Home > Flood risk > Flood risk is an issue in both strategic locations

Flood risk is an issue in both strategic locations


Flood risk is an issue in both strategic locations. The Strategic Flood Risk Assessment (February 2008 by Capita Symonds) has raised a number of concerns. It says:

North Angmering

Rivers

Mostly low probability (Flood Zone 1). Not expected to be flooded from rivers in 2056 or 2106 climate change time-horizons.

Sea

Mostly low probability (Flood Zone 1). Not expected to be flooded from sea in 2056 or 2106 climate change time-horizons.

Land

Medium probability of surface water flooding. No recorded historic incidents of flooding at site. However several recorded incidents of flooding in the vicinity.

Groundwater

High potential for groundwater flooding. Located in a groundwater emergence zone (Defra 2004). However no recorded incidents of groundwater flooding.

Sewers

Medium probability of flooding from sewers. Likely to be limited existing sewer infrastructure at the site although some recorded incidents of sewer flooding in the vicinity.

Possible Strategic Solutions

None identified. Strategic solutions are unlikely to reduce groundwater flood risk. Site specific measures required.

Requirements of FRA

FRA to assess management surface water runoff is required for sites larger than 1ha. Surface water runoff will need to be maintained at existing levels. Groundwater flooding to be considered further. Exception Test may be required for “more vulnerable” development located in areas where probability of groundwater flooding is considered high.

Surface Water Management

Land is generally greenfield therefore development of the site is likely to lead to increased runoff. Surface water runoff will need to be restricted to the existing rates. A strategic surface water management scheme may be feasible. Soils and geology information indicate the land is relatively permeable. Soakaways / infiltration may be effective and should be considered in preference to attenuation and storage of runoff.

South Angmering

Rivers

Low probability (Flood Zone 1). Not expected to be flooded from rivers in 2056 or 2106 climate change time-horizons.

Sea

Low probability (Flood Zone 1). Not expected to be flooded from sea in 2056 or 2106 climate change time-horizons.

Land

Medium probability of surface water flooding. Some recorded incidents of surface water flooding in the site and vicinity.

Groundwater

High potential for groundwater flooding. Located in a groundwater emergence zone (Defra 2004). However no recorded incidents of groundwater flooding.

Sewers

Medium probability of flooding from sewers. Some recorded incidents in the site and vicinity.

Possible Strategic Solutions

None identified. Strategic solutions are unlikely to reduce groundwater flood risk. Site specific measures required.

Requirements of FRA

FRA to assess management of surface water runoff is required for sites larger than 1ha. Surface water runoff will need to be maintained at existing levels. Groundwater flooding to be considered further. Exception Test may be required for “more vulnerable” development located in areas where probability of groundwater flooding is considered high.

Surface Water Management

Land is generally greenfield therefore development of the site is likely to lead to increased runoff. Surface water runoff will need to be restricted to the existing rates. A strategic surface water management scheme may be feasible. Soils and geology information indicate the land is relatively permeable. Soakaways / infiltration may be effective and should be considered in preference to attenuation and storage of runoff.

Westergate (includes Eastergate)

Rivers

Mostly low probability (Flood Zone 1). Not expected to be flooded in 2056 or 2106 climate-change time horizons. Land immediately adjacent to the watercourses is functional floodplain (Flood Zone 3b). No significant change in flooding for 2056 or 2106 climate change time-horizons. Accuracy of flood outline should be considered when making land use planning decisions.

Sea

Mostly low probability (Flood Zone 1). Not expected to be flooded in 2056 or 2106 climate change time horizons. Land immediately adjacent to the watercourses is high probability (Flood Zone 3). Existing flood defences prevent flooding from the sea at the site. Not expected to be flooded in 2056 or 2106 climate change time-horizons (assuming existing defences remain). Accuracy of flood outline should be considered when making land use planning decisions

Land

Medium to high risk of flooding from land. Underlying soil and geology prone to surface water flooding. Site is on flat land and many drainage channels cross the site. Several recorded incidents of historic surface water flooding at the site.

Groundwater

Medium potential for groundwater flooding however no recorded incidents of flooding.

Sewers

Medium risk of flooding from sewers. Recorded incidents of sewer flooding in existing villages.

Possible Strategic Solutions

Improvements to existing surface water drainage may reduce flood risk.

Requirements of FRA

Further assessment of flooding from land and groundwater required. Assessment of management of surface water runoff is required for sites larger than 1ha. Surface water runoff will need to be maintained at existing levels. Revisit Flood Zones to ensure suitably accurate for land use planning decisions. Maintenance of existing flood defences and likely standard of protection provided in the future should be considered. Sequential approach recommended with “more vulnerable” development land-uses located away from the watercourses. Exception Test may be required if “more vulnerable” development is placed in areas where the probability of flooding (from any source) is considered high.

Surface Water Management

Land is generally Greenfield therefore development of the site is likely to lead to increased runoff. The existing sewer system is unlikely to have spare capacity. Surface water runoff will need to be restricted to the existing rates. Soils and geology information indicate the land is relatively impermeable. Soakaways / infiltration devices unlikely to be effective therefore storage systems likely to be required to restrict runoff.

Barnham

Rivers

Mostly low probability (Flood Zone 1). Not expected to be flooded in 2056 or 2106 climate-change time horizons. Land immediately adjacent to the watercourses is functional floodplain (Flood Zone 3b). No significant change in flooding for 2056 or 2106 climate change time-horizons. Accuracy of flood outline should be considered when making land use planning decision.

Sea

Mostly low probability (Flood Zone 1). Not expected to be flooded in 2056 or 2106 climate change time horizons. Land immediately adjacent to the watercourses and in the south of the site high probability (Flood Zone 3). Existing flood defences prevent flooding from the sea at the site. Not expected to be flooded in 2056 or 2106 climate change time-horizons (assuming existing defences remain). Accuracy of flood outline should be considered when making land use planning decision.

Land

Medium to high probability of flooding from land. Underlying soil and geology prone to surface water flooding. Site is on flat land and many drainage channels cross the site. Many recorded incidents of historic surface water flooding in the vicinity of the site. Area is known to suffer from surface water flooding.

Groundwater

Medium to high potential for groundwater flooding however no recorded incidents of flooding.

Sewers

Medium probability of flooding from sewers. Recorded incidents of sewer flooding in existing villages. Sewer pumping stations located in the vicinity.

Possible Strategic Solutions

Improvements to existing surface water drainage may reduce flood risk.

Requirements of FRA

Further assessment of flooding from land and groundwater required. Assessment of management of surface water runoff is required for sites larger than 1ha. Surface water runoff will need to be maintained at existing levels. Revisit Flood Zones to ensure suitably accurate for land use planning decisions. Maintenance of existing flood defences and likely standard of protection provided in the future should be considered. Sequential approach recommended with “more vulnerable” development located away from the watercourses. Exception Test may be required if “more vulnerable” development is placed in areas where the probability of flooding (from any source) is considered high.

Surface Water Management

Land is generally Greenfield therefore development of the site is likely to lead to increased runoff. The existing sewer system is unlikely to have spare capacity. Surface water runoff will need to be restricted to the existing rates. Soils and geology information indicate the land is relatively impermeable. Soakaways / infiltration devices unlikely to be effective therefore storage systems likely to be required to restrict runoff.

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  1. July 11, 2012 at 7:14 pm

    ………. and I thought you were only 21.

    Unfortunately, planners have little or no interest in local knowledge. But they can’t ignore actual hard evidence. Does anyone have any photographs of the flooding from either 2000 or 2012. If so, we can post them on this blog.

  2. John Penfold
    July 11, 2012 at 5:57 pm

    I may not be a planner,but I have lived in these villages all my 73 years and my family has farmed this coastal plain from Worthing to Bognor since the 1700’s.
    I have known many practical wise men of the past who either farmed here or worked for the old Sussex River Authority and Water Companies who have told me how drainage works in this area.
    Today’s “experts” are theorists with no local knowledge using computer models,they are usually townies from outside working for Consultants who are only interested in giving their client the answers they want to permit huge new developments on totally greenfield sites.
    I suggest every one should read the blog above #4, I said this in the response to the old Local Plan,all that has happened since is that we have had more large developments and more heavy rainfall and flooding.
    It is no excuse to pretend this is one-off monsoon weather,it is Climate Change,however it is caused.
    If Planners ignore it,there will be continuing misery for residents within and to the South of the Five Villages.
    John Penfold

  3. June 23, 2012 at 6:21 am

    ………… and in the June 2012 floods did the council’s planning officers take the opportunity to make an assessment of flooding in the strategic locations? If so, will they make that information public? If not, why not?

  4. June 18, 2012 at 10:10 pm

    I agree, but hey their answer to us would be “YOU ARE NOT PLANNERS”,

  5. June 18, 2012 at 8:29 pm

    Eastergate, Westergate and Barnham all suffer badly with flooding. The land is very flat and there is almost no fall between these villages and the coast. Water simply sits on the land or roads and only drains away very slowly. The water table is very high.

    Rainwater is stored in aquifers in the Downs, but the excess always flows south towards the sea via streams and rifes (small rivers) and underground in shifting sand strata (known as green sand). This underground flow has been altered by the gravel extraction around Chichester. The gravel pits, which are full of water, actually divert the ground water towards Eastergate, Westergate and Barnham . This increases as the water flow grows, so lifting the water table east of the gravel pits.

    New development will add to the problem by providing increased catchment areas of roofs, roads and other hard standings, whilst by reducing agricultural land, field percolation will also be reduced.

    The rifes are inadequate and clearly do not have the capacity to cope at certain times. The result is overloaded drainage, floods and overwhelmed sewage plants.

    In the floods of 2000 three of the four routes into Westergate were impassable. In 2012 the A29 was closed at Shripney – again.

    The Fontwell Avenue pumping station could not control the capacity of the extra water flow in 2000 and it was left ‘open’ to run into the villages via the A29 and the stream that crosses near Elm Tree Stores.

    The “hill” created by the landfill at Lidsey is capped with clay to contain toxins etc. and thereby to stop them leaching into the topsoil. If this works as intended it also means that rainwater cannot penetrate the clay from the outside either, so instead of normal field percolation rainwater will instead run off the “hill”.

    With the “hill” covering a large acreage, water will run off at speed in all directions and will substantially increase the risk of flooding in any new development nearby.

    This will also increase the risk of flooding at Bersted and Felpham.

  6. Mike Turner (Villages Action Group)
    June 18, 2012 at 4:48 pm

    I absolutely agree with the comments about the need to change the calculation from 100 years to 5/10 years due to the massive climate change we are now experiencing, for whatever cause. This is now a whole new ball game and Councils and developers had better start recognising the fact before insurance companies start refusing to insure all the new houses that they would like to build.

  7. June 18, 2012 at 12:58 pm

    Westergate is part of Aldingbourne Parish, and therefore Aldingbourne has a flood risk, both from surface and sewage. Recent rainfall sewerage and surface water flooded fields in Aldingbourne and Woodgate areas, EA actually inspected these and are going to write to Southern Water regarding cleaning up and doing something to alleviate the problem. Lydsey Pumping station cannot cope with any more housing being built in any of the 5 villages. The more concrete that is laid the more flooding we will all get. Climate change may be the cause of this therefore the old adage of every 100 years should be forgot and replaced with every 5/10 years.

  8. Barbara Alcock
    June 10, 2012 at 6:03 pm

    Great idea to share the information in this way – thank you.

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