LAND TO THE SOUTH OF BRAMSHALL ROAD … Application...Weetwood 41 St Pauls Street Leeds LS1 2JG t:...

Weetwood

41 St Pauls Street

Leeds

LS1 2JG

t: 0113 244 1377

e: [email protected]

w: www.weetwood.net

LAND TO THE SOUTH OF BRAMSHALL ROAD

UTTOXETER

FLOOD RISK ASSESSMENT Final Report v1.0

October 2013

lisa.roberts

Text Box

P/2013/01287 Received 12/11/13

Land to the south of Bramshall Road, Uttoxeter Flood Risk Assessment report

©Weetwood

www.weetwood.net

i 2353/FRA Final v1.0

29 October 2013

Report Title: Land to the South of Bramshall Road, Uttoxeter

Flood Risk Assessment Final Report v1.0

Client: Gleeson Strategic Land

Date of Issue: 29 October 2013

Yeshentha Naidoo BEng MSc Prepared by:

Senior Technical Engineer

Jenny Cavill BSc Checked by:

Associate Director

Kevin Tilford BSc MSc PhD MBA C.WEM MCIWEM CEnv Approved by: Director

This document has been prepared solely as a Flood Risk Assessment for Gleeson Strategic

Land. Weetwood Services Ltd accepts no responsibility or liability for any use that is made of

this document other than by Gleeson Strategic Land for the purposes for which it was originally

commissioned and prepared.


©Weetwood

www.weetwood.net

ii 2353/FRA Final v1.0

29 October 2013

CONTENTS

Page Signature Sheet

Contents List of Tables, Figures & Appendices

i

ii iv-vi

1 INTRODUCTION............................................................... 1

1.1 Site Location .............................................................................................1 1.2 Existing and Proposed Development .............................................................1 1.3 Site Levels ................................................................................................2 1.4 Access and Egress......................................................................................2

2 NATIONAL PLANNING POLICY FRAMEWORK ......................... 3

2.1 Flood Zone Designation ..............................................................................3 2.2 Flood Risk Sequential Test...........................................................................3 2.3 Development and Flood Risk........................................................................4

3 FLOOD RISK ................................................................... 5

3.1 Historical Records of Flooding ......................................................................5 3.2 Fluvial Flood Risk .......................................................................................5 3.3 Flood Risk from Reservoirs and Canals..........................................................7 3.4 Groundwater Flooding ................................................................................8 3.5 Surface Water Flooding...............................................................................9

4 MITIGATION MEASURES ................................................. 12

4.1 Flood Mitigation .......................................................................................12 4.2 Access and Egress....................................................................................12 4.3 Flood Warning .........................................................................................12 4.4 Main River...............................................................................................12

5 SURFACE WATER MANAGEMENT ...................................... 14

5.1 Requirements for Surface Water Drainage...................................................14 5.2 Site Areas ...............................................................................................14 5.3 Surface Water Runoff from the Existing Site ................................................15 5.4 Surface Water Runoff from the Developed Site ............................................15


©Weetwood

www.weetwood.net

iii 2353/FRA Final v1.0

29 October 2013

6 SUMMARY..................................................................... 19

7 RECOMMENDATIONS...................................................... 20


©Weetwood

www.weetwood.net

iv 2353/FRA Final v1.0

29 October 2013

LIST OF TABLES

Table 1: Picknall Brook Modelled Flood Levels.......................................................6 Table 2: Site Areas .........................................................................................15 Table 3: Total Peak Runoff Rate – Existing Site...................................................15 Table 4: Total Peak Runoff Rate – Developed Site ...............................................16


©Weetwood

www.weetwood.net

v 2353/FRA Final v1.0

29 October 2013

LIST OF FIGURES

Figure 1: Site Location.......................................................................................1 Figure 2: Digital Elevation Model.........................................................................2 Figure 3: Environment Agency Flood Map.............................................................4 Figure 4: Historic Flood Maps .............................................................................5 Figure 5: Picknall Brook Modelled Node Locations .................................................6 Figure 6: Projected Peak Flood Levels..................................................................7 Figure 7: Environment Agency Risk of Flooding from Reservoirs Map.......................8 Figure 8: BGS Groundwater Flooding Hazard Map .................................................9 Figure 9: Environment Agency Surface Water Flood Maps ....................................10 Figure 10: Environment Agency Flood Warning Flood Alert Map .............................13


©Weetwood

www.weetwood.net

vi 2353/FRA Final v1.0

29 October 2013

LIST OF APPENDICES

Appendix A: Development Proposals Appendix B: Topographic Survey

Appendix C: Greenfield Runoff Rate Calculations Appendix D: Storage Volume Calculations


©Weetwood

www.weetwood.net

1 2353/FRA Final v1.0

29 October 2013

1 INTRODUCTION

Weetwood has been instructed by Gleeson Strategic Land to undertake a Flood Risk Assessment (FRA) for the proposed development of land to the south of Bramshall Road, Uttoxeter. The assessment has been undertaken in

accordance with the requirements of the National Planning Policy Framework (NPPF).

1.1 SITE LOCATION

The site is located off Bramshall Road at Ordnance Survey National Grid Reference SK 078 335, as shown in Figure 1. The site is split into two parcels

- parcel A is approximately 2.50 hectares (ha) and parcel B is approximately 5.54 ha in area.

Parcel A

© Crown Copyright 2013. All rights reserve d.

Image reproduced with permission of Ordn ance Survey and Ordnance Survey of Northern Ireland

Bramshall Road

Picknall Brook

Parcel B

Figure 1: Site Location

1.2 EXISTING AND PROPOSED DEVELOPMENT

The majority of the site comprises of undeveloped agricultural land. A small

area of Parcel B is occupied by farm buildings (Roycroft Farm).


©Weetwood

www.weetwood.net


29 October 2013

The proposals are for the refurbishment of the existing farm buildings and for a residential development of up to 140 houses (see illustrative masterplan in Appendix A). The NPPF classifies residential development as ‘more

vulnerable’ land use1.

1.3 SITE LEVELS

A topographic survey of the site has been undertaken by BluePlan and is provided in Appendix B. The site slopes from north to south from 108.6 m AOD in the north to 85.6 m AOD in the south, as shown in Figure 2.

Parcel A

Parcel B

Figure 2: Digital Elevation Model

1.4 ACCESS AND EGRESS

The site is accessed via Bramshall Road. Bramshall Road slopes downwards from west to east, with levels between 108.5 m AOD in the west and 103.5 m

AOD in the east.

1 NPPF, Technical Guidance, Table 2


©Weetwood

www.weetwood.net


29 October 2013

2 NATIONAL PLANNING POLICY FRAMEWORK

The aim of the NPPF is to ensure that flood risk is taken into account at all stages in the planning process and is appropriately addressed.

2.1 FLOOD ZONE DESIGNATION

The NPPF2 defines flood zones as follows:

• Flood Zone 1: Low Probability. Land assessed as having a less than 1

in 1000 annual probability of river or sea flooding in any year.

• Flood Zone 2: Medium Probability. Land assessed as having between a 1 in 100 and 1 in 1000 annual probability of river flooding or between a

1 in 200 and 1 in 1000 annual probability of flooding from the sea in any year.

• Flood Zone 3a: High Probability. Land assessed as having a 1 in 100 or greater annual probability of river flooding (>1%) or a 1 in 200 or greater annual probability of flooding from the sea (>0.5%) in any year.

• Flood Zone 3b: The Functional Floodplain. Land where water has to flow or be stored in times of flood. The identification of the functional

floodplain should take account of local circumstance and not be defined solely on rigid probability parameters. However, land which would flood with an annual probability of 1 in 20 or greater in any year should

provide a starting point for consideration and discussion.

According to the Environment Agency (EA) Flood Map (Figure 3) most of the site is located in Flood Zone 1 with a small area to the south located in Flood Zone 2 and Flood Zone 3.

East Staffordshire Borough Council published a Level 1 SFRA in February 2008

and a Level 2 SFRA in August 2008. Figure 3 of the Level 2 SRFA confirms the EA flood mapping for the site.

2.2 FLOOD RISK SEQUENTIAL TEST

The aim of the Sequential Test3 is to encourage development to be located in areas at the lowest probability of flooding. A sequential approach has been

applied to site masterplanning, and all built development will be located in Flood Zone 1. As such the Sequential Test has been addressed.

2 Technical Guidance, Table 1 3 NPPF Chapter 10 and NPPF Technical Guidance, paragraphs 3-5


©Weetwood

www.weetwood.net


29 October 2013

© Envir onment Agency copyright and database rights 2013© Ordnance Survey Cr own copyright. A ll rights r eservedEnvi ronment Agency, 100026380 , 2013

FZ3 (1 in 100 year)

FZ2 (1 in 1,000 year)

FZ1 (>1 in 1,000 year)

Legend

Figure 3: Environment Agency Flood Map

2.3 DEVELOPMENT AND FLOOD RISK

The NPPF4 states that for development proposals on sites in Flood Zone 1

comprising 1 hectare or above, the vulnerability to flooding from other sources and the effect of the new development on surface water runoff should be

incorporated in an FRA. Other potential sources of flooding are discussed in Section 3 of this report.

The effect of the new development on surface water run-off is addressed in Section 5.

4 Technical Guidance, Table 1


©Weetwood

www.weetwood.net


29 October 2013

3 FLOOD RISK

3.1 HISTORICAL RECORDS OF FLOODING

According to the EA historic flooding map, a small proportion of the site along the southern boundary flooded in 1977 although Figure 4 of the Level 1 SFRA5 does not confirm this historic flooding (Figure 4).

The British Hydrological Society (BHS) Chronology6 has one record7 of historic

flooding in October 1875 in Uttoxeter. However, the record does not make mention of a specific location where the flooding occurred, so it is unclear whether or not the proposed site was affected.

More recently, there are reports of flooding in Uttoxeter in July 2012. The

flooding was described in one report as “the worst flooding in decades”8. However, according to press reports, the flooding was limited to areas downstream of Hockley Road, including the retail park at Dovefields and

Uttoxeter Racecourse.

EA Historic Flood Map Level 1 SFRA Historic Flood Map – Figure 4

Figure 4: Historic Flood Maps

3.2 FLUVIAL FLOOD RISK

Picknall Brook flows from west to east along the southern edge of the site. Modelled flood levels for Picknall Brook have been obtained from the EA for the 1 in 100 year, 1 in 100 year plus climate change and 1 in 1000 year events.

5 East Staffordshire Borough Council, Level 1 SFRA, February 2008 6 British Hydrological Society Chronology www.dundee.ac.uk/geography/cbhe/ 7 Based on the following keyword searches: Uttoxeter 8 www.uttoxeter-news.co.uk/News/Town-recovers-from-the-torrential-rain-and-floods-10072012.htm


©Weetwood

www.weetwood.net


29 October 2013

Modelled peak flood levels for the modelled nodes illustrated on Figure 5 are provided in Table 1 (the highlighted cells indicate model nodes situated within the site boundary).

Modelled Levels Node Points. Centred on Roycroft Farm, Uttoxeter, Created April 2013.

Ref: C-4870

Modelled Levels Node Points. Centred on Roycroft Farm, Uttoxeter, Created April 2013.

Ref: C-4870

Figure 5: Picknall Brook Modelled Node Locations

Table 1: Picknall Brook Modelled Flood Levels

Peak Water Level (m AOD)

Node 1 in 20 year 1 in 100 year

1 in 100yr plus

cc 1 in 1000yr

2560 84.55 84.73 84.84 85.10

2561 84.73 84.99 85.13 85.34

2562 84.88 85.12 85.23 85.44

2564 85.03 85.28 85.40 85.59

2565 85.20 85.41 85.46 85.62

2566 85.38 85.58 85.67 85.78

2568 85.63 85.86 85.95 86.10

2569 85.95 86.41 86.74 87.63


©Weetwood

www.weetwood.net


29 October 2013

The modelled peak flood levels for the 1 in 100 year and 1 in 1000 year events have been projected on a ground terrain map of the site derived from the site

topographic survey. The derived flood outlines presented on the illustrative masterplan in Figure 6. This demonstrates that all development will be within

Flood Zone 1.

FZ3 (1 in 100 year)

FZ2 (1 in 1,000 year)

FZ1 (>1 in 1,000 year)

Site Boundary

Legend

Figure 6: Projected Peak Flood Levels

3.3 FLOOD RISK FROM RESERVOIRS AND CANALS

Reservoir or canal flooding may occur as a result of the facility being overwhelmed and/or as a result of dam or bank failure.

The EA Risk of Flooding from Reservoirs Map (Figure 7) shows that the site is not in an area considered to be at risk of reservoir flooding.

As such, the site is considered to be at low risk of flooding from these sources.


©Weetwood

www.weetwood.net


29 October 2013

© Environment Agency copyright and database rights 2013© Ordnance Survey Crown copyright. All rights reservedEnvironment Agency, 100026380, 2013

Flooding from reservoirs

Legend

Flooding from reservoirs

Legend

Figure 7: Environment Agency Risk of Flooding from Reservoirs Map

3.4 GROUNDWATER FLOODING

Groundwater flooding generally occurs during intense, long-duration rainfall

events, when infiltration of rainwater into the ground raises the level of the water table until it exceeds ground levels. It is most common in low-lying

areas overlain by permeable soils and permeable geology, or in areas with a naturally high water table.

According to British Geological Survey (BGS) mapping, the northern part of the site is underlain by glaciofluvial sand and gravel and the southern part of

the site underlain by Alluvium (clay, silt, sand and gravel). The bedrock is mudstone (Mercia Mudstone Group).

According to the Soilscapes maps produced by the National Soils Research Institute9 soil conditions at the site and within the surrounding area are

described as “…loamy and clayey soils, with impeded drainage”.

The EA website indicates that there is no superficial aquifer underlying the site but that the site to be underlain by a Secondary B bedrock aquifer. Secondary B aquifers have predominantly lower permeability layers, which may store and

yield limited amounts of groundwater through fissures, thin permeable horizons and weathering.

9 Soilscapes www.landis.org.uk/soilscapes/


©Weetwood

www.weetwood.net


29 October 2013

According to the British Geological Survey (BGS) Groundwater Flooding Hazard map (Figure 8) the northern and southern edges of the site may be

susceptible to groundwater flooding.

The Level 1 SFRA also states ‘there have been very few recorded incidences of groundwater flooding within East Staffordshire’. The SFRA does not list any incidents occurring at the site.

Based upon the above, the overall risk of groundwater flooding is assessed to

be low and will be mitigated through the implementation of the measures proposed in Section 4 of this report.

© Crown Copyright 2013. All rights reserved. Licence number 100047514Derived from 1:50 000 scale BGS Digital Data, British Geological Survey - NERC

Legend

Susceptibility to flooding

from groundwater

Significant

Moderate

Low

Legend

Susceptibility to flooding

from groundwater

Significant

Moderate

Low

Figure 8: BGS Groundwater Flooding Hazard Map

3.5 SURFACE WATER FLOODING

Surface water flooding comprises pluvial, sewer and highway drains and

gullies.


©Weetwood

www.weetwood.net


29 October 2013

3.5.1 Pluvial Flooding

Pluvial flooding results from rainfall-generated overland flow, before the runoff enters any watercourse or sewer, or where the sewerage/drainage systems

and watercourses are overwhelmed and therefore unable to accept surface water. Pluvial flooding is usually associated with high intensity rainfall events

but may also occur with lower intensity rainfall where the ground is saturated, developed or otherwise has low permeability resulting in overland flow and ponding within depressions in the topography.

The EA Areas Susceptible to Surface Water Flooding Map and Flood Map for

Surface Water (Figure 9) indicate that a small proportion of the site near the southern boundary may be susceptible to surface water flooding.

However, although the soil underlying the site may have impeded drainage (refer Section 3.4) the slope of the site would naturally promote surface

runoff and prevent pluvial runoff from occurring to any significant depth. However, no built development is proposed on the susceptible area.

© Environment Agency copyright and database rights 2013© Ordnance Survey Crown copyright. All rights reserved

Environment Agency, 100026380, 2013

Legend

Flood depths from a 1 in

30 year rainfall event

> 0.1m

> 0.3m

Legend



> 0.1m

> 0.3m



Legend



> 0.1m

> 0.3m

Legend



> 0.1m

> 0.3m

1 in 30 Year Flood Map for Surface Water 1 in 200 Year Flood Map for Surface Water

Figure 9: Environment Agency Surface Water Flood Maps

The SFRA does not have a record of surface water flooding occurring at or

within the vicinity of the site. Based on the above, the propensity for pluvial flooding at the site is

considered to be low. However, flood risk from this source will be addressed through the mitigation measures as detailed in Section 4 and the surface

water drainage strategy in Section 5.


©Weetwood

www.weetwood.net


29 October 2013

3.5.2 Sewer Flooding

Sewer flooding can occur when the capacity of the sewer system is overwhelmed by heavy rainfall, becomes blocked or is of inadequate capacity,

resulting in flooding of land and/or property. Normal discharge of sewers and drains through outfalls may be impeded by high water levels in receiving

waters. The SFRA makes no reference of sewer flooding at or within the vicinity of the

site.

3.5.3 Flooding from Highway Drains and Gullies

The SFRA mentions no incidents of highway flooding at or within the vicinity of the site.


©Weetwood

www.weetwood.net


29 October 2013

4 MITIGATION MEASURES

4.1 FLOOD MITIGATION

The flood risk to the site will be mitigated though the implementation of the measures proposed within the following section of this report.

4.1.1 Finished Floor Levels

Finished floor levels should be set at a minimum of 0.15 m above adjacent ground levels following reprofiling of the site.

This will enable any potential surface water to be conveyed safely across the site without affecting property in accordance with the approach promoted

within DEFRA’s Making Space for Water document.

4.2 ACCESS AND EGRESS

Access to the site will be provided via Bramshall Road. This route is shown to be located within Flood Zone 1 and will therefore provide dry access and egress to the site.

4.3 FLOOD WARNING

According to the EA Flood Warning Map (Figure 10), Picknall Brook is in a

Flood Alert Area. Residents of the developed site would therefore be able to access flood

warning information for Picknall Brook from the EA website (www.environment-agency.gov.uk), by calling Floodline on 0845 988 1188 or

via the EA Flood Alert smartphone app. However, the potential extent of flooding from Picknall Brook would not

warrant any conditioning of the planning application with respect to flood warning.

4.4 MAIN RIVER

Picknall Brook is classified as a Main River. The EA has discretionary powers,

within the Water Resources Act 1991, to carry out works to the River for which access must be maintained. The Land Drainage Byelaws require the prior written consent of the EA for ‘Works Affecting Watercourses’ for any proposed

works or structures in, over, under or within a distance of 8 metres from the top of the banks of the River. This shall not be unreasonably withheld.

The layout of the development confirms that there will be a large undeveloped strip of land adjacent to Picknall Brook which will ensure there is more than

adequate access for maintenance purposes.


©Weetwood

www.weetwood.net


29 October 2013



Flood Warning Area

Flood Alert Area

Legend

Flood Warning Area

Flood Alert Area

Legend

Figure 10: Environment Agency Flood Warning Flood Alert Map


©Weetwood

www.weetwood.net


29 October 2013

5 SURFACE WATER MANAGEMENT

5.1 REQUIREMENTS FOR SURFACE WATER DRAINAGE

Surface water arising from a developed site should, as far as is practicable, be managed in a sustainable manner to mimic the surface water flows arising from the site prior to the proposed development.

Development of the site should be such that the peak flow rates of surface

water leaving the developed site are no greater than the rates prior to development. Opportunities to reduce surface water runoff, and the associated flood risk, should also be identified and climate change taken into

consideration.

Recognising the above, and the requirements of the EA10, Building Regulations Approved Document H, the Code for Sustainable Homes Technical Guide (Category 4) and the requirement placed upon local planning authorities within

the NPPF to promote the use of Sustainable Drainage Systems (SuDS), surface water runoff from the proposed site should demonstrate:

• No increase in existing flow rates discharged to watercourse/public sewer

• The use of SuDS as the preferred method of dealing with surface water

• How runoff up to the 1 in 100 year event plus an allowance for climate

change will be dealt with without increasing flood risk elsewhere

SuDS aim to mimic natural drainage and can achieve multiple objectives such as removing pollutants from urban runoff at source, controlling surface water runoff from developments, and ensuring that flood risk is not increased

downstream. Typical SuDS components include surface or subsurface storage with flow limiting devices, roadside swales, detention basins and infiltration

areas or soakaways.

The Level 1 SFRA11 states that, in addition to catering for climate change, a 20% reduction in post development runoff rates is required. It also encourages the use of SuDS for the management of run off. It goes on to

state that successful implementation of SuDS will require the early consideration of a wide range of issues surrounding their management, long

term adoption and maintenance, which should all be considered during the feasibility stage of development.

5.2 SITE AREAS

The existing and proposed impermeable and permeable areas at the site are shown in Table 2. This indicates that the extent of impermeable area at the

site will increase by 2.533 ha following development.

10 Preliminary Rainfall Runoff Management for Developments, R&D Technical Report W5-074/A/TR/1 Revision C, 2005 11 East Staffordshire Borough Council, Level 1 SFRA, February 2008


©Weetwood

www.weetwood.net


29 October 2013

Table 2: Site Areas

Existing Site Developed Site

Impermeable area (ha) 0.098 2.631

Permeable area (ha) 7.942 5.409

TOTAL 8.040 8.040

5.3 SURFACE WATER RUNOFF FROM THE EXISTING SITE

It has been assumed that the undeveloped part of the site currently drains by

gravity towards Picknall Brook by surface runoff and shallow interflow. There are a number of manholes located within the curtilage of the Roycroft

Farm site which suggests that surface runoff from the farm buildings and impermeable areas are positively drained to the 150/225 mm diameter public

surface water sewer along Bramshall Road. However, this has not been confirmed by a drainage survey.

5.3.1 Existing Site Runoff Rate

The peak runoff rates for the existing site are summarised in Table 3. The existing impermeable areas are considered negligible and the site has

been assumed to be entirely greenfield.

Greenfield runoff rates from permeable surfaces have been calculated using the ICP SuDS method within Micro Drainage. Details of the Micro Drainage input parameters and the output results are provided in Appendix C.

Table 3: Total Peak Runoff Rate – Existing Site

Runoff Rate (l/s) Return Period

Impermeable areas Permeable areas Total

1 in 2 year 0.0 41.0 41.0

1 in 30 year 0.0 81.2 81.2

1 in 100 year 0.0 106.1 106.1

5.4 SURFACE WATER RUNOFF FROM THE DEVELOPED SITE

The following sections describe how surface water runoff from the developed site may be managed in accordance with the requirements of the NPPF and

East Staffordshire Borough Council.

5.4.1 Surface Water Discharge Rate

It is proposed to limit runoff rates from the impermeable areas of the developed site to 10.7 l/s (Table 4). This corresponds to a 20% reduction in peak runoff compared to existing rates. Permeable areas will continue to drain

at Greenfield runoff rates.


©Weetwood

www.weetwood.net


29 October 2013

The drainage system for the proposed site will be designed to manage flows in up to the 1 in 100 year event including an allowance for climate change.

Table 4: Total Peak Runoff Rate – Developed Site

Runoff Rate (l/s) Return Period

Impermeable areas Permeable areas Total

1 in 2 year 10.7 27.6 38.3

1 in 30 year 10.7 54.6 65.3

1 in 100 year 10.7 71.4 82.1

Comparison of the total peak runoff rates from the existing site (Table 3) with those from the developed site (Table 4) indicates that development will

provide for significant betterment in terms of reduced surface water flows as encouraged by the NPPF and its supporting Technical Guidance.

5.4.2 Disposal of Surface Water

Building Regulations Approved Document Part H sets out a hierarchy of preferred methods for the disposal of surface water runoff12. These are listed

below in order of preference:

1. Disposal by infiltration: As detailed previously, soils at the site are

characterised as having impeded drainage whilst groundwater levels may be relatively shallow across the site. It is therefore unlikely that infiltration will be a feasible method for disposal of surface water runoff

from the developed site.

2. Disposal to a watercourse: Picknall Brook crosses the southern edge of

the site. The site naturally drains to this watercourse and is the obvious receptor of surface runoff.

3. Disposal to a public sewer: It is not proposed to discharge surface water

runoff from the developed site into the public sewer system.

5.4.3 Surface Water Attenuation

Attenuation storage will be provided to restrict runoff rates from the impermeable areas of the developed site as set out in Section 5.4.1.

The required storage volume has been sized to store the 1 in 100 year storm event including a 30% increase in rainfall intensity in order to allow for climate

change in accordance with the NPPF13.

12 Section 3 page 45 13 NPPF, Technical Guidance – Table 5

Land to the south of Bramshall Road, Uttoxeter

Flood Risk Assessment report

©Weetwood

www.weetwood.net


29 October 2013

The surface water storage facilities described in the following sections have been modelled using the Detailed Design module of Micro Drainage Source Control. The parameters used in the storage calculation along with the Micro

Drainage Source Control output results are provided in Appendix D.

The modelling indicates that a storage volume of 1840 m3 would be required. The storage requirements do not take into account the storage capacity within the on-site surface water pipe system network (which is expected to be

adopted). Consequently, the storage volumes stated below are likely to reduce following detailed design.

Approximately 1,600 m3 of storage could be provided by a detention basin located to the south of the site augmented by a linear swale / detention basin

running north-south to the east of the site, sub-surface cellular storage with permeable paving, under estate roads and parking areas or a combination of

both.

5.4.4 Maintenance of SuDS

In the past local planning authorities and water companies have been

reluctant to adopt SuDS. With no arrangements in place that require local planning authorities or water companies to adopt SuDS their maintenance has

subsequently been the responsibility of the developer. The Flood and Water Management Act (2010) is currently being implemented

through a series of Commencement Orders. Section 32 introduces Schedule 3: Sustainable Drainage. This introduces:

• New standards for the design, construction, operation and maintenance of new rainwater drainage systems

• A new ‘approving body’ (generally a unitary, county or county borough

local authority)

• A requirement for the approving body to approve most types of rainwater

drainage systems before any construction work with drainage implications can start, subject to: (i) the system being constructed in line

with an approved drainage plan to national standards; (ii) the approving body being satisfied the drainage system has been built and functions in accordance with the drainage plan, and (iii) the system being a

sustainable drainage system, as defined by regulations.

However, this provision is awaiting commencement following further work by DEFRA on arrangements for adoption and maintenance of SuDS, including technical guidance. At present it is envisaged that implementation of these

arrangements will be Spring 2014 at the earliest.

In the meantime, other options for maintenance of SuDS include:

• The pipe network, designed to Sewers for Adoption (7th edition) standard, will be adopted by the sewerage undertaker

• Roadside swales will be adopted by the highways authority



©Weetwood

www.weetwood.net


29 October 2013

• SuDS in public open spaces (e.g. dry detention basin) may be adopted by the local authority

• A management company set up by the operators of the site

5.4.5 Summary

The outline surface water drainage scheme presented in this FRA has been

developed to demonstrate that a technically feasible drainage solution exists for the site, given the development proposals and the land available.

The final surface water drainage solution may vary from the illustrative scheme. However, the final scheme should accord with the principles set down

in this FRA, and should be submitted to and approved by the local planning authority prior to the commencement of development.



©Weetwood

www.weetwood.net


29 October 2013

6 SUMMARY

There are proposals for the residential development of land located off Bramshall Road, Uttoxeter.

According to the EA flood map the majority of the site is located within Flood Zone 1, with a small area along the southern edge of the site within Flood

Zones 2 and 3. Picknall Brook flows across the southern edge of the site. Although the brook

would be expected to come out of bank during extreme floods, the extent of any flooding would be limited by the topography of the site.

A sequential approach has been applied to site masterplanning, and all built development would be located in Flood Zone 1. As such the flood risk

Sequential Test has been addressed.

The site may be susceptible to groundwater flooding and flood risk from this source will be managed by the proposed mitigation measures. Flood risk from other sources is not assessed to be significant.

Safe and dry access and egress will be provided via Bramshall Road, which is

located within Flood Zone 1. Following development, impermeable areas at the site will increase. An outline

surface water drainage scheme has been developed which demonstrates that surface water runoff can be sustainably managed on site and that post

development peak runoff rates would be significantly reduced compared to existing (Greenfield) runoff rates.



©Weetwood

www.weetwood.net


29 October 2013

7 RECOMMENDATIONS

This FRA has demonstrated that the proposed development may be completed without conflicting with the requirements of the NPPF and supporting Technical Guidance subject to the following:

• Finished floor levels to be set 0.15 m above adjacent ground levels

• The detailed surface water drainage design, developed in accordance

with the principles set down in this FRA, should be submitted to and

approved by the local planning authority prior to the commencement of development



©Weetwood

www.weetwood.net

2353/FRA Final v1.2

29 October 2013

APPENDIX C:

Micro Drainage Outputs for Greenfield Runoff



©Weetwood

www.weetwood.net

2353/FRA Final v1.2

29 October 2013

APPENDIX D:

Micro Drainage Storage Volume Calculation

Delivering client focussed services

Flood Risk Assessments

Flood Consequences Assessments

Surface Water Drainage

Foul Water Drainage

Environmental Impact Assessments

River Realignment and Restoration

Water Framework Directive Assessments

Flood Defence Consent Applications

Sequential, Justification and Exception Tests

Utility Assessments

Expert Witness and Planning Appeals

www.weetwood.net

LAND TO THE SOUTH OF BRAMSHALL ROAD … Application...Weetwood 41 St Pauls Street Leeds LS1 2JG t:...

Documents

Transcript of LAND TO THE SOUTH OF BRAMSHALL ROAD … Application...Weetwood 41 St Pauls Street Leeds LS1 2JG t:...