of this volume will be influenced by the site soil type, in itself a parameter which determines greenfield runoff volume. It is intended that additional volume that spills from the attenuation storage is held in an area which drains very slowly – i.e. the long-term storage. To achieve the necessary slow drain down, infiltration is needed. If this cannot be achieved with the use of SUDs systems, then a maximum discharge of 2 litres/sec/ha will be allowed into the drainage system. However, this figure will need to be agreed with Yorkshire Water plc.

3.8.4 Flood Risk from Reservoirs Gouthwaite Reservoir (YWS) impounds the River Nidd upstream of Pateley Bridge. Following the recommendations of the Pitt Review, DEFRA and the Environment Agency have prepared inundation maps (at various levels of detail) of all reservoirs falling within the remit of the Reservoirs Act 1975, which includes Gouthwaite. These inundation maps show the effects of a dam breach on the downstream area and are available on the Environment Agency website. The flood outline for Gouthwaite Reservoir is a corridor approximately 400m wide and includes parts of Pateley Bridge including site P3001. It should be noted that in the UK dam breach events are very rare and the risk from Gouthwaite reservoir has not been investigated any further in this SFRA. In this case the site is part of a broader emergency planning scenario for Pateley Bridge and any future development should be added to existing warning arrangements.

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3.9 Development Recommendations

3.9.1 Site Layout It is recommended that development avoids the western side of the site as future flood risk increases in that area. If this is not possible then ground / floor levels should be sufficient to cope with the modelled climate change flood event. It should be noted that the extreme (0.1% AEP event is only 10% greater flow than climate change developing to be safe in 0.1% AEP event should be considered. The greatest flood risk on the site is for the local breach scenario (Figure 3-4) and raising of flood levels above this would reduce flood risk to the development.

3.9.2 Emergency Planning There is some flooding on access roads to the site (particularly The Sidings, Millfield Street and Little King St which are in Flood Zone 3 and Greenwood Road which are in Flood Zone 2). An access route to the site which is passable in all events should be chosen to allow evacuation and/ or access for emergency services.

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4 Masham

4.1 Introduction Masham has a history of flooding from Swinney Beck. Known flood events are shown in the following table, from the Environment Agency study of flooding from Swinney Beck14 for Flood Zone development. Table 4-1 Flood Events in Masham (from EA Floodplain Mapping Study of Swinney Beck (2004)

Previous studies have identified several overland flood pathways through the village from Swinney Beck. In particular Westholme Road and/or Fearby Road with the Fearby Road route identified in Table 4-1 as contributing to the flood events on the Auction Mart Site (M1) in 1976 and 2000. Following the sequential testing of potential sites in Masham sites M1 was not a preferred option due to flood risk identified in the Level 1 SFRA (Site M3002 was assessed as two sites M6 and M1002). However, site M3002 is affected by Flood Zones 2 and 3a. The site is well related to the existing settlement and in all other respects it meets the site selection methodology criteria. Before a decision can be made about whether or not this site can be allocated it will need to pass the Exception Test. This site will be subject to a more detailed assessment as part of the Level 2 SFRA.

14 Dales Area Floodplain Mapping Phase 2 Studies – Swinney Beck, JBA Consulting for the Environment Agency, 2004 2011s5357 HBC Level 2 SFRA FINAL_August 2013 26

This Level 2 SFRA is using existing models and data to provide additional evidence to support this decision. Further detailed modelling is recommended for any Flood Risk Assessment but this study adds site specific detail to the information provided in the Level 1 SFRA in a way that is proportionate to the council's decision. The sites are shown below.

Figure 4-1 Sites M1 and M3002 in Masham The 2004 flood mapping study which underpins the flood zones used a combined HEC-RAS 1D river model and JFLOW (2D model) to model the spills from the watercourse and their flow routes through the village. The flood zones are a combination of output from the JFLOW model and extended HEC RAS water levels for areas downstream of site M3002. The flood zone outlines for site M1 are based on the extended HECRAS sections although the JFLOW model does indicate flooding on the site. The flood history of the village indicates that the JFLOW model may be underestimating risk. For this study the use of an alternative model (JFLOW+) was investigated as was the use of more recent LIDAR data for topography. This model confirmed the known flow paths through the village with flooding on the Auction Mart (M1) via a flow route down Fearby Road. There was increased depth of flooding on the fields to the north of Fearby Road (but no greater extent). The model did not predict flooding on site M3002 however the main channel spills are upstream at Swinney Beck High Bridge rather than at Swinney Beck Bridge. The extent of modelled flooding is sensitive to the floodplain topography used in the model; Westholme Road adjacent to the site is at a similar level. The road is flat and careful survey is required to determine whether water leaving the channel at Swinney Beck Bridge would flow down towards Fearby Road (increasing risk at the Auction Mary site) or along Westholme Road and/ or onto site M3002. There are too many uncertainties to determine whether the outlines were more accurate than those produced in the 2004 study. The inflow points for the original model were chosen at low points in the Swinney Beck embankments but there may be other spills that are not included. A more detailed review of flood risk would involve a 1D-2D linked model such as ISIS-TUFLOW, overtopping locations would be predicted by the model and linked to flow routes through the village. Topographic survey to identify flow routes and confirm the accuracy of the LIDAR data would also be required. This is a recommendation for the Flood Risk Assessment as it would involve substantial new modelling and topographic survey work.

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The Environment Agency have confirmed that they have no plans to review or revise the Flood Zones in Masham and therefore the existing JFLOW model (including the hydrology) that was used to develop the flood zones was used to investigate flood risk at sites M1 and M3002.

4.2 Existing Risk

4.2.1 Extent of Flooding The flood zones for Masham are shown in Figure 4-2, and the JFLOW outlines produced for the Environment Agency in the 2004 mapping study are shown in Figure 4-2. Both figures show all or part of site M1 at risk of flooding and part of site M3002. Figure 4-3 shows the flood routes down Westholme and Fearby Roads. The flood history (Table 4-1) for Masham indicates that the Auction Mart site (M1) formed part of the flood route from Swinney Beck to the River Ure. In 1976 and 2000 flood water flowed down Fearby Road and into the Auction Mart and most of this route is captured in the JFLOW modelling (Figure 4-3) the water ponds west of the Leyburn Road and enters the Auction Mart from the north. This suggests that the modelling may underestimate the flow from Swinney Beck upstream of Swinney Beck High Bridge and therefore the flow down Fearby Road. It is not known whether blockage or other channel restriction contributed to all of the historic flood events at the Auction Mart site but it has been mentioned as a contributing factor in some cases. It should be noted that the flood zones do not take account of channel or structure blockages and under these circumstances the flood risk would be higher.

Figure 4-2 Masham Flood Zones

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Fearby Road

Existing Building

Figure 4-3 Masham 2004 JFLOW outlines

4.2.2 Depth of Flooding Figure 4-4 shows the peak depth of flooding from the JFLOW model. In a 1% AEP flood event peak depths at site M1 are between 0.5 and 1 m. At site M3002 peak depths are typically lower (<0.5m) with a small area > 1 m. In a 0.1% AEP event flood depths are greater with both sites showing significant areas greater than 1m, although overall depths are lower (0.5 ­ 1m) at site M3002. An area of deeper flooding can be seen at the junction of Foxholme Lane and Westholme Road (close to the bridge over Swinney Beck) and along Westholme Road and this may restrict access to site M3002 during flood events.

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1% AEP Flood Event

0.1% AEP Flood Event

Figure 4-4 Peak Depth of Flooding (JFLOW)

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Summary • Auction Mart (site M1) - flood depths greater than 1m are predicted on this site in both the 1% and 0.1% AEP events. • Westholme Road (Site M3002) - flood depths in a 1% AEP event are typically below 0.3m, however in a 0.1% AEP flood event there is a significant increase in depth to 0.5 - 1m. • Deeper flooding is seen at the junction of Foxholme Lane and Westholme Road and along Westholme Road and this may restrict access to site M3002 during a flood event.

4.2.3 Velocity of Floodwater Figure 4-5 shows the velocity of floodwater at both sites for a 1 % AEP flood event (equivalent to flood zone 3) and a 0.1% AEP event (equivalent to flood zone 2). High velocity flood waters are dangerous even when depths are relatively shallow. Figure 4-6 categorises hazard from combinations of flood depth and velocity using output from a DEFRA/ Environment Agency R+D project. This shows that in a 1% AEP flood event velocities at site M1 are typically 1- 1.5 m/s increasing to greater than 2m/s in a 0.1% AEP event. The flood history at the site indicates that at least part of the site is on the flood route between Swinney Beck and the River Nidd (via Fearby Road) and in these cases flood water flowed across the site towards the north rather than ponding. This means velocities are likely to be high. At site M3002 velocities are typically less than 0.3 m/s in a 1% AEP event with a big increase to > 2m/s in a 0.1% AEP event. The model also shows areas of higher velocity flood water down Westholme Road, Fearby Road and on the A5108 all of which may make access difficult during a flood event.

1% AEP Flood Event

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0.1% AEP Flood Event

Figure 4-5 Flood Velocities (JFLOW)

Summary • Auction Mart (site M1) - in a 1% AEP flood event velocities at site M1 are typically 1­ 1.5 m/s increasing to greater than 2m/s in a 0.1% AEP event. • Westholme Road/ Foxholme Lane (site M3002) - velocities are typically less than 0.3 m/s in a 1% AEP event with big increase to > 2m/s in a 0.1% AEP event • The velocity of flood water on roads adjacent to site M3002 (Westholme Road and Foxholme Lane) may restrict access during a flood event.

4.2.4 Flood Hazard Flood Hazard is a combination of flood depth and velocity. Depths below 0.25m and velocities below 0.5m/s are considered to be low hazard. The Hazard can be categorised as shown in Figure 4-6 below. This gives a hazard category. The lower categories indicate hazard for more vulnerable groups and the highest of these ('Danger to all') includes emergency services.

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Figure 4-6: Danger to People from Depth and Velocity (table 13.1 from FD 2320 Flood Risk Assessment Guidance for New Development Phase 2 Defra/EA Flood & Coastal Defence R&D Programme TR2 (Technical Report 2), October 2005)15

Table 4-2: Flood Hazard Rating Flood Hazard Rating Hazard to People 0 No Hazard 0 to 0.75 Very low hazard 0.75 to 1.25 Dangerous for some - includes children the elderly and the infirm 1.25 to 2.0 Dangerous for most - includes general public Over 2.0 Dangerous for all - includes emergency services

The maximum hazard category has been estimated for each site and their main access routes using the matrix in Figure 4-6. These are shown in the table below.

15 table 13.1 from FD 2320 Flood Risk Assessment Guidance for New Development Phase 2 Defra/EA Flood & Coastal Defence R&D Programme TR2 (Technical Report 2), October 2005) 2011s5357 HBC Level 2 SFRA FINAL_August 2013 33

Table 4-3 Maximum Hazard at Sites M1 and M3002 and on Key Access Routes

Site Flood Event Maximum Maximum Hazard Flood Depth Flood Velocity Category (m) (m/s) M1 1% AEP (Flood 0.8 2.89 Danger for all Zone 3) 0.1% AEP 1.87 7.82 Danger for all (Flood Zone 2) M3002 1% AEP (Flood 1.14 2.16 Danger for all Zone 3) 0.1% AEP 1.81 5.07 Danger for all (Flood Zone 2) Westholme Road 1% AEP (Flood 0.77 1.82 Danger for all Zone 3) 0.1% AEP 1.54 4.27 Danger for all (Flood Zone 2) Fearby Road 1% AEP (Flood 0.71 1.47 Danger for most Zone 3) 0.1% AEP 1.45 2.57 Danger for all (Flood Zone 2) Foxholme Lane 1% AEP (Flood 0.54 2.15 Danger for all Zone 3) 0.1% AEP 1.25 2.52 Danger for all (Flood Zone 2) A6108 (Leyburn 1% AEP (Flood 1.12 3.37 Danger for all Rd Road) Zone 3) 0.1% AEP 1.69 4.33 Danger for all (Flood Zone 2)

Table 4-4 Average Hazard at Sites M1 and M3002 Site Flood Event Mean Flood Mean Flood Hazard Rating Depth (m) Velocity (m/s) based on mean values M1 1% AEP (Flood 0.31 0.83 Danger for most Zone 3) 0.1% AEP 0.92 2.36 Danger for all (Flood Zone 2) M3002 1% AEP (Flood 0.2 0.53 Very low hazard Zone 3) 0.1% AEP 0.61 1.27 Danger for most (Flood Zone 2)

Summary • The maximum hazard on parts of the Auction Mart site (M1) and site M3002 is high (Danger to All). Using the mean depth and velocity for each site finds that the Hazard at site M1 (Auction Mart) reduces slightly to 'Danger for Most' in a 1% event. At site M3002 the average flood depth and velocity is relatively low in a 1% event and the average hazard is low in this event. Note that in some of the historic flood events the Auction Mart site (M1) has been identified as part of the flow route from Swinney Beck to the River Ure.

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• Parts of the main access routes to site M3002 are predicted to be blocked with deep fast flowing water categorised as 'Hazard to All'. This would make access difficult during a flood event.

4.3 Impact of Development on Flood Risk

4.3.1 Compensatory Storage Development on sites at risk of flooding takes up space in the flood plain and displaces flood water. The Environment Agency requires compensatory storage to be provided to accommodate this displaced floodwater for developments in Flood Zone 3. This would be required for any development at the Auction Mart Site (M1) and could be required for development on site M3002 (depending on the final site layout).

4.3.2 Alternative Flood Flow paths Displaced floodwater must find an alternative route. Site M1 (Auction Mart) slopes to the north and is seems likely that any displaced flood water would increase flooding on the allotments to the north of the site. This is the observed route of historic flood flow. There is also a risk that floodwater reaching the junction of Fearby Road and the A6108 could combine with floodwater flowing down Westholme Crescent and increase flood risk to properties on Fearby Road if the flow route through the Auction Mart was blocked. Site M3002 is fairly flat and there is a risk that displaced flow water could flow towards the back of properties on The Oaks. Swinney Beck also floods downstream of the site and any displaced floodwater must not increase this risk.

4.4 Updated Level 1 Table for Site M3002 Site M3002 on the western edge of Masham near Swinney Beck Bridge was considered as two separate sites in the Level 1 SFRA. For the Level 2 SFRA, it has been considered as one site and a new flood risk information table has been developed for it (Table 4-5).

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Table 4-5 Site M3002 Flood Risk Information Masham Site M3002 Land Use Field Area (Ha) 2.66 % of site in FZ 1 37.97 % of site in FZ 2 44.36 % of site in FZ 3a 17.67 % of site in FZ 3b 0 % of site at risk of flooding (in FZ 2 62.03 or 3) Total % of site vulnerable to surface 6.77 water flooding Source of watercourse flooding Swinney Beck Other sources of flooding? Surface water – Figure 2 -1 shows that surface water flooding is minimal to the site and the main area shown to be flooded coincides with FZ 3 area. FZ 3 area requiring compensation 0.47 flood storage (Ha) SEQUENTIAL TEST SFRA recommendation Allocate - subject to appropriate access plans. (allocate/avoid) EXCEPTION TEST Defended Part of site in existing flood warning area, no defences Greenfield Yes Access during flood event Parts of Foxholme Lane and Westholme Road to the north of the site are flooded. Access is a key issue.

The maximum depths and velocities predicted by the JFLOW model on the access roads are given in Table 4-3 Maximum Hazard at Sites M1 and M3002 and on Key Access Routes

Flooding during the 1 in 100 year event covers only a small part of Foxholme Lane but it is directly adjacent to the site. Just to the west of the site, Foxholme Lane is not flooded but to provide access from here would involve developing outside of the currently designated potential site. Model available Yes Comment • Exception test required for housing development in FZ 3a (17.67% of site). • Housing in FZ 2 (44.36% of site) does not need exception test. • The design of any development on the site should concentrate built up areas in FZ1 on the

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Masham Site M3002 south of the site and avoid development in the small part of the site in FZ3. • Access to the site (potentially from Foxholme Lane) would have to be included in the development as there is currently no access from Westholme Road • Depth of flooding in 1 in 100 year event <0.8m, mainly less than 0.5m on access roads. Some flooding to Foxholme Lane near to junction with Westholme Road but depths mostly <0.5m in 1 in 100 year event. • 1 in 100 year depth of flooding on site up to 1.14m • 1 in 1000 year depth of flooding on site up to 1.81m • Highest depths predicted on site are adjacent to Westholme Road, development of this area should be avoided. Recommendation for Development • Adjust site boundary and/or design layout to avoid areas of flood risk (mainly north eastern corner of site). Include flood risk areas as open space. Particularly avoid developing in FZ 3. Development in FZ 2 could be minimised. • Small area of site, which coincides with area of site in FZ3 is at risk of surface water flooding and this should be considered during site design. • Consider access to site during flood events at site design stage. This may involve a new access route to the site from Foxholme Lane, Westholme Road is shown to flood in the 1 in 100 year event.

A significant proportion of site M3002 is in Flood Zone 1 and could be developed; the small north eastern part of the site in FZ 3 should not be developed and should be left as open space as part of the design. A larger part of the site is in FZ 2 and flood depths on the site during the 1 in 1000 year flood event are up to 1.81m based upon the JFLOW modelling work undertaken in 2004 by JBA. Velocities on the site of up to 2.16m/s are predicted by the JFLOW model during the 1 in 100 year event and up to 5.07m/s during the 1 in 1000 year event. As with depth, the highest velocities are in the north eastern corner of the site which is adjacent to Westholme Road.

4.5 Surface Water Drainage and Flood Risk The Site M1 is low lying relative to surrounding topography and the Auction Mart site has previously been flooded with floodwater standing on the site. Floodwater has been deep in parts of the site. NYCC has one record in the vicinity on Westholme Road noted as Swinney Beck overflow causing the flooding. However, surface water runoff is also likely to contribute to the flooding. There are no other DG5 or fire and rescue service records. The surface water flood map indicates that there may be problem areas (caused by ponding in low areas) within Site M1. It is likely that some storage of floodwater is currently taking place on the Auction Mart site for more extreme flood events. The Environment Agency may view this as floodplain. Site M3002 has flat topography. Lower spots on the site close to Swinney Beck may be prone to ponding according to the surface water flood map.

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The Flood Map for Surface Water (FMfSW) shows that surface water flooding to both sites is minimal as shown in Figure 4-7. There is no deep (>0.3m) surface water flooding predicted on either site.

Figure 4-7: Surface Water Flood Map

4.6 Summary

4.6.1 Auction Mart (M1) The Auction Mart, in Masham (site M1), has a history of flooding. The site has been observed to be on the flow path between Swinney Beck and the River Ure during flood events in 1976 and 2000 flood water flowed down Fearby Road onto the site. The Environment Agency Flood Zones (November 2011) include most of the site in Flood Zone 3 (92%) and all of the site in Flood Zone 2. These outlines were developed using a combined approach of JFLOW and HECRAS extended sections. The JFLOW model output underpinning the Flood Zones includes depth and velocity. This indicates that the maximum depth and velocity on the site are high for both a 1% and 0.1% AEP flood event. The average values in the flooded area are lower but in combination the average Hazard category for the flooded part of the site is 'Danger to Most' for a 1% AEP event and 'Danger to All' for a 0.1% AEP event. Surface water flooding has been identified as a risk on a small part of the site, this suggests that infiltration rates may be slow and the site may not be suitable for SUDs. Fearby Road and the A6108 are flooded in places in a 1% event. The Flood Zones are less extensive to the south of the site and access routes in this direction would be lower risk.

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Key Issues • Flood zones are extensive developed by combining a JFLOW 2D model and a HECRAS model to capture the extent of historic flooding on the site. • Site has been observed to be on the flow path of flood events in 1976 and 2000. Modelled flood depth and velocities are high and the average Hazard has been categorised as 'Danger to Most' in the 1% AEP event (Flood Zone 3) and 'Danger to All' in the 0.1% AEP event (Flood Zone 2). This indicated that evacuation of the site and/or emergency services access during a flood event may not be possible. • Blockage of the Swinney Beck channel and Swinney Beck High Bridge has been identified as contributing to the historic flooding in Masham, including the Auction Mart. These are not included in the Flood Zones and under these scenarios the flood risk at the site could increase.

4.6.2 Site M3002 Site M3002 is adjacent to Westholme Road and The Oaks. Part of the site is included in the Environment Agency Flood Zones (Flood Zones 2 and 3) flooding from Swinney Beck. Flooding has not been specifically reported on the site however it is currently undeveloped. Masham has a history of flooding from Swinney Beck. The maximum depth and velocity (from the JFLOW modelling underpinning the Flood Zones) is high, however the average Hazard category is 'Very Low Hazard' for the 1% AEP event (Flood Zone 3) due to low average depths of 0.2m. In the 0.1% AEP event the increased depth and velocity mean that the Hazard category is 'Danger for Most'. There may be some ponding of surface water on the site and the proximity of Swinney Beck suggest that SUDs may not be a suitable way of managing surface water risk. The existing access routes to the site (particularly Westholme Road) are part of the flood flow paths through Masham and access to the site is likely to be restricted during flood events. Key Issues • Part of the site is at risk of flooding in a 1% AEP event at 0.1% AEP event. In a 1% AEP event the depth is relatively low (average depth 0.2m) and the overall Hazard is 'Very Low'. In a 0.1%AEP event the Hazard is identified as 'Danger to Most' suggesting emergency services access may be possible. • Access to the site during a flood event is likely to be restricted. Swinney Beck runs between the site and Westholme Road and access to the site from this direction would be over Swinney Beck Bridge and Foxholme Lane. This area has been modelled as deep floodwater in both a 1% and 0.1% AEP event. The bridge adjacent to the site is shown in Figure 2-4 and has a low arch over Swinney Beck.

4.7 Exception Test Summary The Exception Test must be applied if the sequential testing process cannot identify enough sites where flood risk is low. Harrogate Borough Council have produced the Harrogate District Site and Policies DPD Flood Risk Sequential Test summarising their Sequential Testing process. This has identified some sites where the Exception Test will be required and several others where, although the Exception Test may not be required there is uncertainty about whether development can be made safe. The Exception Test has three requirements: Part A - It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared. If the Local Plan has reached the ‘submission’ stage (see Figure 4.1 of PPS12: Local Development Frameworks and NPPF) the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal (SA); Part B - The development must be on developable previously-developed land or, if it is not on previously-developed land, that there are no reasonable alternative sites on developable previously-developed land; and

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Part C - A site-specific Flood Risk Assessment must demonstrate that the development will be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. Part A will be demonstrated by Harrogate BC based on their development needs identified in their Core Strategy16. Site M1 has been used as an Auction Mart and is therefore 'previously developed' land and will pass Part B of the Exception Test. Site M3002 is currently empty, the history of any development on this site is not known and Harrogate BC must determine whether it is classed as greenfield, in which case it will not pass part B of the Exception Test. A full Flood Risk Assessment for a specific development proposal is required to pass Part C of the Exception Test and the information in this Level 2 SFRA can only be used to indicate whether it is likely that the site will pass. Key issues at each site have been summarised in section 4.6.

4.7.1 Auction Mart (M1) The Auction Mart site (M1) has a history of flooding, lying on a flow path from Swinney Beck to the River Ure. Most of the site is in Flood Zone 3, flood depths are typically between 0.5 and 1m in a 1% event and in combination with the water flow velocity flood hazard at the site is assessed as Danger to Most/ Danger to All. In a 0.1% event the flood hazard has been assessed as Danger to All. Flooding at the site is influenced by blockage of Swinney Beck and if this occurs risk would increase further. Development on the site would also require compensatory storage and could potentially displace additional floodwater into the surrounding residential areas. The cost of mitigation measures is likely to be very high. This Level 2 SFRA indicates that it is not possible to demonstrate that Site M1 would pass Part C of the Exception Test based on current information. Particular issues are: • Site classed as Danger to Most/ Danger to All due to depth and velocity of floodwater in a 1% event. This would make emergency evacuation/ access for emergency services very difficult. • Flooding on roads around the site would also limit access during a flood event. • Development of site is likely to displace floodwater into adjacent areas and could block flood flow routes through the area, increasing existing risk.

4.7.2 Site M3002 18% of site M3002 is in Flood Zone 3a with a further 44% in Flood Zone 2. Figure 4-4 and Figure 4-5 show that the flood risk is concentrated on the north and west sides of the site. In a 1% event the overall Hazard has been identified as low. In a 0.1% event this increases to Danger for Most due to the increase in depth and velocity of floodwater in some parts of the site. The current access to the site (over Swinney Beck) is in the area of highest flood risk. It is likely that a carefully planned development, avoiding higher risk areas and including safe access routes could pass Part C of the Exception Test and be made safe. Harrogate Borough Council must consider whether the safer parts of the site are adequate for the number of new homes required in Masham (see section 1.3.2). The developer must consider the likely cost of mitigation measures which could be high, including the need for off site compensatory storage if there is development in higher risk parts of the site. The developer must now demonstrate that their site specific development proposals avoid the areas of highest risk and address the main concerns in order for their plans to pass Part C of the Exception Test. Key issues are: • Deep, fast flowing water on the north and western edges of the site particularly in the 0.1% event could restrict access during a flood event. Nearby roads are also flooded and this could make site evacuation difficult during a flood event. • Swinney Beck also floods downstream of the site and displaced flood water must not increase this risk.

16 Harrogate Borough Council, Core Strategy, Adopted February 2009. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 40

4.8 Flood Risk Assessment Recommendations Development sites in Masham are likely to be classified as either greenfield or brownfield sites. For example, Site M3002 is likely to be greenfield. The Site M1 at or close to the auction mart is likely to be a greenfield or brownfield development depending on the final location chosen.

4.8.1 Surface water pathways and flooding Historic flooding has been caused by overland flood pathways originating from Swinney Beck and the FRA should therefore investigate overland flood pathways from Swinney Beck. Two locations may be particularly susceptible which are Swinney Beck Bridge and Swinney Beck High Bridge. Blockage of either of these bridges could potentially cause flooding at Site M3002 or Site M1. Detailed modelling based on survey of the topography and preferential flood flow routing is likely to be required for this study. The model should link the river channel (1D) to the floodplain (2D) to represent all the spills from the channel. The model should also be based on detailed up to date survey of the Swinney Beck channel including structures, topographic survey of the main flow routes should also be carried out to confirm that the LIDAR is accurate and identify features that may be influencing the flow pathways (e.g. kerbs and walls). It may also be possible to obtain local anecdotal evidence. The Flood Risk assessment should investigate scenarios including blockage of Swinney Beck High Bridge, Swinney Beck Bridge and the culvert downstream of site M3002. The FRA should also consider whether flood risk is sensitive to channel maintenance, it was found to be overgrown in places on the site visit and it is not known whether siltation is significantly affecting the channel over time. There should also be detailed consideration of the proposed site levels in relation to the simulated and/or observed overland flow paths. Depending on levels floodwater may tend to either pond on the proposed site in a managed way and/or bypass the site.

4.8.2 Surface water runoff An investigation of sewer capacity is advised which should include discussions with Yorkshire Water about the proposed discharge. The existing system may be susceptible to surcharge under storm events. The new development must consider the impact of development on the existing infrastructure and development. The Environment Agency has recommendations for reducing the impacts of surface water runoff and discharge from new development. SUDs The Environment Agency is keen to promote the use of Sustainable Urban Drainage systems (SUDs) and draws attention to the National Planning Policy Framework and associated Technical Guidance. SUDs tackle surface water run-off problems at source using features such as soakaways, permeable pavements, grassed swales, infiltration trenches, ponds and wetlands, and, green roofs to attenuate flood peak flows, produce water quality improvements and environmental enhancements. The Environment Agency seeks to promote the use of SUDs techniques to this site and expect the developer of the site to submit detailed investigations such that the use of SUDs has been fully explored. The suitability of SUDs should be questioned for Site M1 since this area has been prone to historic standing water. Infiltration rates may be low and this would need to be verified by on- site testing. Owing to the flat topography and proximity to Swinney Beck the suitability of SUDs should also be carefully considered for Site M3002. Brownfield sites There must be no increase in surface water runoff from the site. As a consequence of climate change and recommendations in the Pitt Review the Environment Agency would want to see as a minimum a 30% reduction in surface water discharge from the site, for any new development. Further consideration should be given to further regulating the discharge to the greenfield run-off from a 1 in 1 year storm (1.4 l/s/ha) and sufficient storage at least to accommodate a 1 in 30 year storm. The design should also ensure that storm water resulting from a 1 in 100 year event, plus 30% to account for climate change, and surcharging the 2011s5357 HBC Level 2 SFRA FINAL_August 2013 41

drainage system can be stored on the site without risk to people or property and without overflowing into the watercourse or the surrounding area of Masham. Greenfield sites There must be no increase in surface water runoff from the site. As a minimum the Environment Agency would want to see any surface water discharge restricted to the existing greenfield runoff rate. The greenfield runoff rate should preferably be calculated but in cases where this is more difficult to estimate, then the greenfield run-off from a 1 in 1 year storm (1.4 l/s/ha) should be used. The applicant must also provide sufficient attenuation and long term storage at least to accommodate a 1 in 30 year storm. The design should also ensure that storm water resulting from a 1 in 100 year event, plus 30% to account for climate change, and surcharging the drainage system can be stored on the site without risk to people or property. On site long term storage Long term storage is required to mitigate the effects of additional volume of surface water runoff that a developed site will generate. The need for it is most easily identified by calculating the difference between the runoff volumes for the greenfield versus developed site in a 6 hour, 100 year event (as per Interim Code of practice for SUDs) Ideally, comparisons will be carried out over a time series of events. The magnitude of this volume will be influenced by the site soil type, in itself the parameter which determines greenfield runoff volume. The idea is that this additional volume spills from the attenuation storage to an area which drains very slowly – i.e. the long-term storage. To achieve the necessary slow drain down, infiltration is needed. If this cannot be achieved with the use of SUDs systems, then a maximum discharge of 2 litres/sec/ha will be allowed into the drainage system. However, this figure will need to be agreed with Yorkshire Water plc. In the case of an extreme event causing surcharge of the long term storage the overland flow paths of surface water should be considered so as not to cause flooding problems elsewhere. It may be necessary to store this excess water on the site.

4.9 Development Recommendations

4.9.1 Site Layout Auction Mart (Site M1) Most of this site is in Flood Zone 3. Deep flooding is modelled at the northern edge of the site and this should be avoided. Other flood routes from Fearby Road onto and across the site identified in a FRA should also be avoided. Westholme Road (Site M3002) Development should be focussed on the parts of the site in Flood Zone 1. Access routes which are safe during a flood event should be built into the development.

4.9.2 Emergency Planning Auction Mart (Site M1) Access routes to this site are also in the Flood Zones. Evacuation routes and access for emergency services should be planned for the development. Westholme Road (Site M3002) Access to the site from Foxholme Lane and Westholme Road are modelled as flooding from Swinney Beck. This could restrict access to the site during a flood event. Safe evacuation routes and emergency service access should be developed. Part of the site is in a flood warning area and this could be extended to enable evacuation of the site in the early stages of a flood event.

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4.9.3 Floodplain compensatory storage The development of sites M3002 and M1 and the consequent remodelling (e.g. raising) of ground levels may result in the loss of floodplain storage. Requirements for alternative flood storage volumes will need to be discussed and agreed with the Environment Agency.

4.9.4 Channel Maintenance Swinney Beck channel is small and was overgrown in places on the site visit in October 2011 (see Figure 2-4). Maintenance of the channel was identified as an issue in the Section 105 survey (see Table 4-1) and blockage of Swinney Beck High Bridge was identified as a factor in the flooding in 2000 and 2002. This indicates that the condition of Swinney Beck channel has an influence on flood risk in Masham and that FRA scenarios should include blockage and reduced management in Swinney Beck.

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5 Ripon – Auction Mart Site (R10) River Ure and River Skell

5.1 Introduction Site R10 (Auction Mart) is in north east Ripon near to North Bridge on the right bank of the River Ure. The site is bordered by North Road to the north, Princess Road to the south west and Magdalen’s Road to the south east. The site location is shown in Figure 5-1. The southern part of the site is Greenfield and the northern part is Brownfield (this part of the site was used as an auction mart previously). The site covers an area of 2.64Ha. The Level 1 SFRA recommended avoiding development on the site as the entire site was in Flood Zone 2, the predicted flood depths were greater than 1m in some parts of the site (for the 1 in 1000 year event) and flooding of nearby roads would make access very difficult in a flood event. Surface water flood maps indicate that in addition to the risk of flooding from the river there is also a risk of surface water flooding. Since the Level 1 SFRA was completed the EA have updated their flood model for Ripon, this includes the recently completed defences and has more detailed (2D) modelling of water flow across the floodplain. This has been used to investigate flood risk to the site in more detail The site has been identified as a draft allocation in the sites and policies DPD. The exception test is not required for housing development in Flood Zone 2.

© 2013 Nokia © 2013 Microsoft Corporation

Figure 5-1 Site R10 Location

The site slopes from east to west with the lowest areas in the south western part. In addition there is a channel running from north to south across the site. This was identified as a potential flood flow path in the level 1 SFRA.

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© Crown Copyright. All rights reserved. Environment Agency, 100024198 2013.

Figure 5-2 Site R10 topography

Historic flood outlines were supplied by the Environment Agency for the Level 2 SFRA. The outlines show only a small proportion of the site flooding in the south west corner (<1% of the total site area). This flooding may be surface water related as it affects an isolated area away from the River Ure and the River Skell. There is no other flood history information for the site

Figure 5-3 Observed Flood Outline

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5.2 Flood Risk from Rivers Flood risk at site R10 was investigated using updated flood outlines provided by the Environment Agency from their Ripon model. This provides an updated and improved assessment of flood risk at the site including the defences and the flow across the flood plain. This will be used to guide future planning decisions and recommendations at the site. The key assumptions are: • The latest EA ISIS-TUFLOW model results are robust and accurate • The existing hydrology and channel geometry within the ISIS model are appropriate

Given the size of the river systems within the model (River Ure and Skell/Laver), it has not be assumed that both systems will experience the same size flood event at the same time. For the design runs, the 1 in 5 year return period has been simulated on the Skell/Laver system while the full range of return periods investigated (1 in 5 to 1 in 1000 year) were simulated on the River Ure and vice versa. Two versions of the model were configured; defended (including the new flood defence scheme at North Bridge) and undefended. The R10 site is not predicted to flood for the undefended scenario with a 1 in 100 year return period simulated on either river system. In fact the site is not predicted to flood for the defended or undefended scenario up to and including the 1 in 200 year return period at all. For events up to and including the 1 in 200 year return period, flooding does occur from the River Ure to the north west of the site but due to local topography flood water does not extend further than River View Road/Magdalen’s Road. In the event of flooding near to the site, egress routes from the site are clear and the site could be evacuated safely if necessary via North Road. Understanding the role of flood defences in reducing risk at the site is important. Defences can be breached or overtopped and their effectiveness relies on continued maintenance and management. Defences on the rivers close to site R10 are shown in Figure 5-4. The flood risk at site R10 has been assessed with and without these defences (sections 5.3 and 5.4).

Figure 5-4 Defences on the River Ure and Skell close to site R10

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5.3 Flood Risk from the River Ure In a 0.1% AEP event, an event that has a 1 in 1000 probability of occurring in any year, site R10 floods from the River Ure. The river overtops its right bank upstream of North Bridge. Water flows in a south easterly direction alongside the river until it reaches North Road. At North Road some of the flow enters the north east corner of the site and flows across the site in a south westerly direction.

5.3.1 Current Flood Risk – with Defences The flow route across the site is via depression running across the site and the water is deep in some places; the maximum depth near the existing building on the site is around 1m and water ponds at the western edge of the site where flood depths are predicted to reach 1.3m. Figure 5-5 shows the predicted depth of flooding from the River Ure and the velocity of floodwater during the 0.1% AEP event (with defences in place). This is the existing risk at the site. These figures show: • Flood depth up to 1.59m • High velocity of flood water

a. Predicted depth of flooding at R10 site during River Ure 0.1% AEP defended event

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b. Predicted peak velocities at R10 site during River Ure 0.1% AEP defended event

Figure 5-5 Current Flood Risk at Site R10 - Depth and Velocity

5.3.2 Role of Defences Understanding the role of flood defences in reducing risk at the site is important. Defences can be breached or overtopped and their effectiveness relies on continued maintenance and management. The Ripon flood model was used with no flood defences in place to assess the risk to site R10 from the River Ure. This found that the mechanism and route of flooding was the same as the defended (current) scenario but that the flood extent, depth and velocities were greater. This demonstrates that the defences reduce risk at the site.

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Figure 5-6 Depth and Velocity of Flooding at site R10 for an undefended 0.1% AEP flood event

Table 5-1 compares the defended and undefended scenarios. This shows that the defences: • reduce maximum flood depth by 0.76m • reduce mean depth by 0.47m • reduce the percentage of the site flooded by 14% • reduce the maximum velocity

5.3.3 Flood Hazard The predicted depths and velocities for site R10 for flooding from the River Ure are shown in the table below. Table 5-1 Predicted flood depths on site R10 for 1 in 1000 year event on the River Ure Scenario Maximum Mean depth Maximum % of site depth of of flooding velocity on flooded flooding to on site (m) site (m/s) site (m) Defended 1.59 0.52 2.14 56 Undefended 2.35 0.99 2.19 70

The flood Hazard Matrix (shown section 4.2.4.) uses the depth and velocity of flood water to assess the flood hazard. For flooding from the River Ure the maximum flood hazard on site R10 is ‘Danger for All’.

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5.4 Flooding from the River Skell In a 0.1% AEP flood event (an event which has a 1 in 1000 chance of happening in any year) site R10 is also at risk of flooding form the River Skell. During a flood event water from the River Skell flows into the site from the south and ponds at the western edge.

5.4.1 Existing Flood Risk – With Defences Figure 5-7 shows the flood depths and velocities for site R10 during a modelled flood event with a 1 in 1000 chance of occurring in any year. This shows the deeper and faster flowing water on the western side of the site.

a. Predicted depth of flooding at R10 site during River Skell 1 in 0.1% AEP defended event

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b. Predicted peak velocities at R10 site during River Skell 0.1% AEP defended event

Figure 5-7 Flood depth and velocities from the River Skell in a 0.1% AEP defended flood event

For the defended scenario (i.e. existing risk) the flood model shows: • Flood depths of up to 1.9m on the western side of the site and greater than 1m near to the existing building on the site • Peak flood velocities are high, greater than 0.5 m/s on the western side of the site

The combination of deep water flowing with high velocities means that the flood hazard is high, particularly on the west of the site.

5.4.2 Role of Defences The Ripon flood model was used without defences to assess the flood risk to the site from the River Skell in the absence of defences. This shows: • The extent of flooding without defences is not significantly greater than the flood extent for the defended scenario (Figure 5-8) • The depth of flooding on the site is deeper and velocities are greater, these are shown in Table 5-2

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Figure 5-8 Predicted depth of flooding at R10 site during River Skell 0.1% AEP undefended event

5.4.3 Flood Hazard The predicted depth and velocity of flood water at site R10 from the River Skell are shown in the table below. A flood depth of 1.25 – 2.5m is considered as significant i.e. dangerous for most people. Table 5-2 Predicted flood depths on site R10 for 0.1%AEP event on the River Skell Scenario Maximum Mean depth Maximum % of site depth of of flooding velocity on flooded flooding to on site (m) site (m/s) site (m) Defended 1.93 0.75 1.88 57 Undefended 2.15 0.90 2.71 62

The flood Hazard Matrix (shown section 4.2.4.) uses the depth and velocity of flood water to assess the flood hazard. For flooding from the River Ure the maximum flood hazard on site R10 is ‘Danger for All’.

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5.5 Summary of fluvial flood risk to the site Although the site is not predicted to be at risk during the 1 in 100 year event for either the defended or undefended scenario, there is significant flood risk across the site during the 1 in 1000 year event whether defended or undefended. The 1 in 1000 year event outline for the site produced by the latest modelling study is smaller than the existing Flood Zone 2 as shown in Error! Reference source not found.. However, over 50% of the site is predicted to flood during all the 1 in 1000 year scenarios leaving limited area available for development away from the areas at risk of flooding. Flood depths and flow velocities are high leading to a flood hazard of ‘Danger to All’ on some parts of the site. The defences reduce the flood depth and velocity, but maximum flood hazard is still ‘Danger to all’. The defences slightly reduce the flood extent.

Figure 5-9 Comparison of latest 1 in 1000 year food outline with existing Flood Zone 2

Flood risk from the River Ure and River Skell has been assessed separately for this investigation to better understand the flow paths. Flooding from both rivers affects the western side of the site and flow across the middle of the site. Water from the River Ure flows in from the north and water from the River Skell flows in from the south, in an actual flood event the balance of these flow directions will depend on the exact timing of flood peaks and combined flood events on the site would need to be investigated in detail in a site FRA. The extent of flooding is similar in a River Ure and River Skell flood event (56% and 57%), peak velocities are higher for River Ure flooding but water is deeper from the River Skell. There is flooding to surrounding roads during these events this could make access difficult with the south-eastern end of the site (that is not predicted to flood) being cut off during a flood event. Access and egress to and from the site is available via North Road but there is no clear route to Magdalen’s Road on the south eastern side of the site. The high flood depths

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and velocities predicted on the site for the 1 in 1000 year event mean that passing across the site towards North Road from the south eastern side of the site would be hazardous. Key Issues: • Deep flooding on the western side of the site and in a channel running approximately north south across the site. Hazard category ‘Danger to All’. • Risk of flooding from both the River Ure and River Skell • Risk of deep flooding isolating parts of the site 5.6 Surface Water Flood Risk Site R10 is susceptible to surface water flooding. The Level 1 SFRA provided an estimate that 10-50% of the site is susceptible to surface water flooding17; this figure was based on the Areas Susceptible to Surface Water Flooding (ASTSWF) maps which have since been superseded by the Flood Map for Surface Water (FMfSW). The current risk of surface water flooding is shown in Figure 5-10 which shows the 200 year and 30 year Flood Map for Surface Water (FMfSW) respectively. These show: • Approximately 3.5% of the site at risk of surface water flooding in the 30 year shallow flooding scenario (Depth <0.3m, >0.1m). • The shallow 200 year surface water flood extent is larger with 18% of the site affected.

Most surface water flood risk is on the western part of the site with a significant area in the central part of the site also shown to be at risk.

17 Table 7.2, North West Yorkshire Level 1 SFRA Volume II: Technical Report, JBA, 2010. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 54

a. 200 Year Flood Map for Surface Water Flooding

b. 30 Year Flood Map for Surface Water Flooding

Figure 5-10 Surface Water Flood Risk at site R10

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5.7 Climate Change The Environment Agency have provided flood outlines for climate change scenarios, these allow a 20% increase in flow to account for change in future peak flows. The 1% AEP event (an event which has a chance of 1 in 100 of occurring in any year) plus climate change does not lead to flooding on the site. The contribution of climate change to a 0.1% AEP event (chance of 1 in 1000 of occurring in any year) is very uncertain but likely to increase the extent of flooding and/ or the depth of floodwater.

5.8 Impact of Development on Flood Risk Elsewhere Site R10 (Auction Mart) does not flood from either the River Skell or the River Ure for fluvial flood events up to and event with a 1 in 200 chance of happening in any year and, development on the site would not impact on flood risk elsewhere in Ripon. It is only for the fluvial 1 in 1000 year event that flooding is predicted to the site. During this event the predicted depth of flood water on the site is high and should development take place on the parts of the site at risk of flooding there would be a large volume of water displaced. This would increase the flood risk in the surrounding areas. However if development on the site is directed away from the areas at risk of flooding then this is unlikely to increase risk elsewhere. Given the proportion of the site affected by flooding in the 1 in 1000 year event, it is likely that at least part of the development would be planned within the flood outline in which case the displacement of water would need to be mitigated on site to prevent worsening flood risk elsewhere. The impact of development on flood risk elsewhere would depend on the detailed location and design of the development and would need to be considered in detail at in the FRA for the development. There is a greater chance of flooding from surface water but the extent and depths are fairly small, and it is likely that if development were to occur on the site, the surface water could be managed using Sustainable Urban Drainage Systems (SUDS) to mitigate the impact of the development on flood risk elsewhere.

5.9 Exception Test Summary The Exception Test must be applied if the sequential testing process cannot identify enough sites where flood risk is low. Harrogate Borough Council has produced the Harrogate District Site and Policies DPD Flood Risk Sequential Test summarising their Sequential Testing process. This has identified some sites where the Exception Test will be required and several others where, although the Exception Test may not be required there is uncertainty about whether development can be made safe. The Exception Test has three requirements: Part A - It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared. If the LDD has reached the ‘submission’ stage (see Figure 4.1 of PPS12: Local Development Frameworks) the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal (SA); Part B - The development must be on developable previously-developed land or, if it is not on previously-developed land, that there are no reasonable alternative sites on developable previously-developed land; and Part C - A site-specific Flood Risk Assessment must demonstrate that the development will be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. Part A will be demonstrated by Harrogate BC based on their development needs identified in their Core Strategy18. Site R10 is currently empty, part of the site has previously been used as an auction mart and Harrogate BC must determine whether the remainder is classed as greenfield, in which case it will not pass part B of the Exception Test.

18 Harrogate Borough Council, Core Strategy, Adopted February 2009. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 56

A full Flood Risk Assessment for a specific development proposal is required to pass Part C of the Exception Test and the information in this Level 2 SFRA can only be used to indicate whether it is likely that the site will pass.

5.10 Flood Risk Assessment Recommendations Site R10, Auction Mart, is close to the River Ure. The historic flood outline shows flooding on the southern part of the site in an event in 1947. The cause of this is not known, flood water from both the River Ure and River Skell can reach this part of the site. It is also susceptible to surface water flooding and may have been caused by a combination of high river levels and a surcharged surface water drainage system. The nearest flooding record is to the east side of Magdalene's Road in the River Ure floodplain. There are no DG5 flooding records in the vicinity. The site benefits from flood defences, these are shown in Figure 5-4. The River Ure defences have recently been completed and are currently in good condition. Defences on the River Skell include a small flood basin upstream on the River Laver. The effectiveness of the defences depends on their condition and operation, maintenance of defences in the long term is important for managing flood risk at this site. The site is brownfield development.

5.10.1 Flood Risk from Rivers The flood risk to the site has been assessed for the SFRA using flood outlines provided by the EA from their Ripon model. This was designed to provide an overview of flood risk across Ripon and is adequate for the SFRA. The model includes a 2D representation of flow across the flood plain and has identified the main flood routes and flow directions. For a site specific FRA it is recommended that a more detailed model is used, in particular the cell size used in the ISIS-TUFLOW model is 8m. This is a relatively large cell size. A detailed modelling study would be required for any FRA undertaken for the site using a smaller cell size (2 or 4m). The detailed model should be used to investigate: • The flood risk at the site from a joint River Ure, River Skell flood event. In particular the balance between the flow directions across the site. The Environment Agency should be consulted about the choice of River Ure and River Skell flood events to be jointly assessed. • The impact of the specific development on flood risk elsewhere

5.10.2 Surface water runoff An investigation of sewer capacity is advised, this should include discussions with Yorkshire Water about the proposed discharge. The site is located close to the river and the system may be prone to surcharge under storm events. The new development must consider the impact of development on the existing infrastructure and development. The Environment Agency has recommendations for reducing the impacts of surface water runoff and discharge from new development. SUDs The Environment Agency is keen to promote the use of Sustainable Urban Drainage systems (SUDs) and draws attention to the National Planning Policy Framework and associated Technical Guidance. SUDs tackle surface water run-off problems at source using features such as soakaways, permeable pavements, grassed swales, infiltration trenches, ponds and wetlands, and, green roofs to attenuate flood peak flows, produce water quality improvements and environmental enhancements. The Environment Agency seeks to promote the use of SUDs techniques to this site and expect the developer of the site to submit detailed investigations such that the use of SUDs has been fully explored. The suitability of SUDs will need to be assessed for Site R10. In particular the soil conditions and groundwater levels for the lowest parts of the site are important factors. Groundwater levels may be high during flood conditions. Further information about SUDs and Drainage is provided in Appendix A. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 57

Brownfield sites Development must not increase the surface water runoff from the site. As a consequence of climate change and recommendations in the Pitt Review the Environment Agency would want to see, as a minimum, a 30% reduction in surface water discharge, for any new development, on the site. Further consideration should be given to further regulating the discharge to the greenfield run-off from a 1 in 1 year storm (1.4 l/s/ha) and sufficient storage at least to accommodate a 1 in 30 year storm. The design should also ensure that storm water resulting from a 1 in 100 year event, plus 30% to account for climate change, and surcharging the drainage system can be stored on the site without risk to people or property and without overflowing into the watercourse. On site long term storage Long term storage is required to mitigate the effects of additional volume of surface water runoff that a developed site will generate. The need for it is most easily identified by calculating the difference between the runoff volumes for the greenfield versus developed site in a 6 hour, 100 year event (as per Interim Code of practice for SUDs) ideally comparisons will be carried out over a time series of events. The magnitude of this volume will be influenced by the site soil type, in itself the parameter which determines greenfield runoff volume. The idea is that this additional volume spills from the attenuation storage to an area which drains very slowly – i.e. the long-term storage. To achieve the necessary slow drain down, infiltration is needed. If this cannot be achieved with the use of SUDs systems, then a maximum discharge of 2 litres/sec/ha will be allowed into the drainage system. However, this figure will need to be agreed with Yorkshire Water plc.

5.11 Development Recommendations

5.11.1 Site Layout An exception test is not required to build housing within the area of the site covered by flood zone 2. If the site is developed, building should be focused on the areas outside the 1 in 1000 year flood extent, these are the north west and south east sides of the site. Defra have produced a document titled ‘Flood Risks to People – Phase 2 (FD2321/TR2). This uses the concepts of flood hazard in combination with area vulnerability and people vulnerability. It is recommended that this is investigate in some detail across the site and used to inform the layout and design of any development.

5.11.2 Emergency Planning There is some flooding on access routes to the site. Access and egress to and from the site is available via North Road but there is no clear route to Magdalen’s Road on the south eastern side of the site. The high flood depths and velocities predicted on the site for the 1 in 1000 year event mean that passing across the site towards North Road from the south eastern side of the site would be dangerous and development on this part of the site could be cut off. The site is within an existing flood warning area and any new development should use this service to enable timely evacuation of the site in a flood event.

5.11.3 Channel and Defence Maintenance The site benefits from EA defences, which reduce the depth and velocity of flooding. Maintenance of these defences is part of the management of flood risk at the site.

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6 Ripon - River Laver at Bishopton

6.1 Introduction Site R32 is in Bishopton to the west of Ripon. The information available for the Level 1 SFRA indicated that 60% of the site was in Flood Zone 2 and at risk of flooding from surface water. During the Level 1 SFRA study the EA revised the flood zones and reduced the extent of Flood Zone 3 in this area leaving less than 1% of the site at risk of flooding. The site slopes down from the north towards the river, the location and topography are shown in the figure below.

Figure 6-1 - Site R32 Location and Topography

Historic flood outlines were supplied by the Environment Agency for the Level 2 SFRA. The outlines show that site R32 flooded during an event in January 1995 when the River Laver overtopped its banks. During this event a small area at the south western edge of the site was flooded (1.33%), the 1995 flood outline is shown in Figure 2-1. There are no other floods shown to affect the site in the historic flood outlines.

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Figure 6-2 1995 Observed Flood Outline

6.2 Existing Flood Risk

6.2.1 Extent of Flooding Flood risk at site R32 was investigated using the existing EA Ripon ISIS model. This models the site as a reservoir with four spills from the river into the area. Key assumptions are: • The existing hydrology and channel geometry within the ISIS model are still appropriate • The representation of the floodplain in the 1D model (through the use of reservoir units in ISIS) is accurate It should be noted that the ISIS model was developed for a study covering the whole of Ripon rather than a detailed local investigation. However there are no defences or structures that influence flood risk at the site, flood risk at the site may be influenced by the heavily wooded areas on the left bank of the River Laver which may slow flood water overtopping in this areas. Flood risk at the site was found to be influenced by flood plain storage on the opposite bank of the River Laver. The floodplain has not been modelled in 2D and detailed flow routes are therefore not identified in the model. This would need further detailed investigation if part of proposals for any development on the parts of the site is in Flood Zones 2/3. Flood outlines for three events (1%, 1% plus Climate Change and 0.1% AEP) were derived by projecting the peak water levels across the site, using updated LIDAR data to represent the topography. These outlines assume that the peak water level is maintained across the site and therefore provide a conservative estimate of the flood extent. Linked 1D- 2D modelling with more detailed representation of the river banks and floodplain would provide a more accurate indication of locations where flood water over tops the banks and how it flows across the flood plain. These outlines show: • The 1% flood outline is very similar to Flood Zone 3

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• The 0.1% flood outline is smaller than Flood Zone 2, showing water entering the site at the west and ponding in a low lying area. The total area flooded is 0.45 Ha (compared to 5.1 Ha in Flood Zone 2) These outlines are shown in the figures below. Climate change is also shown and this is discussed in section 6.3.

Figure 6-3 Comparison of 1% flood event and 1% plus climate change event with Flood Zone 3

Figure 6-4 Comparison of Modelled 0.1% event with Flood Zone 2

6.2.2 Depth of Flooding The risk associated with flooding depends on the depth of the floodwater. The projected outlines were used to assess flood depth for the 1%, 1% plus climate change and 0.1% scenarios. The maximum and mean depth are summarised in the table below. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 61

Table 6-1 Summary of Flood Depths (site R32) Return Period Maximum depth on Mean depth of % of site flooded flooding to site (m) flooding on site (m) 1% AEP 0.17 0.08 <1 1% + CC AEP 0.29 0.12 <1 0.1% AEP 0.66 0.17 6

This shows that the flood depths are significant but only a small proportion of the site is flooded. The following figures show flood depths across the site.

Predicted flooding on site

R32 Site Predicted Peak Flood Depths (m) 0 - 0.2m 0.2 - 0.4m

0.4 - 0.6m 0.6 - 0.8m 0.8 - 1m

Above 1m

Figure 6-5 Flood Depths in a Modelled 1% Flood Event

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Predicted flooding on site

R32 Site Predicted Peak Flood Depths (m) 0 - 0.2m 0.2 - 0.4m 0.4 - 0.6m 0.6 - 0.8m 0.8 - 1m Above 1m

Figure 6-6 Flood Depths in a Modelled 1% plus Climate Change Event

Figure 6-7 Flood Depths in a Modelled 0.1% Flood Event

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For each of the events in Table 6-1, the deepest predicted flooding is in the south-west corner of the site where the River Laver is closest to the site boundary. The projected 0.1% AEP outline includes a flow route across the site from the western edge and water entering the site here flows until it ponds in a low level area on the site.

6.3 Climate Change The projected 1%+CC AEP event outline is slightly bigger than the projected 1% AEP outline, both outlines are shown in Figure 6-3 along with the current Flood Zone 3. This suggests in the future a 1% flood event is unlikely to cover a significantly larger proportion of the site.

6.4 Impact of Development on Downstream Flood Risk Development in an area at risk of flooding can displace flood water and increase flood risk elsewhere. This was modelled as a simple scenario where no flooding was allowed onto site R32. The results from this scenario showed that there was no increase in water levels in the channel adjacent to or downstream of site R32. There was an increase in flooding over the right bank of the channel and onto the floodplain on the opposite side of the river from the site. This indicates that if the site were to be developed, the increase in water to the floodplain on the opposite bank of the River Laver would need to be considered. Flood storage on the right bank floodplain is shown by the model to be much greater than the flood storage on the left bank floodplain (the R32 site) for the current situation. However, if the right bank floodplain were developed as well as the left bank floodplain (R32 site) this would increase water levels in the channel and is likely to increase flood risk to areas downstream. If the R32 site is developed, the potential for compensatory storage on the right bank floodplain would need to be investigated further.

6.5 Surface Water Drainage and Flood Risk This is a greenfield site. The current use of the site is for agriculture. Since the site is not currently developed it is unlikely that there are DG5 or fire and service records. There has been residential development to the north of the site in Bishopton. Off Ash Bank Road the NYCC data shows that the capacity of the drainage system was exceeded in a storm event. The northern part of the site has a plateau with a flatter slope generally at approximately 1 in 125. The southern part of the site has a steeper fall towards the river. Any flooding problems that may occur to the north of the site within the housing estate may have an impact on the site. Surface water runoff is generally towards the River Laver on the southern boundary of the site. Modelling of surface water runoff indicates that there may be problem areas within Site R32. These are localised and caused by low depressions within the site, overall the site slope towards the river and runoff should be managed via careful landscaping. Figures 3-3 and 3-4 show the 200 year and 30 year storm event Flood Map for Surface Water (FMfSW) respectively. The 200 year shallow (<0.3m, <0.1m depth) surface water flooding covers the greatest extent on the site and shows approximately 10% of the site flooded. The Level 1 SFRA states that >50% of the site is susceptible to surface water flooding19. This figure was based upon the Areas Susceptible to Surface Water Flooding (ASTSWF) maps which has since been superseded by the Flood Map for Surface Water Flooding (FMfSW) as presented here.

19 Table 7.2, North West Yorkshire Level 1 SFRA Volume II: Technical Report, JBA, 2010. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 64

R32 Site River Laver 200 year deep surface water flooding (FMfSW) Depth > 0.3m 200 year surface water flooding (FMfSW) 0.3m > Depth > 0.1m

Figure 6-8 200 Year Flood Map for Surface Water Flooding

R32 Site River Laver 30 year deep surface water flooding (FMfSW) Depth > 0.3m 30 year surface water flooding (FMfSW) 0.3m > Depth > 0.1m

Figure 6-9 30 Year Flood Map for Surface Water Flooding

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6.6 Exception Test Summary The Exception Test must be applied if the sequential testing process cannot identify enough sites where flood risk is low. Harrogate Borough Council has produced the Harrogate District Site and Policies DPD Flood Risk Sequential Test summarising their Sequential Testing process. This has identified some sites where the Exception Test will be required and several others where, although the Exception Test may not be required there is uncertainty about whether development can be made safe. The Exception Test has three requirements: Part A - It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared. If the LDD has reached the ‘submission’ stage (see National Planning Policy Framework and associated Technical Guidance) the benefits of the development should contribute to the Core Strategy’s Sustainability Appraisal (SA); Part B - The development must be on developable previously-developed land or, if it is not on previously-developed land, that there are no reasonable alternative sites on developable previously-developed land; and Part C - A site-specific Flood Risk Assessment must demonstrate that the development will be safe, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. Part A will be demonstrated by Harrogate BC based on their development needs identified in their Core Strategy20 . Site R32 is currently empty, the history of any development on this site is not known and Harrogate BC must determine whether it is classed as greenfield, in which case it will not pass part B of the Exception Test. A full Flood Risk Assessment for a specific development proposal is required to pass Part C of the Exception Test and the information in this Level 2 SFRA can only be used to indicate whether it is likely that the site will pass. Flood risk on most of site R32 is low. Development of the site appears to increase the flood risk on the opposite bank of the river (which is not developed) and does not increase downstream flood risk. The climate change assessment indicates that the extent of a 1% event is unlikely to increase significantly in the future. The modelling found that flood risk on the site is sensitive to assumptions about flood plain storage on the opposite bank on the river and this should be considered carefully at the site design stage. Modelled flood depths are typically less than 0.5m on the site. The evidence collected for this Level 2 SFRA suggests that development on site R32 could be made safe by avoiding areas of higher flood risk. Some earth moving as part of the development may help in this respect. Alternatively, it is possible to carry out some earthmoving to fill in the low depressions to minimise the risk of surface water ponding on the site. Development on this site does not increase flood risk elsewhere as the existing flood plain storage on the south western bank of the river is able to accommodate some additional water. This indicates that a carefully planned development on this site could pass Part C of the Exception Test.

6.7 Recommendations for the Preparation of Flood Risk Assessments This section presents recommendations for site specific flood risk assessments. The LPA and Environment Agency should be consulted in order to scope the content and level of the FRA. The SFRA has assessed flood risk at a strategic level, which can be used to provide baseline evidence for a FRA. However, where a more detailed FRA is required the developer should undertake a detailed assessment of the flood risk to the site, using the SFRA to scope out flood risk issues, the NPPF and its associated Technical Guidance and CIRIA Report Development and Flood Risk. Developers should satisfy themselves that the data provided in the SFRA is up-to-date and accurate for their development.

20 Harrogate Borough Council, Core Strategy, Adopted February 2009. 2011s5357 HBC Level 2 SFRA FINAL_August 2013 66

The modelling work carried out for this study supports the updated extent of Flood Zone 3 produced by the EA during the Level 1 SFRA. Additional work suggests that the extent of the flood outline to include climate change is slightly larger than Flood Zone 3 but still smaller than Flood Zone 2. This study also suggests that the area at risk of flooding in a future 1% event is smaller than Flood Zone 2. It should be noted that all of these outlines are sensitive to the floodplain storage available on the opposite (right) bank of the River Laver. Updated site specific modelling is recommended for the FRA. This will take the proposed housing layout and proposed topography into consideration. It should also include details of the floodplain on the right bank of the river. Therefore, a linked 1D-2D model with more detailed representation of flood plain flow and storage is recommended for a site specific FRA.

6.7.1 Surface water flooding Overland surface water flow paths will need to be considered in the development of the housing layout. This will need to include the surface water flow paths arising from and flowing within the new development. It will also need to consider surface water runoff from the existing residential area to the north of any proposed development. It was noted in Section 6.5 that surcharge of the drainage systems has occurred on Ash Bank Road and this is the type of problem that will need to be considered.

6.7.2 Site drainage It is likely that surface water from the new development will be routed directly into the River Laver. The new development must consider the impact of surface water discharge on existing infrastructure and development. The Environment Agency has recommendations for reducing the impacts of surface water runoff and discharge from new development. Development Site R32 is likely to be treated as a greenfield site for the design criteria of the surface water drainage. SUDs The Environment Agency is keen to promote the use of Sustainable Urban Drainage systems (SUDs) and draws attention to the NPPF and its associated Technical Guidance. SUDs tackle surface water run-off problems at source using features such as soakaways, permeable pavements, grassed swales, infiltration trenches, ponds and wetlands, and, green roofs to attenuate flood peak flows, produce water quality improvements and environmental enhancements. The Environment Agency seeks to promote the use of SUDs techniques to this site and expect the developer of the site to submit detailed investigations such that the use of SUDs has been fully explored. The suitability of SUDs will need to be assessed for Site R32. In particular the soil conditions and groundwater levels for the lowest parts of the site are important factors. Groundwater levels may be high during flood conditions. Further information about SUDs and Drainage is provided in Appendix A. Greenfield sites There must be no increase in surface water runoff from the site. As a minimum the Environment Agency would want to see any surface water discharge restricted to the existing greenfield runoff rate. The greenfield runoff rate should preferably be calculated but in cases where this is more difficult to estimate, then the greenfield run-off from a 1 in 1 year storm (1.4 l/s/ha) should be used. The applicant must also provide sufficient attenuation and long term storage to accommodate a 1 in 30 year storm as a minimum within the drainage system. The design should also ensure that storm water resulting from a 1 in 100 year event, plus 30% typically to account for climate change, and surcharging the drainage system can be stored on the site without risk to people or property and without overflowing into the watercourse. On site long term stormwater storage Long term storage is required to mitigate the effects of additional volume of surface water runoff that a developed site will generate. The need for it is most easily identified by calculating the difference between the runoff volumes for the greenfield versus developed site

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in a 6 hour, 100 year event (as per Interim Code of practice for SUDs). However, comparisons should be carried out over a time series of storm events to determine the critical volume required. The magnitude of this volume will be influenced by the site soil type, in itself a parameter which determines greenfield runoff volume. It is intended that additional volume that spills from the attenuation storage is held in an area which drains very slowly – i.e. the long-term storage. To achieve the necessary slow drain down, infiltration is needed. If this cannot be achieved with the use of SUDs systems, then a maximum discharge of 2 litres/sec/ha will be allowed into the drainage system. However, this figure will need to be agreed with Yorkshire Water plc.

6.7.3 Role of floodplains The flood risk at site R32 is influenced by the floodplain extent on the opposite bank of the River Laver. Developers should consider this in more detail using a linked 1D-2D model to understand in detail the role that these areas play in reducing flood risk on the site and, once the site has been developed, mitigating any impacts further downstream.

6.8 Development Recommendations

6.8.1 Site Layout An exception test is not required to build housing within the area of the site covered by Flood Zone 2. If the site is developed, building should be focussed on the north and east parts of the site in Flood Zone 1.

6.8.2 Emergency Planning Flood Zones 2 and 3 show flood risk on the southern edge of the site only (see Figure 3-2) and access to the site would still be possible from the north and east. If the site is to be developed, any emergency egress routes should focus upon people leaving the site via the higher ground to the north and east of the site.

6.8.3 Channel maintenance The River Laver has poor channel capacity below the site. The risk to the new development in the southern part of the site must be considered alongside measures to open up the channel and increase conveyance.

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Appendices A Appendix - Sustainable Drainage Systems

A.1 Assessment of the Application of SUDS Sustainable Drainage Systems (SUDS) are management practices which enable surface water to be drained in a more sustainable manner. For Greenfield developments, the aim is to not increase runoff from the undeveloped situation; for Brownfield re-developments, the aim is to reduce existing runoff rates. Wherever possible, this should be achieved through the implementation of a sustainable drainage or flow retention systems, constructed within the boundaries of the development site. There are many different SUDS techniques. As a result, there is no one correct drainage solution for a site. In most cases, a combination of techniques, using the Management Train principle, will be required. Figure A1 shows the SUDS Management Train principle where source control is the primary aim. Just as in a natural catchment, drainage techniques can be used in series to change the flow and quality characteristics of the runoff in stages. The management train starts with prevention, for individual premises, and progresses through local source controls to larger downstream site and regional controls. Runoff need not pass through all the stages in the management train. It could flow straight to a site control, but as a general principle it is better to deal with runoff locally, returning the water to the natural drainage system as near to the source as possible. Only if the water cannot be managed on site should it be conveyed elsewhere. This may be due to the water requiring additional treatment before disposal or the quantities of runoff generated being greater than the capacity of the natural drainage system at that point. Excess flows would therefore need to be routed off site. The design of SUDS will require active decisions between different options, often depending on the risks associated with each course of action. The risks of an area flooding have to be balanced with the costs of protecting the area from different levels of floods. The management train concept promotes division of the area to be drained into sub-catchments with different drainage characteristics and land uses, each with its own drainage strategy. Dealing with the water locally not only reduces the quantity that has to be managed at any one point, but also reduces the need for conveying the water off the site.

Figure A1: SUDS Management Train Principle21

21 CIRIA (2008) Sustainable Drainage Systems: promoting good practice – a CIRIA initiative SUDS can reduce the amount and rate of runoff by a combination of: Infiltration, Storage, and Conveyance

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There are a number of SUDS techniques which may be. However their suitability relies on site conditions, such as permeability and ground water levels, as summarised in Table A1.

Table A1: Suitability of SUDS Techniques SUDS Technique Infiltration Storage Conveyance Green Roofs x v v Permeable Paving v x v Rainwater Harvesting x v x Swales v v v Detention Basins v v v Ponds x v v Wetlands x v v

Source: PPS25 Practice Guide now replaced with the NPPF and associated Technical Guidance

NPPF and associated Technical Guidance stresses that Local Planning Authorities (LPAs) should: • Promote the use of SUDS for the management of run-off • Ensure their policies and decisions on applications support and complement the Building Regulations on sustainable rainwater drainage, giving priority to infiltration over first watercourses then sewers • Adopt policies for incorporating SUDS requirements in Local Development Documents • Encourage developers to utilise SUDS wherever practicable, if necessary through the use of appropriate planning conditions • Develop joint strategies with sewerage undertakers and the Environment Agency to further encourage the use of SUDS

A.2 SUDS Guidance For further information on the design of SUDS see CIRIA publications (www.ciria.org): • Interim Code of Practice for SUDS • C521 : SUDS design manual for Scotland and N. Ireland (2000) • C522 : SUDS design manual for England and Wales (2000) • C523 : SUDS - best practice Manual (2001) • C582 : SUDS - Source control using constructed pervious surfaces (2002) • C609 : SUDS - hydraulic, structural and water quality advice (2004) • C625 : Model Agreements for SUDS (2004) • C697 : The SUDS Manual (2007) • C698 : Site Handbook for the Construction of SUDS (2007)

A.3 Drainage for new developments Development has the potential to cause an increase in impermeable area, an associated increase in surface water runoff rates and volumes, and a consequent potential increase in downstream flood risk due to overloading of sewers, watercourses, culverts and other drainage infrastructure. It should be borne in mind that sewer networks may have been designed to drain less development than exists today. Controlling surface water discharges from new development is a crucial consideration if flood risk to new and existing development is to be effectively managed. Planned development can also play a role in reducing the number of properties that are directly at risk from surface water 2011s5357 HBC Level 2 SFRA FINAL_August 2013 II

flooding. The Planning System has a key role to play in settings standards for sustainable drainage from new developments and ensuring that developments are designed to take account of the risk from surface water flooding. Sustainable drainage plays an important part in reducing flows in the sewer network and in meeting environmental targets, alongside investment in maintenance and new capacity by Yorkshire Water, in consultation with key partners, including the Environment Agency. Wherever possible, this should be achieved through the implementation of SUDS. Source control should be considered firstly. There may be opportunities to deliver SUDS though integrated solutions for collections of strategic sites. The future ownership and maintenance of SUDS systems should be discussed at the planning application stage with the relevant sections of the LPA (including Highways and Drainage), Yorkshire Water and the Environment Agency. The developer should liaise closely with the local authority drainage engineer, the Environment Agency and Yorkshire Water to determine appropriate discharge rates. The developer should prove that surface water discharges from the site will not have an adverse impact on flood risk elsewhere, with reference to investment planning by Yorkshire Water that may increase the capacity of the sewer network in the area. All proposals for development must consider how surface water will be effectively controlled, and also propose SUDS techniques to fully attenuate surface water generated on the development site. The aim of this approach is to prevent any increase in surface water discharge to receiving watercourses or drainage infrastructure and prevent any increase in flood risk as a result of development. The planning system has a key role to play in settings standards for SUDS from new developments and ensuring that developments are designed to take account of the risk from surface water flooding. Sustainable drainage and the use of SUDS is supported by the policy direction in Future Water (Defra, 2008), Making Space for Water (Defra, 2008), the Pitt Review and the Flood and Water Management Act (2010) that provides for more sustainable management of the water cycle, working in partnership across different agencies and new responsibilities for local flood risk management. In particular, the Flood and Water Management Act requires developers where practical, to include sustainable drainage in new developments to reduce flood risk and improve water quality. It includes ‘a requirement on developers to demonstrate that they have met national standards for the application of SUDS techniques before they can connect any residual surface water drainage to a public sewer (amending section 106 of the Water Industry Act 1991).’ As part of their new responsibility for local flood risk management, local authorities will be responsible for approving SUDS for new developments and adopting and maintaining them. Recognising the above, drainage from new developments should incorporate storage, with residual discharge of surface water to the following networks in order of preference: 1. Infiltration drainage (e.g. soakaways). 2. Discharge to a watercourse 3. Discharge to a public sewer The choice of system will be determined by local ground conditions (including groundwater levels). Whilst infiltration SUDS may be the most suitable for new development, developers must consider the risk of contamination to underlying aquifers Local flood risk management will be an important responsibility for local authorities in the future, which includes managing the risk of flooding from surface water, groundwater and ordinary watercourses. Many of the localised flooding problems can be related to local watercourses that have been culverted as past development has taken place. The condition and standard of protection of these watercourses are unknown but they can be a significant source of flood risk. Flooding in the urban environment is difficult to separate into distinct sources and in reality surface water flooding will be from a combination of overland flows, sewers and highways gullies backing up and surcharging at manholes, local watercourses overtopping, culverts surcharging and potentially high groundwater levels. This is one reason why it is important for one body (the local authority) to take the lead in local FRM delivery.

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A.4 Suitability of Sites for Infiltration/SUDs The potential suitability of sites identified in this SFRA, in terms of infiltration/SUDS, will need to be assessed. The suitability of ground conditions including, for example, seasonal groundwater levels and soil permeability will need to be determined prior to development. If sites are confirmed to be of low suitability the development will need to include sustainable solutions that do not depend on infiltration. As indicated in Annex F of PPS25 now superseded by the NPPF and associated Technical Guidance, several SUDS storage alternatives may be suitable for sites where permeability is poor, and infiltration is not deemed appropriate. There include: • Source control measures including rainwater recycling and drainage • Filter strips and swales, which are vegetated features that hold and drain water downhill mimicking natural drainage patterns • Basins and ponds to hold excess water after rain and allow controlled discharge that avoids flooding.

A.5 Critical Drainage Areas Certain locations are particularly sensitive to an increase in the rate and volume of surface water runoff from new development. There are generally known local flooding problems associated with these areas. North Yorkshire County Council (NYCC) are the Lead Local Flood Authority (LLFA) and are currently investigating and prioritising areas of surface water flood risk. This may lead to development of Critical Drainage Areas (CDAs) in collaboration with the Environment Agency and Yorkshire Water. There are currently no CDAs in the SFRA study areas.

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References

Flood Risk Assessment DCLG (2012) National Planning Policy Framework (Crown copyright) (available from www.gov.uk) DCLG (2012) technical Guidance to the National Planning Policy Framework (Crown copyright) (available from www.gov.co.uk) Defra, Department for Transport, HM Treasury and Office of the Deputy Prime Minister (2005) Making Space for water: Taking forward a new Government strategy for flood and coastal erosion risk management in England; First Government response to the autumn 2004 Making space for water consultation exercise Defra (2008) Future Water Defra (2009) Surface Water Management Plan Guidance version 0.1 Defra (2010) Flood and Water Management Act © Crown Copyright Defra (2006) Flood Risks to People. EA/Defra R&D document FD2321 Defra (2005) Flood Risk Assessment Guidance for New Development. EA/Defra R&D document FD2320 Supplementary Note on Flood Hazard Ratings and Thresholds for Development Planning and Control Purpose – Clarification of the Table 13.1 of FD2320/TR2 and Figure 3.2 of FD2321/TR1. (http://randd.defra.gov.uk/Document.aspx?Document=FD2321_7400_PR.pdf) www.environment-agency.gov.uk www.gov.uk www.defra.gov.uk www.communities.gov.uk www.statistics.gov.uk www.ukcip.org.uk The Pitt Review (2008) Learning lessons from the 2007 floods

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