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P/2016/01267 Received 12 Sept 2016

St Stephen’s Hill Farm, Flood Risk Assessment 24/03/2016 Version 1.0 RAB: 1291L

Second Floor, Cathedral House, Unit 13, St Stephens Court, Willington, Kingsbrook House, 7 Kingsway, Beacon Street, WS13 7AA Crook, County Durham DL15 0BF Bedford, Bedfordshire MK42 9BA T. 01543 547 303 T. 01388 748 366 T. 01234 363 582

Registered Office: Langard Lifford Hall, Lifford Hall, Lifford Lane, Kings Norton, Birmingham B30 3JN. Registered in England. Company No 5799647. VAT registration No. 884 0481 08

1291L St Stephen’s Hill Farm March 2016 Version 1.0

Revision History

Version Date Amendments Issued to 1.0 24/03/16 M. Pope

Quality Control

Action Signature Date

Prepared P. Batty 07/03/16

Checked G. Wilson 17/03/16

Approved R. Burton 23/03/16

Disclaimer

This document has been prepared solely as a Flood Risk Assessment for Mr P. Brown. RAB Consultants accepts no responsibility or liability for any use that is made of this document other than by the client for the purpose for which it was originally commissioned and prepared. No person other than the client may copy (in whole or in part) use or rely on the contents of this document, without the prior written permission of the Managing Director of RAB Consultants Ltd. Any advice, opinions, or recommendations within this document should be read and relied upon only in the context of the document as a whole.

RAB Office

Lichfield Office Second Floor Cathedral House Beacon Street Lichfield WS13 7AA

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Contents

1.0 INTRODUCTION...... 1 2.0 SITE DETAILS ...... 1 2.1 Site location ...... 1 2.2 Site description ...... 1 2.3 Development proposal ...... 2 3.0 FLOOD RISK ...... 2 3.1 Flooding history ...... 2 3.2 Fluvial (Rivers) ...... 3 3.3 Flood defence breach or overtopping ...... 3 3.3.1. Breach risk...... 3 3.3.2. Overtopping risk...... 3 3.4 Coastal/tidal ...... 3 3.5 Groundwater ...... 3 3.6 Pluvial (Surface water) ...... 5 3.7 Artificial water bodies ...... 6 4.0 MITIGATION MEASURES ...... 6 4.1 Risk to buildings ...... 6 4.1.1. Finished floor levels ...... 6 4.1.2. Flood resistance ...... 6 4.1.3. Flood resilience ...... 7 4.2 Risk to occupiers ...... 7 4.2.1. Safe access/egress ...... 7 4.3 Risk to others...... 7 4.3.1. Floodplain compensation and flood flow routes ...... 7 4.3.2. Surface water run-off ...... 8 5.0 CONCLUSION ...... 9 6.0 RECOMMENDATIONS ...... 9 APPENDIX A – SITE LOCATION & PROPOSED DESIGN ...... 10

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1.0 Introduction

RAB Consultants has prepared this Flood Risk Assessment (FRA) in support of the proposed development at St Stephen’s Hill Farm. The development site is located in Flood Zone 1 in accordance with the Environment Agency’s Flood Map for Planning (Rivers and Sea). The Planning Practice Guidance for the National Planning Policy Framework (NPPF) requires a site specific Flood Risk Assessment to be carried out for developments located in Flood Zones 2 & 3 and for those which are 1 hectare (ha) or greater in size. The site is 1.3ha and therefore a site specific FRA is required to ensure that the development is safe from flooding and will not increase the risk of flooding elsewhere. 2.0 Site details

2.1 Site location

Table 1 – Site location Land at St Stephen’s Hill Farm, Steenwood Lane, Admaston, Site address Rugeley WS15 3NQ Site area 1.3ha Formerly used for growing agricultural crops but is currently Existing land use unused. OS NGR 405609 323055 Local Planning Authority East Borough Council

2.2 Site description

The site in question was formerly used for growing agricultural crops but is currently unused. Access to the site is from a private drive which leads from the B5013 close to the south shore of Blithfield Reservoir.

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Table 2 – Site photographs

1 – VIEW FROM THE SOUTH WEST OF THE SITE LOOKING TOWARDS 2 – VIEW FROM THE NORTH EAST BOUNDARY OF THE SITE LOOKING BLITHFIELD RESERVOIR. SOUTH WEST.

3 – VIEW FROM THE SOUTH WEST OF THE SITE LOOKING TOWARDS BLITHFIELD RESERVOIR. NOTICE THE AREA OF WATERLOGGED 4 – NATURAL DEPRESSION IN THE GROUND TOWARDS THE NORTH GROUND IN THE FOREGROUND OF THE PHOTO, THIS IS DESCRIBED IN EAST OF THE SITE. MORE DETAIL IN SECTION 3.5.

2.3 Development proposal

It is proposed to construct 10 short stay holiday lodges on the site (Appendix A) along with an access track and parking. There will also be some landscaping, planting and the creation of a pond/wetland on site. 3.0 Flood Risk

3.1 Flooding history

The owner has no knowledge of flooding at the site from Blithfield reservoir (knowledge dating back 45 years). The owner believes that the ground level at the site is many metres above the height of the reservoir outfall and consequently flooding at the site is extremely unlikely.

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There is a dry depression in the ground near the southern boundary of the site (Figure 1). The depression filled with water during the rains of summer 2007. It is proposed to landscape the depression to form a pond/wetland and this will be used to provide attenuation to surface water leaving the site. The owner has no other knowledge of significant water collecting on the site over the past 45 years.

FIGURE 1 DRY DEPRESSION IN THE GROUND IN FRONT OF THE TREE

The owner reports that the action of the spring (which enters the site at the southern boundary and is described in section 3.5) has remained constant and does not seem to be subject to seasonal change.

3.2 Fluvial (Rivers)

The River Blithe passes through Blithfield Reservoir which is located 100m north east of the site. The development is within Flood Zone 1 in accordance with the Environment Agency’s flood mapping network. This zone comprises land assessed as having a less than 1 in 1000 annual probability of river or sea flooding in any given year. 3.3 Flood defence breach or overtopping

3.3.1. Breach risk

The site is not protected by flood defences therefore is not at risk from this source. 3.3.2. Overtopping risk

The site is not protected by flood defences therefore is not at risk from this source. 3.4 Coastal/tidal

The site is not located near the coast therefore is not at risk from this source. 3.5 Groundwater

There is a small spring adjacent to the site on the south side which feeds a pond. The flow from the spring/pond enters the site at the southern boundary and quickly infiltrates into the ground forming a damp area of ground (Figure 2).

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FIGURE 2 POINT WHERE THE SPRING ENTERS THE SITE

There is a land drain located close to this water source on the site which assists with conveying this flow (along with any other sub-surface water) to a ditch along the northern boundary of the site (Figure 3).

FIGURE 3 DITCH AT THE NORTHERN SITE BOUNDARY

The flow is then conveyed into the reservoir by a small culvert section and a second ditch (Figure 3 and Figure 4).

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The spring is small and is effectively a groundwater flow through the site. This can be seen by the absence of any channel formed by the flow (Figure 5).

FIGURE 5 GROUNDWATER FLOW PATH THROUGH THE SITE

The site is not expected to be at particular risk from ground water based on the evidence of the site visit, other than wetness in the valley shape along which the spring flow passes. 3.6 Pluvial (Surface water)

According to the Environment Agency’s Surface Water Flooding map the development is at very low risk, less than 1 in 1000 a.p. chance in any given year (Figure 6). The surface water flow passes along the same route as the ground water flow path. The site is not expected to be at particular risk from surface water based on the evidence of the site visit and the absence of any channel formed by the flow.

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FIGURE 6 – SCREENSHOT TAKEN FROM THE ENVIRONMENT AGENCY’S ONLINE SURFACE WATER FLOOD MAP (04/03/16). 3.7 Artificial water bodies

The site is approximately 100m south-west of Blithfield reservoir which is fed by the River Blithe and a number of other small water-courses. The site is several metres above the typical reservoir water level and is within flood zone 1 with a 1 in 1000 or less annual probability of flooding (see Appendix A). The site is not therefore threatened by a breach in the reservoir dam. The reservoir water level is not expected to rise to a level that would flood the site. There are no nearby raised canals therefore the risk is low from this source. 4.0 Mitigation measures

4.1 Risk to buildings

4.1.1. Finished floor levels

The site is several metres above the typical reservoir water level and is within flood zone 1 with a 1 in 1000 or less annual probability of flooding. There are no other significant water-courses that pose a flood risk to the site. For these reasons it is recommended that the buildings are raised at least 300mm above adjacent ground to avoid ingress of any overland water flows. 4.1.2. Flood resistance

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The use of flood resistance measures to protect the ground floor from the risk of flooding is not considered appropriate, given the rarity of flooding and the raised floor level. 4.1.3. Flood resilience

The use of flood resilience measures to protect the ground floor from the risk of flooding in not considered appropriate, given the rarity of flooding and the raised floor level. 4.2 Risk to occupiers

4.2.1. Safe access/egress

Safe and dry access to the site will be maintained in all but the most extreme floods. 4.3 Risk to others

4.3.1. Floodplain compensation and flood flow routes

The site is wholly within Flood Zone 1, therefore the development will have no impact on the floodplain. The surface water flow route through the site should be maintained and construction of holiday lodges within the flow route shown in Figure 7 should be avoided.

FIGURE 7 - SITE LOCATION OVERLAID ON THE ENVIRONMENT AGENCY'S ONLINE SURFACE WATER FLOOD MAP (04.03.16)

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4.3.2. Surface water run-off

The site area is approximately 1.3ha and currently undeveloped. The proposal is to erect 10 holiday lodges which will create a total impermeable area of approximately 200m2. In substantial rainfall events overland flows will follow the gentle natural gradient of the land towards the Blithfield Reservoir. Box 1.2 from the SuDS manual (C753, 2015) discusses the SuDS management train which is intended to mimic the natural catchment process as closely as is possible. Table 6 below gives examples of the hierarchy of techniques that can be used to achieve the management train. Table 6: Hierarchy of SuDS techniques and their descriptions Technique Description Prevention The use of good house design and housekeeping measures to prevent run-off and pollution; rainwater re-use/ harvesting Source control Soakaways, porous and pervious surfaces, water butts, green roofs Site control Routing water to large soakaways, infiltration or detention basins Regional control Balancing pond, wetlands, swales, retention ponds

The feasibility of the above techniques to be incorporated into this development are described in Table 7 below. Table 7: Feasibility of SuDS techniques at the development site Feasibility Technique Issues Y / N / M (Maybe) Prevention Ensuring that drains and guttering are properly Y Good building design and located and laid could enable water to be collected rainwater harvesting for re-use via water butts or water harvesting systems. Source control The use of permeable coverings on walkways and Porous and pervious materials driveways will enable surface water falling onto Y these areas to infiltrate into the ground. Soakaways may provide opportunities for water Soakaways M storage and infiltration within the site. A green roof is beyond the scope of this small Green roof N development. Site/regional control Infiltration/detention basins; It would be feasible to include a strategy of balancing ponds; attenuation on site to restrict runoff rates and treat Y surface water from the site.

In summary, the use of SUDS techniques are recommended for this development. The use of permeable surfaces on developed areas and soakaways would provide an opportunity to deal with surface water close to the development. SUDS conveyance techniques, such as swales, would allow further infiltration and pollution treatment opportunity.

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It is proposed that the access and parking areas will be reinforced grass, therefore surface water will act as existing with no formal surface water drain being required. It is proposed to discharge all runoff from the rooftops into individual traditional soakaways located at the side of each lodge. The system should be designed to cope with 1 in 100 a.p. plus climate change rainfall. The available area appears reasonable for this, however ground testing is recommended to confirm infiltration rates and groundwater levels. It is recommended that the residual risk of the design capacity of the drainage systems being exceeded or of blockage occurring is mitigated by shaping the ground to keep flooding away from lodges and direct surface water towards the wetland area to the north of the site. 5.0 Conclusion

Planning consent is sought for the construction of 10 short stay holiday lodges on land at St. Stephen’s Hill Farm. The development is within flood zone 1 of the Environment Agency flood map and there is no history of flooding at the locations of the lodges. The development will include the provision of a SUDS drainage scheme which will ensure surface water runoff continues to act as if the site was greenfield. It is concluded that the proposed development is appropriate for the flood risk and is not expected to increase the risk of flooding elsewhere. 6.0 Recommendations

 Set floor levels 300mm above the local finished ground level to avoid ingress of any overland water flows.

 Locate holiday lodges outside of the surface water flow route.

 Commission a SUDS drainage scheme in line with the recommendations given in Section 4.3.2.

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Appendix A – Site Location & Proposed Design

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