Proposed Residential Development at Holbeach Manor, Fleet Road, Holbeach, Spalding, Pe12 7Ax
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PROPOSED RESIDENTIAL DEVELOPMENT AT HOLBEACH MANOR, FLEET ROAD, HOLBEACH, SPALDING, PE12 7AX. FLOOD RISK ASSESSMENT View of site from south end S M Hemmings B Sc C Eng MICE MIWEM, 13 Lea Gardens, Peterborough, PE3 6BY . This flood risk assessment has been prepared solely to support the planning application for the residential development at Holbeach Manor, Fleet Road, Holbeach. The author has made every effort to provide an accurate assessment of the flood risk but accepts no liability should the information be found to be incorrect or incomplete, or if it is used for any other purposes other than for which it was originally commissioned. 1 Introduction A residential development is proposed east of Holbeach Manor at Fleet Road, Holbeach, Spalding. The land is at present part of the extensive gardens to the property. The site is in Flood Zone 3 as shown on the Environment Agency’s Flood Zone map. The flood zone maps do not take into account existing flood defences. For the Planning Application to be valid a flood risk assessment needs to be carried out to conform with the requirements of the Technical Guidance to the National Planning Policy Framework Development and Flood Risk. The site is within a defended area as specified in the South Holland District Council’s Strategic Flood Risk Assessment and is located in the South Holland Internal Drainage Board District. Environment Agency (EA) Flood Zones The map below is taken from the Environment Agency website and shows the flood zones in the area. It can be seen that all of this area east of Holbeach is within Flood Zone 3. There is a small area in the centre of Holbeach which is higher and is within flood zones 1 and 2. Application Site The development is located on the eastern side of Holbeach. The National Grid Reference of the site is 536760 324680. The location of the site is shown on the plan at the end of this document. Applying the flood risk vulnerability classification in Table 2 of the Guidance, a development consisting of dwelling houses is classified as “more vulnerable”. Table 3 of the Guidance is shown below: 2 Flood Flood Risk Vulnerability Classification Zones Essential Highly vulnerable More vulnerable Less Water infrastructure vulnerable compatible Zone 1 ✓ ✓ ✓ ✓ ✓ Exception Test Zone 2 ✓ ✓ ✓ ✓ required Exception Test Exception Test Zone 3a † ✗ ✓ ✓ required † required Exception Test Zone 3b * ✗ ✗ ✗ ✓* required * Therefore it can be seen that for “More vulnerable” development the sequential and the exception tests need to be applied to the development. Sequential Test The aim of the Sequential Test, as set out in the Planning Practice Guidance, is to ensure that a sequential approach is followed to steer new development to areas with the lowest probability of flooding. The flood zones as defined in the Strategic Flood Risk Assessment for the area provide the basis for applying the Test. The aim is to steer new development to Flood Zone 1 (areas with a low probability of river or sea flooding). Where there are no reasonably available sites in Flood Zone 1, local planning authorities in their decision making should take into account the flood risk vulnerability of land uses and consider reasonably available sites in Flood Zone 2 (areas with a medium probability of river or sea flooding), applying the Exception Test if required. Only where there are no reasonably available sites in Flood Zones 1 or 2 should the suitability of sites in Flood Zone 3 (areas with a high probability of river or sea flooding) be considered, taking into account the flood risk vulnerability of land uses and applying the Exception Test if required. As can be seen from the map on page 2 of this report all of the area on the east side of Holbeach is in Flood Zone 3. Therefore it would be difficult to find a similar site for the development in Holbeach that is in a lower flood risk zone. Most of the areas within Holbeach and Fleet which have been allocated for development and are included within the South East Lincolnshire Local Plan (SELLP) adopted in March 2019 are within flood zone 3(a). A list of the allocated sites in the Holbeach and Fleet area is shown on pages 200 – 203 of the local plan document. The flood hazard and predicted maximum flood depths of these allocated sites are listed on the next page. This information has been taken from the Holbeach section of the South East Lincolnshire Strategic Housing land Availability Assessment. 3 Site Area (ha) Flood Hazard Flood Depth Hob004 5.85 Danger for Some 250mm – 500mm Hob010 0.79 No Hazard No depth Hob032 6.27 No Hazard No depth Hob048 42.2 Low Hazard 250mm – 500mm The assessment for the site at Holbeach Manor is as follows Site Area (ha) Flood Hazard Flood Depth - - Low Hazard 0 – 250mm There are 2 allocated sites with a lower flood hazard than the site at Holbeach Manor and 2 sites that have been allocated with a greater hazard than the site at Holbeach Manor. Sequentially the proposal site has a better predicted flood depth than two of the sites allocated within the latest Local Plan. Site Hob045 situated immediately south of the proposed development site was not allocated in the plan. A planning application for this site (reference H09-0332-16) was approved in 2017. The flood hazard for this site was specified as “danger for most” and the predicted flood depth was between 500mm and 1.0 metre. It can be seen that the hazard and the predicted flood depth is greater than the proposed development site. The safety of the development will be delivered by ensuring the floor levels of the proposed new houses are above the predicted residual flood levels in a 1 in 200 year event in 2115 for this area. The South Holland District Council Core Strategy states that there is a limited number of sites in the South Holland DC area available for residential development. Some further sites will need to be identified to enable the Council to meet the RSS and Structure Plan requirement for 2021. Therefore there is a requirement for further sites to be brought forward and used for residential development. Therefore taking into account the above I consider that the sequential test for this site has been passed. Exception Test The Sequential Test has demonstrated that it is not possible, consistent with wider sustainability objectives, for the development to be located in zones with a lower probability of flooding. Therefore the Exception Test must be applied and for this to be passed: • It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risks, informed by the Strategic Flood Risk Assessment; and 4 • A site-specific flood risk assessment must demonstrate that the development will be safe for its lifetime taking into account of the vulnerability of its users, without increasing flood risk elsewhere, and where possible will reduce flood risk overall. Both parts of this test must be satisfied in order for the development to be considered appropriate in terms of flood risk. There must be robust evidence in support of every part of the test. The first section will be demonstrated by the Supporting Planning Statement and compliance with South Holland District Council’s planning policies. This flood risk assessment will demonstrate that the development will be safe for its lifetime and it will not increase flood risk elsewhere. Strategic Flood Risk Assessment The Strategic Flood Risk Assessment (SFRA) written for the South Holland District Council (SHDC) in 2010 provides details of the actual flood risk in the Council’s area. This information has not been updated and reference to the maps in this document give the following information for the actual flood risk and hazard at the site for the 1% fluvial event and 0.5% tidal event. For the present day Depth of flooding … zero Extent of flooding .. Low or medium flood probability Peak Velocity ……. Nil For year 2115 Depth of flooding … zero Extent of flooding…. Low or medium flood probability Peak Velocity …… Nil The maps showing the residual flood hazard were revised in the 2016 update of the South Holland District Council Strategic Flood Risk Assessment which can be found on the website of the South East Lincolnshire Joint Planning Committee. The residual hazards are as follows for the 1% fluvial or 0.5% tidal event probability: For the present day Depth of flooding …zero Extent of flooding .. Low or medium flood probability Hazard……….. None Peak Velocity .. Nil For the year 2115 Depth of flooding …0 – 500mm Extent of flooding .. High Hazard…………. Low Hazard Peak Velocity .. 0 – 0.3m/sec Figure 16 of the general maps shows that the site is not within the rapid inundation zone. 5 Maximum flood level and bank levels in the River Welland The maximum levels in this tidal section of the River Welland 9.2 km west of the site are as follows: 2007 2115 Peak 1 in 200 year level 5.98 7.12 Peak 1 in 1000 year level 6.27 7.41 The lowest levels of the east bank of the River Welland around chainage 18km are 7.50m OD, with average levels between 7.60m and 7.70m OD. Maximum flood level and bank levels in the River Nene The maximum levels in this tidal section of the River Nene 12.5km east of the site are as follows: 2007 2115 Peak 1 in 200 year level 5.79m OD 6.93m OD Peak 1 in 1000 year level 6.13m OD 7.27m OD The defence level (top of left bank) at chainage between the South Holland Main Drain and the North level Main Drain is between 7.00m and 7.30mOD.