Tandridge District Council Level 2 Strategic Flood Risk Assessment

Tandridge District Council Level 2 SFRA Potential Garden Community

Summary Tables

Table of Contents Redhill Aerodrome ...... 2 Blindley Heath ...... 8 South Godstone ...... 13

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Redhill Aerodrome

OS Grid 528949, 141956 reference

Area 1384ha At the centre of the study area is Redhill Aerodrome. This study area is home to a business park and provides charter flights and flying training.

In the west of the area are the settlements of South Earlswood, White Bushes, Current land use and the edge of Redhill. East Surrey Hospital also occupies a large area. In Catchment the north east is the village of South Nutfield. details Elsewhere the study area is rural consisting of farmland; a mix of arable and grassland.

The topography of the study area is dominated by the wide shallow valleys containing Salfords Stream and Redhill Brook. The flat land at the confluence Topography of these two rivers houses Redhill Aerodrome.

Higher ground is found to the north (105m) and to the south (96m) compared to 55-65m along the valley bottoms.

Redhill Brook flows from the north west edge of the area and is joined by Nutfield Brook from the east. Salfords Stream flows from the east to the south west of the area and is joined by Redhill Brook from the north. Existing watercourses Earlswood Brook flows east to west from the east of the hospital site.

Several ordinary watercourses join both Redhill Brook and Salfords Stream along their length.

The EA Historic Flood Map records a number of flood incidents within the study area:

1968 – The land where Coopers Hill Road crosses Salfords Stream, where Kings Cross Lane crosses Nutfield Brook, the confluence between Redhill Brook and Salfords Stream, Redhill Brook as it passes through Earlswood, Sources of Earlswood Brook at the north of South Earlswood, and Salfords Stream close flood risk to Salfords.

1990 – Salfords Stream at Salfords

Flood history 1993 – Nutfield Brook at South Nutfield and Salfords Stream at Mount Pleasant (by M23) and at Salfords.

2013/14 – Earlswood Brook north of South Earlswood, Redhill Brook north of confluence with Salfords Stream, and Salfords Stream at Brighton Road.

Internal property flooding from surface water has been recorded along Horley Road, Maple Road and Heston Walk at South Earlswood, Cricket Hill, The Avenue and Mid Street at South Nutfield, and Copsleigh Avenue at Salfords.

Several roads are recorded on the Surrey “wetspots” database, Kings Mill Lane close to the aerodrome site, and Clay Lane, west of South Nutfield.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Redhill Aerodrome

Proportion of catchment at risk in Flood Zones FZ3b FZ3a FZ2 FZ1 3.4% 10.7% 12.1% 87.9% Available modelled data: Redhill Brook and Salfords Stream Model (Environment Agency, 2014) covers the main river watercourses flowing across the study area.

Flood characteristics: Salfords Stream has a relatively large flood plain in the east of the area up to the confluence with Redhill Brook, after which point the flood plain narrows. This is mostly on agricultural land. Fluvial

Several properties within South Nutfield are within Flood Zone 2, and an area of Flood Zone 3b (functional flood plain) is present in a green space within a housing area.

Redhill Brook has a relatively large flood plain, but within the study area is mostly on agricultural land. The point where Kings Mill Lane crosses Redhill Brook is within a large area of functional flood plain.

Areas of South Earlswood and Whitebushes lie within the functional flood plain of Earlswood Brook to the south and west of the hospital.

Proportion of catchment at risk (RoFSW) 30-year 100-year 1,000-year 6.0% 9.5% 19.8% Description of surface water flow paths: The study area shows potential for significant ponding of surface water in the vicinity of the Redhill Brook – Salfords Stream confluence, and along both watercourses during a 1 in 30-year (3.3% AEP) rainfall event and greater Surface Water return periods.

A flow path crosses the study area of the aerodrome buildings, with ponding possible in a 1 in 30-year event. Areas of isolated ponding may also occur in the wooded area west of Masons Bridge Road.

Elsewhere flow paths are associated with ordinary watercourses or follow the natural topography.

Areas Susceptible to Groundwater Flooding Map class (risk of groundwater emergence)

The majority of the study area (98%) lies within an area of negligible Groundwater groundwater flood risk. There are two isolated areas in the centre of the study area, one where there is a risk of flooding to subsurface assets but surface manifestation of groundwater is unlikely, and another where groundwater is at or close to the surface and may emerge at significant rates causing risk to both surface and subsurface assets. Reservoir No part of the catchment is at risk from reservoir flooding.

Canal No canals are located within the catchment.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Redhill Aerodrome

Defence Type Standard of Protection Condition Defences The site does not receive protection from flood defences. Salfords Stream passes through three bridges (Coopers Hill Road, M23, Crab Hill Lane) to the east and two to the west (Masons Bridge Road and Brighton Road). A short culverted section is also present in the west as it passes under a railway line. Redhill Brook is culverted for 400m as it passes under the eastern end of the grassed Culvert / structure runways of the aerodrome. Bridges are also Flood risk blockage? management present at Kings Mill Lane and Oaklands infrastructure Drive to the north. Residual risk Nutfield Brook is culverted for part of its length as it passes through the south of South Nutfield. Earlsfield Brook enters a culvert to the south east of Redhill hospital as it passes under Whitebushes. Impounded water body The catchment is not at risk of inundation in failure? the event of reservoir failure. Breach Zone Defence breach / overtopping? The study area is not at risk from breach of defences. The study area contains areas within the Redhill Brook flood alert area, and the “Redhill Brook at Redhill” flood warning area following the course of the brook. To the south of the study area is the Salfords Stream flood alert area and Flood warning “Salfords Stream at Salfords” flood warning area.

Environment Agency flood warnings are now issued to individuals via the Flood Information Service. Access and egress to this area may be constrained by the presence of railway lines to the north and west of the study area, and the M23 to the east which limit the number of access points. Access may be achieved via the A23 from the east (via East Surrey Hospital), however both Masons Bridge Road and Emergency Royal Earlswood Road have a significant surface water flood risk in a 1 in 30- planning year event. The southern end of Masons Bridge Road also crosses Salfords Stream so could be at risk in a 1 in 30-year fluvial event.

Infrastructure Access from the north of the area must cross Redhill Brook, and from the south, Salfords Stream.

Safest access may be from the north west of the area from Earlswood, avoiding the fluvial flood risk from Redhill Brook, and surface water risk north of the hospital site.

Careful consideration of safe access and egress from this area needs to be considered to mitigate the flood risk at access points. River Basin District Central Higher Upper Climate change Central End allowances for ‘2080s’ Thames 25% 35% 70% Climate Change Climate change is unlikely to significantly change the Flood Zone classification Implications for within the area. Some extension of Flood Zone 3a along the length of Redhill the site Brook, on Salfords Stream to the east of the M23 and Earlswood Brook south west of the hospital may be expected.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Redhill Aerodrome

Wealdon Group, (mudstone, siltstone and sandstone) is the dominant bedrock Bedrock for the majority of the area. The most northerly part of the area has bedrock Geology consisting of Lower Greensand group (Sandstone and Mudstone).

Superficial No superficial deposits are known to exist within the study area. Geology

The study area has slowly permeable seasonally wet slightly acid but base-rich Soils loamy and clayey soils with impeded drainage.

SuDS offer opportunities to manage surface water on a development site to reduce the likelihood of a site contributing to flooding elsewhere. They can also offer additional benefits of increasing biodiversity, offering amenity spaces, and the moderation of microclimate. Early design of SuDS is key to maximising those benefits.

The limited permeability of the soils in this location suggests that surface infiltration systems may not be appropriate, however as the underlying geology is permeable deeper infiltration may well be possible. As large parts of this location are currently undeveloped it should be possible to implement other Requirement SuDS features and designs to maximise the infiltration potential of the study for drainage area. control and impact SuDS Source control schemes such as rainwater harvesting should be employed to mitigation reduce runoff leaving sites.

All major developments should include provision for sustainable drainage systems (Planning Practice Guidance (PPG) paragraph 051).

Further information on SuDS is available in the CIRA SuDS Manual (2015) and on the Surrey County Council website, including guidance for developers and planners on integrating SuDS as part of master planning.

http://www.susdrain.org/files/resources/other- guidance/water_people_places_guidance_for_master_planning_sustainable_d rainage_into_developments.pdf

Groundwater Source The area is not located within a Groundwater Source Protection Zone. Protection Zone An area designated as a historic landfill site is located south of Salfords and Historic Landfill north of Axes Lane (Dairy House Farm). This was last used in 1990. In the Site southern part of the study area is a further site (Woolborough Brickworks), last used in 1976.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Redhill Aerodrome

Opportunities for using source control SuDS to manage runoff rates and volumes, contributing to the reduction of flood peaks downstream and existing surface water flow paths leaving the study area.

A greenfield development site is likely to increase the impermeable area within the catchment reducing opportunities for water to infiltrate the ground and increasing the volume and speed that surface water may leave the site, Opportunities for contributing to an increase in flood risk elsewhere. flood risk betterment Major developments (those with 10 or more homes) are expected to integrate SuDS unless demonstrated to be inappropriate.

Both Salfords Stream and Earlswood Brook join the River Mole 1.5-2km west of the study area. There is a potential for increased runoff from within the study Downstream area due to development contributing to flood risk downstream on the River flood risk Mole.

Sequential Test and Exception Test requirements The Sequential Test must be passed. Only once the Sequential Test is passed should the Exception Test be applied. It is expected that all built development will be sequentially located within Flood Zone 1, but the Exception Test would be required: • If More Vulnerable and Essential Infrastructure is located in FZ3a. • If Highly Vulnerable development is located in FZ2 or Flood Zone 3a plus climate change. • If Essential Infrastructure is located in Flood Zone 3b Development will not be permitted in the following scenarios: • Highly Vulnerable development within FZ3a or Flood Zone 3a plus climate change and FZ3b. • More Vulnerable and Less Vulnerable development within FZ3b. Recommendations for requirements of site-specific Flood Risk Assessment, including guidance for developers Recommend- Flood risk assessment: ations for • At the planning application stage, a site-specific flood risk assessment (considering all Local Plan sources of flooding) and surface water drainage strategy will be required. policy • Consultation with the Local Authority and the Environment Agency should be undertaken at an early stage. • Detailed modelling will be required to confirm Flood Zone and climate change extents. The Environment Agency and LLFA should be consulted to obtain the latest hydraulic modelling information for the site at the time of the flood risk assessment. They will advise as to whether existing detailed models need to be updated. • Climate change modelling should be undertaken using the relevant allowances (February 2016) for the type of development and level of risk.

Guidance for site design and making development safe: • Development must seek opportunities to reduce overall level of flood risk at the site. • The development should be designed using a sequential approach. Flood Zones 2 and 3, and 3a + upper end climate change (subject to a detailed flood risk assessment) should be preserved as public green space, with built development restricted to Flood Zone 1. • Safe access and egress should be demonstrated in the 1 in 100 plus climate change event. • Compensation storage would need to be provided for any land-raising within the 1 in 100 plus appropriate climate change flood extent

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Redhill Aerodrome

• Existing surface water flow paths should be retained and incorporated within the site design. • Onsite attenuation options would need to be tested to ensure that altering the timing of peak flows leaving the site does not exacerbate flooding downstream. • All development should adopt source control SuDS techniques to reduce the risk of flooding due to post-development runoff. SuDS design should follow current best practice (CIRIA Manual, 2015) and SCC guidance on runoff rates and volumes, to deliver multiple benefits including water quality, biodiversity, amenity, green infrastructure etc.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Blindley Heath

OS Grid 535807 145264 reference

Area 596ha Catchment This location is rural with a village, and numerous small farms. Aerial details Current land use photography shows the agricultural land is predominantly grassland. The study area consists of higher ground (85m) to the north west and lower Topography (48m) flat ground in the south east which forms the valley of the Ray Brook flows.

Ray Brook crosses west to east at the southern end of the area. The northern end has an un-named ordinary watercourse that joins Ray Brook to the east of Existing the study area where Ray Brook becomes the Eden Brook. Other small watercourses ordinary watercourses as well as drainage ditches are also present on the study area.

The EA Historic Flood Map records a number of flood incidents within the study area:

1960 – Ray Brook 1968 – Ray Brook (more widespread) 2013 – Ray Brook - south east of study area

Flood history Internal property flooding from surface water has been recorded along Crockers Lane, an un-named road off Eastbourne Road (south of cricket pitch) and Maplewood Drive.

Sources of Most of the roads within the study area reported flood incidents along their flood risk length in the winter of 2013/14.

Proportion of catchment at risk in Flood Zones FZ3b FZ3a FZ2 FZ1 0.4% 13.1% 22.9% 77.1% Available modelled data: Medway Model (Environment Agency, 2017) covers the main river watercourses flowing across the study area. Fluvial

Flood characteristics: A large part of the south east of the area is covered by Flood Zone 3a associated with Ray Brook. There are also two areas in the south east between the A22 and B2029 classified as Flood Zone 3b (functional flood plain).

Proportion of catchment at risk (RoFSW) Surface Water 30-year 100-year 1,000-year 5.8% 10.9% 27.4%

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Blindley Heath

Description of surface water flow paths: Primary surface water flow paths indicated on the RoFSW map follow the existing watercourses within the study area in the 1 in 30-year or greater return period event. Additional flow paths may be present in the centre of the area following the natural topography and joining Ray Brook from the north, and from the north east across the B2029.

Areas Susceptible to Groundwater Flooding Map class (risk of groundwater emergence) Groundwater There is a negligible risk of groundwater flooding within the study area.

Reservoir No part of the catchment is risk from reservoir flooding.

Canal No canals are located within the catchment.

Defence Type Standard of Protection Condition Defences The study area does not receive protection from flood defences.

Ray Brook passes under bridges in the south west under Brickhouse Lane, and under the Flood risk Culvert / structure A22 south of Blindley Heath. management blockage? infrastructure No other bridges or culverts are identified in Residual risk the study area. Impounded water body The catchment is not at risk of inundation in failure? the event of reservoir failure. Breach Zone Defence breach / overtopping? The study area is not at risk from breach of defences. The area around Ray Brook and the ordinary watercourse in the north east of the area are within the Rivers Eden and Eden Brook Flood Alert Area, and the Rivers Eden & Eden Brook from Crowhurst and Blindley Heath to Penshurst Flood warning Flood Warning Area.

Emergency Environment Agency flood warnings are now issued to individuals via the Flood planning Information Service. The A22 runs north-south through the eastern part of this area. This road has eperienced flooding from surface water and from Ray Brook in the winter of Infrastructure 2013/14.

Other minor roads in the area also have a history of flooding. River Basin District Central Higher Upper Climate change Central End allowances for ‘2080s’ Thames 25% 35% 70% Climate Change Implications for Climate change is likely to increase the extent of Flood Zone 3a in the south the site east of the area.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Blindley Heath

Bedrock Wealdon Group, (mudstone, siltstone and sandstone) Geology

Superficial No superficial deposits are known to exist within the study area Geology

The area has slowly permeable seasonally wet slightly acid but base-rich Soils loamy and clayey soils with impeded drainage.

The nature of the soils across most of the catchment may limit opportunities for infiltration SuDS schemes, but many other options could be implemented Requirement successfully. for drainage control and SuDS impact All major developments should include provision for sustainable drainage mitigation systems (Planning Practice Guidance (PPG) paragraph 051).

http://www.susdrain.org/files/resources/other- guidance/water_people_places_guidance_for_master_planning_sustainable_d rainage_into_developments.pdf

Groundwater Source The area is not located within a Groundwater Source Protection Zone. Protection Zone Six areas designated as historic landfill sites exist within the study area. Historic Landfill Pet Cemetary at Upper Barn Farm, Field at Churchill Stud (west of Blindley Site Heath), Heath View and Heath Farm (to the east of Blindley Heath), Stanton Hall Harm and land adjacent to Crockers Lane (by the A22).

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Blindley Heath

Opportunities for using source control SuDS to manage runoff rates and volumes, contributing to the reduction of flood peaks downstream and existing surface water flow paths leaving the site.

betterment Major developments (those with 10 or more homes) are expected to integrate SuDS unless demonstrated to be inappropriate.

Ray Brook, and the ordinary watercourse in the north of the area flow into the River Eden which passes through Edenbridge to the east. The extent of Flood Downstream Zone 3a covers part of the southern side of this town. An increase in discharge flood risk into either of the watercourses could exacerbate an existing flood risk in this area. Sequential Test and Exception Test requirements The Sequential Test must be passed. Only once the Sequential Test is passed should the Exception Test be applied. It is expected that all built development will be sequentially located within Flood Zone 1, but the Exception Test would be required: • If More Vulnerable and Essential Infrastructure is located in FZ3a. • If Highly Vulnerable development is located in FZ2 or Flood Zone 3a plus climate change. • If Essential Infrastructure is located in Flood Zone 3b Development will not be permitted in the following scenarios: • Highly Vulnerable development within FZ3a or Flood Zone 3a plus climate change and FZ3b. • More Vulnerable and Less Vulnerable development within FZ3b. Recommendations for requirements of site-specific Flood Risk Assessment, including guidance for developers Recommend- Flood risk assessment: ations for • At the planning application stage, a site-specific flood risk assessment (considering all Local Plan sources of flooding) and surface water drainage strategy will be required. policy • Consultation with the Local Authority and the Environment Agency should be undertaken at an early stage. • Detailed modelling will be required to confirm Flood Zone and climate change extents. The Environment Agency and LLFA should be consulted to obtain the latest hydraulic modelling information for the site at the time of the flood risk assessment. They will advise as to whether existing detailed models need to be updated. • Climate change modelling should be undertaken using the relevant allowances (February 2016) for the type of development and level of risk.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name Blindley Heath

plus appropriate climate change flood extent • Existing surface water flow paths should be retained and incorporated within the site design. • Onsite attenuation options would need to be tested to ensure that altering the timing of peak flows leaving the site does not exacerbate flooding downstream. • All development should adopt source control SuDS techniques to reduce the risk of flooding due to post-development runoff. SuDS design should follow current best practice (CIRIA Manual, 2015) and SCC guidance on runoff rates and volumes, to deliver multiple benefits including water quality, biodiversity, amenity, green infrastructure etc.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name South Godstone

OS Grid 536922 148558 reference

Area 1384ha

Catchment The study area is mostly rural, but includes the village of South Godstone. details Current land use Agriculture is a mix of grassland and arable.

There is high ground in the north west of the study area (160m), the land then Topography falls away steeply and the central and south eastern areas are fairly flat (60- 70m). Gibbs Brook flows across the north east of the area towards the south east where it joins the River Eden just outside the area.

Existing Country Stream is present in the south east and joins the River Eden 1km watercourses further downstream than Gibbs Brook.

An un-named ordinary watercourse flows through the south west corner of the study area and joins Ray Brook. The EA Historic Flood Map records a number of flood incidents within the study area:

In the south of the area, the ordinary watercourse experienced flooding in 1960 and again in 1968. More widespread flooding was experienced on Gibbs Brook in 1968. Flood history Internal property flooding is known to have occurred along the A22, south of South Godstone and on Water Lane linking the A22 with Tilburstow Hill Road. External property flooding and highway flooding has been recorded at several points along the A22 and Tandridge Lane which both cross north-south through the study area. Sources of

flood risk Proportion of catchment at risk in Flood Zones FZ3b FZ3a FZ2 FZ1 0% 2.7% 5.0% 95.0% Available modelled data: The catchment is not covered by any modelled extents.

Flood characteristics: Fluvial

The flat land in the north east corner leads to a wide flood plain for Gibbs Brook.

The ordinary watercourse in the south has a narrower flood plain. Country Stream has a prominent area of Flood Zone 2 associated with a historic flood close to the A22.

Proportion of catchment at risk (RoFSW) Surface Water 30-year 100-year 1,000-year 5.1% 7.8% 17.1%

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name South Godstone

Description of surface water flow paths:

In the north of the area surface water flow paths correspond to existing watercourses (Gibbs Brook and tributaries). The most significant area of ponding is east of Tandridge Lane where a wide area may experience flooding in a 1 in 30-year or greater return period event.

Along Country Stream, a significant area of ponding may occur where the surface water flow path is interrupted by the railway line and in the south east of the area to the west of Tandridge Lane.

In the south east of the area, flow paths draining to the ordinary watercourse exist, as well as areas of ponding as the flow paths cross Tilburstow Hill Road.

Areas Susceptible to Groundwater Flooding Map class (risk of groundwater emergence)

In the south of the area is a band of higher groundwater risk where there is a risk of groundwater flooding to surface and subsurface assets. There is a possibility of groundwater emerging at the surface locally. In part of this region, groundwater may emerge at significant rates and has the capacity to flow overland and/or pond within any topographic low spots. This corresponds to Groundwater an area where the bedrock geology changes to interbedded sandstone and mudstone.

In the north of the area where the bedrock is Lower Greensand group, another area of higher groundwater flood risk (same classification as above) exists.

The remaining parts of the study area (90%) lie within an area of negligible groundwater flood risk.

Gibbs Brook (east of Tandridge Lane) is at risk of from reservoir flooding Reservoir (Bough Beach, and Wilderness Lake) Canal No canals are located within the catchment.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name South Godstone

Defence Type Standard of Protection Condition Defences The study area does not receive protection from flood defences.

Gibbs Brook flows under bridges at New Road, Tandridge Lane and Gibbs Brook Lane.

Country Stream flows under Tandridge Lane, and under an unnamed road between Tandridge Lane and Crowhurst Lane. Flood risk Culvert / structure management blockage? The ordinary watercourse in the south of the infrastructure area flows under a bridge at Tilburstow Hill Road before flowing under the A22 and Residual risk Danemore Lane.

No culverts were apparent during a map survey.

Gibbs Brook (east of Tandridge Lane) is at Impounded water body risk of from reservoir flooding (Bough Beach, failure? and Wilderness Lake) Breach Zone Defence breach / overtopping? The study area is not at risk from breach of defences. All three of the watercourses are included in the “Rivers Eden and Eden Brook” Flood Alert Area. The ordinary watercourse at the southern side of the study area within the Rivers Eden & Eden Brook from Crowhurst and Blindley Heath Flood warning to Penshurst” Flood Warning Area.

Environment Agency flood warnings are now issued to individuals via the Flood Emergency Information Service. planning The A22 runs north-south through the middle of the study area and is bisected by railway line running east-west.

Infrastructure The A22 has experienced flooding from surface water at multiple points along its length.

River Basin District Central Higher Upper Climate change Central End allowances for ‘2080s’ Thames 25% 35% 70% Climate Change Climate change may increase the extent of Flood Zone 3a on all three of the Implications for watercourses in the study area, in particular in the south east of the area by the site Tandridge Lane.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name South Godstone

The majority of the study area has bedrock consisting of Wealden Group - mudstone, siltstone and sandstone.

Bedrock There is a band through the southern part of the area of Sandstone and Geology Siltstone interbedded (also Wealden Group).

In the north of the study area the bedrock is Lower Greensand Group – sandstone and mudstone.

Superficial No superficial deposits are known to exist in the study area. Geology

The study area has slowly permeable seasonally wet slightly acid but base-rich Soils loamy and clayey soils with impeded drainage.

the moderation of microclimate. Early design of SuDS is key to maximising Requirement those benefits. for drainage control and The nature of the soils across most of the catchment may limit opportunities for impact infiltration SuDS schemes, but many other options could be implemented mitigation successfully.

SuDS All major developments should include provision for sustainable drainage systems (Planning Practice Guidance (PPG) paragraph 051).

http://www.susdrain.org/files/resources/other- guidance/water_people_places_guidance_for_master_planning_sustainable_d rainage_into_developments.pdf

Groundwater The northern part of the area is located within a Groundwater Source Source Protection Zone (Zone 3 – Total Catchment). Protection Zone Areas designated as a historic landfill sites are located to the south of the railway line at the western edge of the study area (Lambs Brickworks), north of Historic Landfill the railway line at South Godstone (Old Hall Farm), south of the railway line on Site the western edge of the study area, at two sites each side of the A22 north of South Godstone and in the north of the study area (Taylors Hill Sandpit).

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name South Godstone

Opportunities for using source control SuDS to manage runoff rates and volumes, contributing to the reduction of flood peaks downstream and existing surface water flow paths leaving the site.

Detailed modelling of the Upper River Eden and Gibbs Brook to better understand fluvial flood risk in this study area.

A greenfield development site is likely to increase the impermeable area within Opportunities for the catchment reducing opportunities for water to infiltrate the ground and flood risk increasing the volume and speed that surface water may leave the site, betterment contributing to an increase in flood risk elsewhere.

Major developments (those with 10 or more homes) are expected to integrate SuDS unless demonstrated to be inappropriate.

Small development sites, infill, or windfall sites may not individually contribute a significant volume to runoff, but taken cumulatively, could contribute to an increase in flood risk if not managed appropriately. SuDS design options are available for smaller sites. Gibbs Brook and the ordinary watercourse in the south of the area flow into the River Eden which passes through Edenbridge to the east. The extent of Flood Downstream Zone 3a covers part of the southern side of this town. An increase in discharge flood risk into either of the watercourses could exacerbate an existing flood risk in this area. Sequential Test and Exception Test requirements The Sequential Test must be passed. Only once the Sequential Test is passed should the Exception Test be applied. It is expected that all built development will be sequentially located within Flood Zone 1, but the Exception Test would be required: • If More Vulnerable and Essential Infrastructure is located in FZ3a. • If Highly Vulnerable development is located in FZ2 or Flood Zone 3a plus climate change. • If Essential Infrastructure is located in Flood Zone 3b Development will not be permitted in the following scenarios: • Highly Vulnerable development within FZ3a or Flood Zone 3a plus climate change and FZ3b. • More Vulnerable and Less Vulnerable development within FZ3b. Recommendations for requirements of site-specific Flood Risk Assessment, including Recommend- guidance for developers ations for Flood risk assessment: Local Plan • At the planning application stage, a site-specific flood risk assessment (considering all policy sources of flooding) and surface water drainage strategy will be required. • Consultation with the Local Authority and the Environment Agency should be undertaken at an early stage. • Detailed modelling will be required to confirm Flood Zone and climate change extents. The Environment Agency and LLFA should be consulted to obtain the latest hydraulic modelling information for the site at the time of the flood risk assessment. They will advise as to whether existing detailed models need to be updated. • Climate change modelling should be undertaken using the relevant allowances (February 2016) for the type of development and level of risk.

Tandridge District Council

Level 2 SFRA Detailed Site Summary Tables

Area name South Godstone

• Safe access and egress should be demonstrated in the 1 in 100 plus climate change event. • Compensation storage would need to be provided for any land-raising within the 1 in 100 plus appropriate climate change flood extent • Existing surface water flow paths should be retained and incorporated within the site design. • Onsite attenuation options would need to be tested to ensure that altering the timing of peak flows leaving the site does not exacerbate flooding downstream. • All development should adopt source control SuDS techniques to reduce the risk of flooding due to post-development runoff. SuDS design should follow current best practice (CIRIA Manual, 2015) and SCC guidance on runoff rates and volumes, to deliver multiple benefits including water quality, biodiversity, amenity, green infrastructure etc.