South Essex Surface Water Option Scoring Matrix

SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 1 - Identify Potential Measures

Critical Drainage Area ID: CAS 1 South Benfleet

• Surface water tends to flow from the northwest to the southwest of the CDA, towards Benfleet Marsh where the surface water flood depths are greatest. There is one PSWFH area within the CDA. There is a extensive network of drainage ditches that will convey surface water runoff across the catchment. The steep topography to the Description: east of the CDA generates the relative high flow velocities and flood hazards. • A large proportion of the PSWFH coincides with the Benfleet Hall Sewer tidal and fluvial flood zones 2 and 3. • Surface water ponds within the South Benfleet storage area.

Flood Risk Surface Water, Ordinary Watercourse and Sewer Categorisation: 639 buildings of which 542 are residential properties >0.1m Property Count: 39 buildings of which 25 are residential properties >0.3m 6 buildings of which 2 are residential properties >0.5m • South Benfleet Foundation School, Jotmans Hall School, The Appleton School, Critical Kents School, Holy Family Catholic School. • 5 Pumping Stations Infrastructure: • Police Station • Nursing Home

• Flood records have been recorded at Clifton Way, Grove Road and Avondale Road. The latter two flood locations are in proximity to a drainage ditch. Validation: • Sewer flooding records are at Fernlea Road, Greenwood Avenue and at the junction between Vicarage Hill and High Road.

Pluvial modelling indicates that surface water flows are generated from Thundersley Glen (to the northeast of CDA) and Hill Top Farm (to the southeast of the CDA). Surface water from these areas flows towards the Benfleet Hall Sewer which then PSWFH: converges with a tributary of the Benfleet Brook. These main flow paths follow the topography and fluvial channels through the CDA. The PSWFH encompasses the areas of Vicarage Hill, Grove Road and Saxon Way.

Figure C 19 – Surface Water Flood Depth (1% AEP) Figures: Figure C 20 – Surface Water Flood Hazard (1% AEP) SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 1 - Identify Potential Measures

Critical Drainage Area ID: CAS 1 South Benfleet

Measure Opportunity Assessment Description Location / Specific Details Comments

To be identified on site-by-site basis when opportunities arise but likely to be limited Green Roof opportunity for implementation of measure within a Generic Measure Throughout CDA the CDA. Further investigation is needed to assess the Soakaways a Generic Measure Throughout CDA infiltration potential due to geology. Further investigation is needed to assess the Swales a Generic Measure Throughout CDA infiltration potential due to geology. Further investigation is needed to assess the Permeable Paving a Generic Measure Throughout CDA infiltration potential due to geology.

SOURCE Rainwater Harvesting g Generic Measure Northern residential properties To be identified on site-by-site basis. Create and enhance water Modification of opens spaces to temporarily retain Detention Basins storage spaces in existing green Western extent of Benfleet Marsh, stormwater, either through creation of bunds or g and open spaces Boyce Hill Golf Course excavation. Ponds and wetlands with Would require a permanent water supply, but Ponds and Wetlands additional capacity to could also provide additional social and a accommodate runoff Hope Green environmental benefits. Other 'Source' Measures N/A Increasing Capacity in Drainage Systems G PSWFH Separation of Foul and Surface Water Sewers r Foul and surface sewers already separate Improved Maintenance Regimes G Generic Measure Throughout CDA To be identified on site-by-site basis. Provide additional capacity for flood water along Managing Overland Flows (Online Storage) Increase channel width along water courses. Could be developed to support a sections of channel Hopes Green riparian habitats. Alteration of road structure (increased pavement height and Managing Overland Flows (Preferential Flowpaths) lower road depth) to define flow Divert water to flow down Grove path of surface water Road and Thundersley Park Road.

PATHWAY g Aeration of compact ground on In the north and west of the CDA sports fields. Increased (Thundersley Glen, Badger Hall, Increasing infiltration within the topsoils of the Land Management Practices vegetation coverage. Farming Shipwrights Wood and Boyce Hill sports ground at the head of the catchment will g practices Golf Club). reduce the volume of surface water generated Deculverting Watercourse(s) r Watercourses are already open where possible Other 'Pathway' Measures N/A Employ Extremer Weather Alert Improved Weather Warning service provided by Mett Office Combine with SWMP mapped outputs to inform a and EA Throughout CDA emergency planners of areas to focus resources. Planning Policies to Influence Development G Generic Measure Throughout CDA For all new development. Temporary or Demountable Flood Defences g PSWFH Will be dependent on engagement opportunities with community. Social Change, Education and Awareness g Generic Measure Throughout CDA In areas with a large migration of population it will be difficult to undertake / pass on information from RECEPTOR one property owner to other This could potentially be implemented across a Improved Resilience and Resistance Measures Throughout CDA large proportion of buildings in the CDA and is a unlikely to be cost beneficial. Other 'Receptor' Measures N/A SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 2 and 3 - Optons Identification and Short Listing

Critical Drainage Area ID: CAS 1 South Benfleet

Standard Measures Shortlisting Options SOURCE PATHWAY RECEPTOR ssessment?

Option No. Option (Scheme Category) Comments easures Available? Social Overall Technical Economic Objectives Environmental Forward Option to Detailed A Detailed to Option Forward Appropriate M Appropriate Take Green Roof Soakaways Swales Permeable Paving Rainwater Harvesting Detention Basins Ponds and Wetlands Other 'Source' Measures Increasing Capacity in Drainage Systems Separation of Foul and Surface Water Sewers Improved Maintenance Regimes Managing Overland Flows (Online Storage) Managing Overland Flows (Preferential Flowpaths) Land Management Practices Deculverting Watercourse(s) Other 'Pathway' Measures Improved Weather Warning Planning Policies to Influence Development Temporary or Demountable Flood Defences Social Change, Education and Awareness Improved Resilience and Resistance Measures Other 'Receptor' Measures

1 Do Nothing 3 2 -1 -2 0 -2 -3 3 In line with PAG the 'do nothing' option (no intervention and no maintenance) and 'do minimum' (continuation of current practise) 2 Do Minimum 3 20-10-10 3 should be taken forward to the detailed options assessment.

Minimal modification of current land structure could provide a 6 Flood Storage / Permeability g a N/A a g N/A 3 101125 3 significant flood storage area. The use of infiltration systems is potentially limited by the geology of the area.

Foul and surface water system already separate 7 Separate Surface Water and Foul Water Sewer Systems r 2

8 De-culvert / Increase Conveyance r N/A 2 0

Designating roads as flow paths would reduce flood risk from surrounding buildings. However this will need to be coupled with attenuation or increased drainage at the end of the flow path. Roads 9 Preferential / Designated Overland Flow Routes g N/A 3 210025 3 that channel water to some extent in present conditions are main access roads, so reducing access under flooding conditions may be undesirable.

10 Community Resilience a gga N/A 3 201014 2 The benefits will not outweigh the costs of such a measure

South Benfleet School and two pumping stations are in the PSWFH. 11 Infrastructure Resilience g a N/A 3 201014 2 The benefits of resilience measures will outweigh the costs. This is technically possible but the cost-benefit ratio is likely to be 12 Other - Improvement to Drainage Infrastructure G N/A 3 1-10011 2 negative. A combination of flood storage (Boyce Hill Golf Course and Benfelet Marsh) with land management will retain surface water runoff at 13 Other or Combination of Above gga 3 210025 3 desired points within the CDA. Community awareness will ensure people understand the risk. SOUTH ESSEX SURFACE WATER MANAGEMENT PLAN

CDA DESCRIPTION

Critical Drainage Area ID: CAS 2 New Thundersley

Surface water generally flows from the east to the west of the CDA. There are two distinct flow paths. Surface water accumulates in the flood storage area to the west Description: of the CDA and behind the embankment of the A130. This coincides with a Tributary of the Rawreth Brook which has been diverted under the road.

Flood Risk Surface Water, Ordinary Watercourse and Sewer Categorisation: 491 buildings of which 438 are residential properties >0.1m Property Count: 39 buildings of which and 25 are residential properties >0.3m 6 buildings of which 2 are residential properties >0.5m

Critical • Glenwood School, Montgomery School, Kingston School, The Robert Drake School Infrastructure: • Pumping Station

• There are historical flooding records along London Road, High Road, Ivy Road and Validation: Overton Road. • There is a record of sewer flooding along High Road.

Pluvial modelling indicates there are two main flow paths across the CDA. The first approximately follows the path a tributary of the Rawreth Brook, Everslet Road and Stansfield Road. The second flows between Chesterfield Avenue and London Road. PSWFH: The main residential areas affected by ponding are the Recreation Ground, Hornbeams and to the left of Rushbottom Lane. Surface water also accumulates in the storage area behind the east embankment of the A130.

Figure C 21 – Surface Water Flood Depth (1% AEP) Figures: Figure C 22 – Surface Water Flood Hazard (1% AEP) DRAIN LONDON SURFACE WATER OPTION SCORING MATRIX

Stage 1 - Identify Potential Measures

Critical Drainage Area ID: CAS 2 New Thundersley

Measure Opportunity Assessment Description Location / Specific Details Comments Could be implemented in new developments. Green Roof However these are costly and have limited surface a Generic Measure Throughout CDA water management potential. Further investigation is needed to assess the Soakaways a Generic Measure Throughout CDA infiltration potential due to geology. Further investigation is needed to assess the Swales a Generic Measure Throughout CDA infiltration potential due to geology. Further investigation is needed to assess the Permeable Paving a Generic Measure Throughout CDA infiltration potential due to geology. Throughout CDA - Schools, public Rainwater Harvesting G Generic Measure buildings and industrial buildings To be identified on site-by-site basis. SOURCE Create and enhance water Larger green spaces: recreational Detention Basins storage spaces in existing green and school grounds in the west of Modification of opens spaces to temporarily retain g and open spaces the CDA. stormwater Ponds and wetlands with Would require a permanent water supply, but could Ponds and Wetlands additional capacity to also provide additional social and environmental a accommodate runoff East of the CDA benefits. Bund to create accumulation and storage of flood Other 'Source' Measures g Development of Bund Coombe Wood water at the east of the woods. Increasing Capacity in Drainage Systems g PSWFH Separation of Foul and Surface Water Sewers r Foul and surface water system already separate Improved Maintenance Regimes G Generic Measure Throughout CDA To be identified on site-by-site basis. Watercourses are culverted in most places. The open section along the primary school fields could Managing Overland Flows (Online Storage) Increase channel capacity, such be developed to create a greater online storage A as a two stage channel. Robert Drake Primary School capacity. Alteration of road structure (increased pavement height and Enhance existing road structure to ensure surface Managing Overland Flows (Preferential Flowpaths) lower road depth) to define flow water flows remain in the road channel and do not g path of surface water Rushbottom Lane flow into houses.

PATHWAY Aeration of compact ground on In the east of the CDA (Coombe Increasing infiltration within the topsoils of the Land Management Practices sports fields. Increased Wood) and in the school and sports ground at the head of the catchment will g vegetation coverage. recreational grounds in the west. reduce the volume of surface water generated Deculverting Watercourse(s) r Watercourses are already open where possible Increase conveyance at this point where surface water is restricted. This will need to be in Other 'Pathway' Measures conjunction with Anglain Water and the Highways g Increase conveyance A130 Embankment Authority. Employ Extremer Weather Alert Improved Weather Warning service provided by Met Office Combine with SWMP mapped outputs to inform a and EA Throughout CDA emergency planners of areas to focus resources. Planning Policies to Influence Development G Generic Measure Throughout CDA For all new development. Temporary or Demountable Flood Defences g PSWFH Will be dependent on engagement opportunities with community. Social Change, Education and Awareness g Generic Measure Throughout CDA In areas with a large migration of population it will

RECEPTOR be difficult to undertake / pass on information from one property owner to other Temporary and permanent flood This could potentially be implemented across the Improved Resilience and Resistance Measures Throughout CDA a resilience CDA which is unlikely to be cost beneficial Other 'Receptor' Measures N/A SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 2 and 3 - Optons Identification and Short Listing

Critical Drainage Area ID: CAS 2 New Thundersley

Standard Measures Shortlisting Options SOURCE PATHWAY RECEPTOR

Option No. Option (Scheme Category) Comments Social Overall Technical Technical Economic Objectives Environmental Appropriate Measures Available? Take Forward Option to Detailed Assessment? Green Roof Green Soakaways Swales Paving Permeable Harvesting Rainwater Basins Detention Ponds and Wetlands Measures 'Source' Other Systems Drainage in Capacity Increasing Sewers Water and Surface Foul of Separation Regimes Maintenance Improved Storage) (Online Flows Overland Managing Flowpaths) (Preferential Flows Overland Managing Practices Land Management Watercourse(s) Deculverting Measures 'Pathway' Other Warning Weather Improved Development Influence to Policies Planning Defences Flood Demountable or Temporary and Awareness Education Change, Social Measures and Resistance Resilience Improved Measures 'Receptor' Other

1 Do Nothing 3 2-1-20-2-3 3 In line with PAG the 'do nothing' option (no intervention and no maintenance) and 'do minimum' (continuation of current practise) 2 Do Minimum 3 2 0-10-10 3 should be taken forward to the detailed options assessment.

This option is relatively easy to implement through the revision of the 3 Improved Maintenance Gg 3 211015 3 existing maintenance schedule. However this will only have localised benefits To implement this option into new developments would be relatively 4 Planning Policy G 3 220116 3 simple through planning policy.

Small scale rainwater harvesting, such as Water Butts can be installed in public buildings and schools. Planning policy should be sued to 5 Source Control, Attenuation and SUDS a aaaGg g 3 121127 3 ensure the implementation of these in new developments across the CDA. There are number of green spaces, of varying size and functionality that can be modified as multifunctional spaces to retain stormwater 6 Flood Storage / Permeability g a g A gg 3 101125 3 during flood events. Further investigation would be needed to assess the potential of detention basins or ponds, and to assess the infiltration potential in this area. 7 Separate Surface Water and Foul Water Sewer Systems r 2 0 Foul and surface water system already separate Increase the capacity of the culvert through the A130 embankment. 8 De-culvert / Increase Conveyance r g 3 010225 3 This will be undertaken in conjunction with Anglian Water. 9 Preferential / Designated Overland Flow Routes gg 3 0 2

10 Community Resilience a gga N/A 3 2-1-101 1 2 The benefits of such systems will not outweigh the costs.

11 Infrastructure Resilience g a N/A 3 2-10012 2 The benefits of such systems will not outweigh the costs.

Increase capacity and functionality of the existing above ground drain. 12 Other - Improvement to Drainage Infrastructure gg 3 210025 3 Increase the conveyance of surface water through the A130 embankment. A combination of flood storage systems through the CDA (Coombe Wood, Recreational Grounds) and increased conveyance through the 13 Other or Combination of Above gg3 120025 3 A130 embankment would reduce the risk of flooding to the properties in the PSWFH. SOUTH ESSEX SURFACE WATER MANAGEMENT PLAN

CDA DESCRIPTION

Critical Drainage Area ID: CAS 3 East Thundersley • Surface water generally flows from the west to the east of the CDA, towards the Prittle Brook. The contributing areas are Swans Green, the Wensley Road area and the Hart Road area. There is one PSWFH within the CDA. Significant ponding of surface water forms in West Wood, West Wood Gardens, Prittle Close, Rayleigh Description: Road and along The Chase. Much of this occurs within the vicinity of the Prittle Brook channel. • The eastern extent of the PSWFH coincides with the Prittle Brook fluvial flood zone 2 and 3, Flood Risk Surface Water and Ordinary Watercourse Categorisation: 233 buildings of which 209 are residential properties >0.1m Property Count: 37 buildings of which 36 are residential properties >0.3m 6 buildings of which 6 are residential properties >0.5m

Critical The Deanes School, Cedar Hall School, Thundersley Primary School and Westwood Infrastructure: Primary School.

There are records of historic flooding at Alderleys, The Chase, Southfield Close, Validation: Pendlestone and the junction of Shipwrights Drive and Kiln Road. There are no sewer flooding records in this CDA.

The pluvial modelling suggests the PSWFH follows the upstream channel of the Prittle Brook (where it is an ordinary watercourse). In addition, Queensmere and PSWFH: Rayleigh Road have been modelled to have significant volumes of ponded surface water runoff.

Figure C 23 – Surface Water Flood Depth (1% AEP) Figures: Figure C 24 – Surface Water Flood Hazard (1% AEP) SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 1 - Identify Potential Measures

Critical Drainage Area ID: CAS 3 East Thundersley

Increasing Capacity in Drainage Systems Increase conveyance of This will reduce the local flood risk, however may G stormwater from the site. PSWFH areas exacerbate the problem of flooding downstream. Separation of Foul and Surface Water Sewers r Already separate Improved Maintenance Regimes G Generic Measure Throughout CDA To be identified on site-by-site basis. This will help to attenuate the flow, and so reduce flow velocities along the flow path. This is especially to downstream areas of the catchment. Flow through the watercourse can be Managing Overland Flows (Online Storage) restricted/controlled, causing water to back up and Create attenuation areas in overflow, at times of high flow, into the open conjunction with main flow space before the urban area. This will create

PATHWAY g paths. West Wood additional amenity and biodiversity value.

Managing Overland Flows (Preferential Flowpaths) Adjust road structures to channel This will ensure flows stay within the road channel g and retain surface water flows Rayleigh Road and do not tend towards houses. Aeration of compact ground on Increasing infiltration within the topsoils of the Land Management Practices sports fields. Increased sports ground at the head of the catchment will g vegetation coverage. Throughout the CDA reduce the volume of surface water generated Deculverting Watercourse(s) r Watercourses are already open where possible Other 'Pathway' Measures N/A Employ Extremer Weather Alert Improved Weather Warning service provided by Met Office Combine with SWMP mapped outputs to inform a and EA Throughout CDA emergency planners of areas to focus resources. Planning Policies to Influence Development G Generic Measure Throughout CDA For all new development. Temporary or Demountable Flood Defences g PSWFH Will be dependent on engagement opportunities with community. Social Change, Education and Awareness g Generic Measure Throughout CDA In areas with a large migration of population it will be difficult to undertake / pass on information from RECEPTOR one property owner to other This could be applied to a large proportion of Improved Resilience and Resistance Measures buildings in the CDA and is unlikely to be cost a beneficial. Other 'Receptor' Measures N/A SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 2 and 3 - Options Identification and Short Listing

Critical Drainage Area ID: CAS 3 East Thundersley

Standard Measures Shortlisting Options SOURCE PATHWAY RECEPTOR

1 Do Nothing 3 2-1-20-2-3 3 In line with PAG the 'do nothing' option (no intervention and no maintenance) and 'do minimum' (continuation of current practise) 2 Do Minimum 3 2 0-10-10 3 should be taken forward to the detailed options assessment.

This option is relatively easy to implement through the revision of the 3 Improved Maintenance G N/A 3 211015 3 existing maintenance schedule. However this will only have localised benefits To implement this option into new developments would be relatively 4 Planning Policy G 3 220116 3 simple through planning policy. Source controls can be implemented in new developments. Small scale rainwater harvesting, such as Water Butts can be installed in all 5 Source Control, Attenuation and SUDS a aaaG N/A g 3 121127 3 properties. This will be largely influenced by planning policy and surface water runoff requirements. There are number of green spaces, of varying size and functionality that can be modified as multifunctional spaces to retain stormwater 6 Flood Storage / Permeability g a N/A ggN/A 3 101125 3 during flood events. Further investigation would be needed to assess the potential of detention basins or ponds, and to assess the infiltration potential in this area. 7 Separate Surface Water and Foul Water Sewer Systems r 2 0 systems are already separated

8 De-culvert / Increase Conveyance r N/A 2 0 little opportunity for this option

9 Preferential / Designated Overland Flow Routes g N/A 3 0 2 little opportunity for this option

10 Community Resilience a gga N/A 3 1-11012 2 The benefits of resilience measures is unlikely to outweigh the costs.

11 Infrastructure Resilience g a N/A 3 1-11001 2 There is no critical infrastructure within the PSWFH

Increase capacity and functionality of the existing above ground drain. 12 Other - Improvement to Drainage Infrastructure G N/A 3 210025 3 Replacement of the trash screen of the Prittle Brook along with improved maintaince A combination of these measures will reduce the volumes of surface 13 Other or Combination of Above gg g g 3 211228 3 water entering the drainage system, and ensures that the drainage system functions correctly. SOUTH ESSEX SURFACE WATER MANAGEMENT PLAN

CDA DESCRIPTION

Critical Drainage Area ID: CAS 4 Hadleigh

Surface water flows from the west to the east of the CDA. There is a tributary of the Description: Prittle Brook which is open along the open field to the south of Scrub Lane. A large section of this watercourse is culverted at the eastern extent of the CDA.

Flood Risk Surface Water and Sewer Categorisation: 53 buildings of which 46 are residential properties >0.1m Property Count: 1 buildings of which 1 are residential properties >0.3m 0 buildings >0.5m

Critical • Hadleigh Infant and Nursery School, Hadleigh Junior School Infrastructure: • Fire Station

• Flood records within the CDA are located at Greenacres, Church Road and The Validation: Crescent. • There is a sewer flooding record at the junction of London Road and Rectory Road.

• There is no PSWFH within this CDA. The greatest surface water flood depths have been modelled to be along Estate Road, the Avenue and St Davids Drive. PSWFH: • Due to maintenance issues, localised flooding occurs along the open channel of the Prittle Brook tributary south of the school playing fields

Figure C 25 – Surface Water Flood Depth (1% AEP) Figures: Figure C 26 – Surface Water Flood Hazard (1% AEP) SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 1 - Identify Potential Measures

Critical Drainage Area ID: CAS 4 Hadleigh

Small scale systems (Water Butts) installed in Rainwater Harvesting each property. New developments can incorporate

SOURCE large scale rainwater harvesting. In addition, this G Generic Measure Throughout CDA provides a non potable water supply.

Detention Basins Embankments or detention Hadleigh Infant school, and within Enhance existing capacity of open spaces to retain g basins to retain stormwater the masterplan of new development stormwater Enhance riparian habitats though online storage along watercourse These require a permanent water source, so will Ponds and Wetlands or offline storage in spaces need to be developed in conjunction with the a adjacent Hadleigh Infant school watercourse. Other 'Source' Measures N/A The Avenue, Brough Rd, The Increasing Capacity in Drainage Systems Increase conveyance through Crescent, Hazel Close, Woodfield This will reduce the local flood risk, however may g CDA Rd exacerbate the problem of flooding downstream. Separation of Foul and Surface Water Sewers r Already separate Improved Maintenance Regimes g Generic Measure Throughout CDA To be identified on site-by-site basis. Online storage area/ increased Limited space within the CDA to implement. Could Managing Overland Flows (Online Storage) channel capacity of channel be considered within the masterplan for g through park. Hadleigh Infant school redeveloping the area. Increase curb height of the southern side to the

PATHWAY Managing Overland Flows (Preferential Flowpaths) Adjustment of pavement height road to prevent surface water flows to buildings on a and road structure Estate Road this side. Reduce encroachment of Land Management Practices a impermeable surfaces Throughout CDA Majority of CDA being heavily urbanised Deculverting Watercourse(s) r Watercourse is already open where possible. Other 'Pathway' Measures N/A Employ Extremer Weather Alert Improved Weather Warning service provided by Met Office Combine with SWMP mapped outputs to inform A and EA Throughout CDA emergency planners of areas to focus resources. Planning Policies to Influence Development G Generic Measure Throughout CDA For all new development. To be implemented where surface water flooding Temporary or Demountable Flood Defences g Demountable flood barriers PSWFH area risk is greatest Will be dependent on engagement opportunities with community. Social Change, Education and Awareness g Generic Measure Throughout CDA In areas with a large migration of population it will

RECEPTOR be difficult to undertake / pass on information from one property owner to other Increase drainage along Improved Resilience and Resistance Measures preferential flow paths and areas reduce risk to those at greatest risk of surface g of ponding PSWFH areas water flooding Other 'Receptor' Measures N/A SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 2 and 3 - Options Identification and Short Listing

Critical Drainage Area ID: CAS 4 Hadleigh

Standard Measures Shortlisting Options SOURCE PATHWAY RECEPTOR easures

Option No. Option (Scheme Category) Comments Social Overall Technical Technical Economic Objectives Environmental Appropriate Measures Available? Measures Appropriate Take Forward Option to Detailed Assessment? Detailed to Option Forward Take Other 'Receptor' Measures 'Receptor' Other Green Roof Green Soakaways Swales Paving Permeable Harvesting Rainwater Basins Detention Ponds and Wetlands Measures 'Source' Other Systems Drainage in Capacity Increasing Sewers Water and Surface Foul of Separation Regimes Maintenance Improved Storage) (Online Flows Overland Managing Flowpaths) (Preferential Flows Overland Managing Practices Land Management Watercourse(s) Deculverting Measures 'Pathway' Other Warning Weather Improved Development Influence to Policies Planning Defences Flood Demountable or Temporary and Awareness Education Change, Social Improved Resilience and Resistance M

1 Do Nothing 3 2 -1 -2 0 -2 -3 3 In line with PAG the 'do nothing' option (no intervention and no maintenance) and 'do minimum' (continuation of current practise) should be taken forward to 2 Do Minimum 3 20-10-10 3 the detailed options assessment.

This option is relatively easy to implement through the revision of the existing 3 Improved Maintenance g N/A 3 211015 3 maintenance schedule. However this will only have localised benefits To implement this option into new developments would be relatively simple 4 Planning Policy G 3 220116 3 through planning policy. To implement this option into new developments would be relatively simply and through planning policy. Once an area has been identified as being in a 5 Source Control, Attenuation and SUDS a aaaG N/A a 3 011125 3 critical drainage area, policies to manage the surface water on the site are already in place. Further investigation would be needed to assess the potential of detention 6 Flood Storage / Permeability g a N/A g a N/A 3 101125 3 basins or ponds. Infiltration systems are suitable in the west of the CDA, as there is high infiltration potential in this area. 7 Separate Surface Water and Foul Water Sewer Systems r 2

8 De-culvert / Increase Conveyance r N/A 2 0 Limited opportunity for this due to large urban extent and limited open space

Designating roads as flow paths would reduce flood risk from surrounding 9 Preferential / Designated Overland Flow Routes a N/A 3 210025 3 buildings. However this will need to be coupled with attenuation or increased drainage at the end of the flow path. A combination of resistance measures, education and flood warning would be 10 Community Resilience A gggN/A 3 211015 3 beneficial in reducing flood damages Benefits of this will exceed the costs as there is no critical infrastructure in 11 Infrastructure Resilience ggN/A 3 2-11 0 1 3 2 areas of flooding This is technically possible but the cost-benefit ratio is likely to be negative. 12 Other - Improvement to Drainage Infrastructure g N/A 3 1-10 0 1 1 2

Combination of measures across the catchment will have a large effect across 13 Other or Combination of Above gg g 3 101125 3 the CDA. If they can be connected to form a 'green corridor' there will be additional ecological advantages. SOUTH ESSEX SURFACE WATER MANAGEMENT PLAN

CDA DESCRIPTION

Critical Drainage Area ID: CAS 6 Canvey Island

• There is a complex network of dykes, creeks and ditches (many of which are pumped) running through the CDA. • The majority of the CDA is within tidal and fluvial flood zone 2 and 3. Description: • The pluvial modelling indicates that there are no extensive areas of surface water flooding, due to the flat topography, limited overland flow and the managed system across the CDA.

315 buildings of which 285 are residential properties >0.1m Property Count: 2 buildings of which 2 are residential properties >0.3m 0 buildings >0.5m

• Schools: Frankwick Park, Castle View, Conelius Vermuyden, Canvey Junior, Critical William Read Primary, Winter Gardens Primary, Hawkesbury, Lubbins Park Community Primary, St Joseph’s Catholic Primary, Leigh Beck Junior. Infrastructure: • Pumping Stations • Ambulance Station, Police Station, Fire Station

• There are 12 historic flooding records within the CDA. Validation: • There are sewer flood records along Cedar Road and Heideburg Road.

• There is no PSWFH within the CDA. The pluvial modelling does not highlight any PSWFH: areas of significant flooding and the only flood risk from surface water is associated with drainage system failure.

Figure C 29 – Surface Water Flood Depth (1% AEP) Figures: Figure C 30 – Surface Water Flood Hazard (1% AEP) SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 1 - Identify Potential Measures

Critical Drainage Area ID: CAS 6 Canvey Island

Small scale systems (Water Butts) installed in each Rainwater Harvesting property. New developments can incorporate large scale rainwater harvesting. In addition, this provides SOURCE G Generic Measure Throughout CDA a non potable water supply. Furtherwick Park School playing Detention basins to retain fields, Linden Way Green Space, Detention Basins stormwater in existing green King George's Field Recreation Enhance existing capacity of open spaces to retain g space Ground, Small Gains Avenue stormwater Enhance riparian habitats though online storage along watercourse These require a permanent water source, so will Ponds and Wetlands or offline storage in spaces King Georges Field Recreation need to be developed in conjunction with the g adjacent Ground, Smallgains Avenue watercourse. Other 'Source' Measures N/A Increase conveyance through Investigation needed to determine the capacity of Increasing Capacity in Drainage Systems g CDA Across CDA the existing drainage system Separation of Foul and Surface Water Sewers r Already separate Improved Maintenance Regimes g Generic Measure Throughout CDA To be identified on site-by-site basis. Online storage area/ increased Managing Overland Flows (Online Storage) channel capacity of channel Investigation required to determine the a through park. Watercourses throughout CDA effectiveness of such a measure Limited opportunity to create preferential flow paths

PATHWAY Managing Overland Flows (Preferential Flowpaths) r as few significant flow paths modelled. Reduce encroachment of Land Management Practices a impermeable surfaces Throughout CDA Majority of CDA being heavily urbanised Deculverting Watercourse(s) r Watercourse is already open where possible. Other 'Pathway' Measures N/A Employ Extremer Weather Alert Improved Weather Warning service provided by Met Office Combine with SWMP mapped outputs to inform A and EA Throughout CDA emergency planners of areas to focus resources. Planning Policies to Influence Development G Generic Measure Throughout CDA For all new development. Few buildings modelled to be at risk of significant Temporary or Demountable Flood Defences Throughout CDA a Demountable flood barriers surface water flooding Will be dependent on engagement opportunities with community. Social Change, Education and Awareness g Generic Measure Throughout CDA In areas with a large migration of population it will

RECEPTOR be difficult to undertake / pass on information from one property owner to other Increase drainage along Improved Resilience and Resistance Measures preferential flow paths and areas Throughout CDA Few buildings modelled to be at risk of significant a of ponding surface water flooding Other 'Receptor' Measures N/A SOUTH ESSEX SURFACE WATER OPTION SCORING MATRIX

Stage 2 and 3 - Options Identification and Short Listing

Critical Drainage Area ID: CAS 6 Canvey Island

Standard Measures Shortlisting Options SOURCE PATHWAY RECEPTOR easures

This option is relatively easy to implement through the revision of the existing 3 Improved Maintenance g N/A 3 211015 3 maintenance schedule. However this will only have localised benefits To implement this option into new developments would be relatively simple 4 Planning Policy G 3 220116 3 through planning policy. To implement this option into new developments would be relatively simply and through planning policy. Once an area has been identified as being in a 5 Source Control, Attenuation and SUDS a aaaG N/A a 3 011125 3 critical drainage area, policies to manage the surface water on the site are already in place. Further investigation would be needed to assess the potential of detention 6 Flood Storage / Permeability ggN/A aaN/A 3 1-11 1 2 4 2 basins or ponds. Benefits are unlikely to exceed costs 7 Separate Surface Water and Foul Water Sewer Systems r 2

8 De-culvert / Increase Conveyance r N/A 2 0

9 Preferential / Designated Overland Flow Routes r N/A 2 0

10 Community Resilience Aag a N/A 3 221016 3 Community awareness will be most benefitital

This is technically possible but the cost-benefit ratio is likely to be negative. 11 Infrastructure Resilience aaN/A 3 2-11 0 1 3 2

This is technically possible but the cost-benefit ratio is likely to be negative. 12 Other - Improvement to Drainage Infrastructure g N/A 3 1-10 0 1 1 2

13 Other or Combination of Above 2