Nottinghamshire County Council Environment and Resources Department

Proposed Multi-user Route to Sherwood Pines

Report Reference: P.H.IL.30000.52

Flood Risk Assessment Report

Tim Gregory Corporate Director Environment and Resources Trent Bridge House West Bridgford Nottingham NG2 6BJ

September 2012

CONTENTS

1. INTRODUCTION

1.1 Brief

2. EXISTING SITE

2.1 Location 2.2 Current Land Use 2.3 Flood Risk to the Existing Site

3. PROPOSED DEVELOPMENT

3.1 Development Description 3.2 Development Drainage

4. FLOOD RISK TO THE DEVELOPMENT 4.1 Flood Zone Identification 4.2 Development Vulnerability 4.3 Mitigation 4.4 Flooding Mechanisms 4.5 Climate Change Impact on Sea and Tidal estuary levels

5. CONCLUSIONS

1. INTRODUCTION

1.2 Brief

This Flood Risk Assessment is prepared in accordance with the requirements of the Planning Policy Framework and the Planning Policy Statement (PPS) 25, ‘Development and Flood Risk’ published by the Department of Communities and Local Government. PPS 25 which sets out the framework for planning decisions made by local, regional and national government and the Environment Agency (EA). In order that planning authorities can make informed decisions on the development of sites in areas at risk of flood, PPS 25 requires the developer to carry out an assessment of flood risk.

This report addresses the requirements given in Annex E of PPS 25 and other issues which are deemed relevant to flood risk. These requirements include the following:

• Assess suitability of site and development through the use of the Sequential Test & Exception Test (if required).

• Assessment of the magnitude and severity of flood risk to the site.

• Assess impact of proposed development on flood risk to adjacent developments.

• Determine ability of existing and proposed drainage to accommodate development flows with respect to flooding.

• Demonstrate that appropriate mitigation measures have been taken to prevent flooding.

• Demonstrate that appropriate emergency situations have been considered e.g. overland flow paths, evacuation routes.

2. EXISTING SITE

2.1 Location

The site comprises the disused mineral railway line from Eakring Road in Bilsthorpe (Easting 464812, Northing 361199) to Country Park (Easting 459404, Northing 362598) via Sherwood Pines in Nottinghamshire – shown in red on the plan below.

2.2 Current Land Use

The closest water course to the disused railway line is Water which is located to the west of Bilsthorpe. The railway line traverses Rainworth Water at NGR 464138,361166 in the form of a significant embankment and culvert feature. With the exception of the above small area to the west of Bilsthorpe the remainder of the multi user route way lies exclusively within the Flood Zone 1 area.

2.3 Flood Risk to the Existing Site

2.3.1 Flooding from the Existing Drainage Network

The line of the former mineral track traverses the Rainworth Water floodplain west of Bilsthorpe on one occasion and only for approximately 10m. The Environment Agency (EA) has a requirement that no additional surface water run-off is generated from the proposed development and that the use of SUDS techniques should be considered.

There are currently no known flooding issues related to the existing site drainage although there have been incidents of minor flooding on Eakering Road. Discussions with the Highways Department at Nottinghamshire County Council has indicated that these minor flooding incidents were related to extreme weather events and not related to the normal performance or capacity of the local drainage and public sewer network.

3 PROPOSED DEVELOPMENT

3.1 Development Description

The development proposal is for the construction of a multi user route and associated access to the former mineral railway line.

3.2 Development Drainage

3.2.1 Foul Water Drainage

There is no foul water discharge

3.2.2 Storm Water Drainage

The National Planning Policy Framework which replaced PPS 25 requires that the surface water drainage system for any development is designed such that the peak flow rates of surface water leaving a developed site are no greater that the rates prior to the proposed development. The multi user route will not change the infiltration potential of rainfall as ground cover will not alter to any significant degree, as the former mineral railway track bed will be used in the formation of a multi user route with permeable surface. The materials of construction being rolled ballast and a Red shale top dressing to provide a useable surface.

4.0 FLOOD RISK TO THE DEVELOPMENT

4.1 Flood Zone Identification

The Sequential Test set out on NPPF/PPS 25 requires that different locations are considered for the site in order to best minimise flood risk. The proposed development can be considered as a redevelopment of an existing ‘brownfield’ site. It is therefore considered that this site is appropriate for the proposed development.

PPS 25 also outlines a sequential approach to Flood Risk Assessments for any development, the starting point for which is the identification of the appropriate Flood Zones

Interpretation of the extract from the Environment Agency Flood Mapping, shown below indicates that the proposed development site with the small exception of the embankment crossing Rainworth Water, shown outlined red, lies within Flood Zone 1(little or no risk of flooding), with Flood Zone 2(Medium Probability) and 3 (High probability) only occurring at the crossing of the Rainworth Water. Flood Zone 3 comprises 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 .”

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4.2 Development Vulnerability

NPPF/PPS25 requires the Planning Authority to consider if a development is appropriate on the basis of both the identified Flood Zone, and the level of vulnerability of the proposed development. Table 4.1 below summarises the general approach, and is a reproduction of Table D.3 from PPS 25.

Table 4.1: Flood Risk Vulnerability and Flood Zone Compatibility

Flood Risk Essential Water Highly More Less Vulnerability Infrastructure Compatible Vulnerable Vulnerable Vulnerable Classification Zone 1: Low      Probability Zone 2:   Exception   Medium test required Probability Zone 3a: High Exception test  x Exception  Probability required test required Zone 3b: The Exception test  x x x Functional required Flood Plain (  = permitted, x = not permitted)

The Sequential Test also requires that the suitability of the site for the prescribed use of the proposed development is addressed through the use of Tables D1-D3 in Annex D of PPS 25. The probability of flooding is considered in Table D1 which suggests that the area of the site (in this case the northern access ramp) to be developed lies within Flood Zone 3a.

The proposed development falls into the category of ‘Water-compatible Development’ in Table D2. As Table 4.1 above suggests that this type of development in a Flood Zone 3a is permitted. The requirement for an Exception test is negated

4.3 Mitigation

Issues related to safe access and egress can be addressed through the design of the scheme to ensure that appropriate design measures are incorporated to address issues of flood risk. Indeed the embankment will offer a degree of refuge as the elevation of the embankment which crosses Rainworth Water is at a significantly higher elevation than the surrounding ground.

The site is predominantly located within an area which is not subject to flood risk and as such it is not considered that the development will increase flood risk elsewhere.

4.4 Flooding Mechanisms

From the District Council Strategic Flood Risk assessment report “The flood plain of Rainworth Water is located to the west of the village (Bilsthorpe). The vast majority of the village of Bilsthorpe is situated in Flood Zone 1; the risks posed by fluvial flooding are considered to be minimal”.

4.4.2 Flooding from Land

Flooding from overland flow caused by inadequate drainage in the built-up area is not considered to be a risk in this area. Furthermore the majority of the route is in a rural environment.

4.4.3 Flooding from Groundwater

There is no history of groundwater flooding at this location

4.4.4 Flooding from Sewers

Need to speak with Flood management

4.5 Climate Change Impact

For individual developments, an appropriate allowance should be included over the lifetime of each development in question. Developers are advised to therefore carefully consider, and advise those undertaking flood risk assessments what the design life is; the implications of climate change can then be carefully considered using the precautionary allowances and indicative sensitivity ranges in tables 2.1 and 2.2, of PPS25.

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5. CONCLUSIONS

It is considered that this appraisal represents a comprehensive analysis of the potential flood impact of the development upon other adjacent properties and of existing flood mechanisms on the development itself. It demonstrates that the proposed development is sustainable in terms of flood risk, and can be summarised as follows:

• Interpretation of the Environment Agency Flood Zone Map indicates that with the small exception of the Rainworth Water crossing (Flood Zone 2/3) the alignment of the Multi User Route is wholly within a Flood Zone 1.

• The proposed development is considered as “Water–compatible development” in NPPF/PPS 25 tables D1-2. Furthermore table D3 in PPS 25 suggests that this type of development is appropriate in Flood Zone 3a.

• The primary risk to flooding of the site is from fluvial flooding. There have been no significant incidents of flooding on the site in recent years.

• It is expected that the surface water discharges from the development will not be greater than the existing flows.

• The detailed design of the surface water flow management drainage network will seek to adopt SUDS techniques where appropriate, possible solutions could include filter drains, and permeable pavement in pavement areas.

Based on the findings of this report, it is considered that there are no grounds for objecting to the proposed development in terms of flood risk