Appendix D – Summary of Intermediate Risk Assessment (Hotspots Storyboard)
Maidstone & Malling Surface Water Management Plan – Hotspots Storyboard
Notes:
1. Each Hotspot reviewed has been taken from a combination of individual stakeholder meetings, historic and EA FMfSW datasets. 2. Each Hotspot area has been amended marginally to conform to the higher level of detail required for this analysis. 3. All historic flooding incidents comprise of a combination of SWMP anecdotal data which has not been fully filtered so should only be used as a guide. 4. A brief economic assessment has been undertaken for each hotspot area by determining how many address points fall within a 5m buffered zone of the shallow 1 in 30yr EA FMfSW.
LEGEND for Flooding Data Figures: Abbreviations: EA Main River KCC – Kent County Council MBC – Maidstone Borough Council Hotspots TMBC – Tonbridge & Malling Borough Council EA 1 in 30yr FMfSW (0.1m - 0.3m) SW – Southern Water EA – Environment Agency EA 1 in 30yr FMfSW (>0.3m) HA – Highways Agency Historic Flooding
Stakeholder Information General Flow Direction
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Hotspot ID Area Stake-holder
M20, 01 Maidstone Borough Council Junction 6
Hotspot Information Flooding Data Conclusion
Hotspot Area Actual Flooding: Flooding incidents Initial 2 0.28 (km ) along the M20 and in Boarley Lane. Assessment: No Significant Risk Modelled Flooding: Flooding of Actual Flooding properties in Boarley Lane. Source: No. of Flooding Stakeholder Info: The one historic Watercourse 8 Incidents flooding incident is believed to be caused by a significant fluvial event and Pathway: is not associated to surface water flood Highway Occurrence 2002,2009, risk. The motorway culvert may be 2010,2011 acting as a restriction on the Receptors: watercourse and exacerbating fluvial Trunk Road flood risk. Source of Data MBC & HA Mapped Features: Urban and Key Recommendation: Trunk Road. No further work Predicted Flooding required Main type of Receptors: Pumping No. of buildings Station and Trunk road. within the EA’s 1 19 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
M20, 02 Tonbridge & Malling Borough Council Near Larkfield
Hotspot Information Flooding Data Conclusion
Hotspot Area Actual Flooding: Flooding incidents Initial 2 0.35 (km ) along the M20, near Larkfield and in Assessment: Ditton Place. No Significant Risk
Actual Flooding Modelled Flooding: Flooding of properties in Station Road, Ditton Place Source: No. of Flooding and Bell Lane. Watercourse 3 Incidents Stakeholder Info: TMBC stated Pathway: properties on Cobdowne Close had Overland Flow Occurrence 2006, 2010, experienced local flooding but this was Periodic caused by fluvial flooding and the issue Receptors: has since been resolved. There is no Residential known flooding of the playing fields Properties Source of Data TMBC & HA adjacent to the sports centre.
Mapped Features: Urban and Key Trunk Recommendation: Predicted Flooding Road. No further work required No. of buildings Main type of Receptors: Pumping within the EA’s Station, Trunk road and Residential.
1 in 30yr 94 shallow flood extent
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Hotspot ID Area Stake-holder
03 Aylesford Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Hotspot Area Actual Flooding: Flooding of Initial Assessment: 2 0.10 (km ) Cobtree Manor due to low lying Risk Identified land.
Actual Flooding Modelled Flooding: None. Source: Drainage Ditches No. of Flooding Stakeholder Info: MBC stated 4 Incidents there has been curtilage flooding Pathway: Overtopping and the area is low-lying and ditches ditch are poorly maintained, ditch Occurrence 2004,2005, improvements work has been Receptors: Residential 2008 undertaken which has resolved the Properties flood risk.
Source of Data MBC Mapped Features: Rural Recommendation: Improve awareness of Main type of Receptors: ditch maintenance and Predicted Flooding Residential. clearance
No. of buildings Existing Schemes: within the EA’s 1 Ditch clearance 0 in 30yr shallow flood extent Possible Options: Continued ditch maintenance.
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Hotspot ID Area Stake-holder
04 Maidstone Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Hotspot Area Actual Flooding: Curtilage flooding Initial Assessment: 2 0.06 (km ) of Turkey Mill. Risk Identified
Modelled Flooding: Overtopping of Actual Flooding the River Len. Source: Watercourse & Spring No. of Flooding Stakeholder Info: MBC stated 1 Incidents there has been curtilage flooding at Pathway: Overtopping & the Mill, there is a possible natural overland flow spring in area which emerges Occurrence approximately 60-70yards from the Receptors: Residential mill. Properties
Source of Data MBC Mapped Features: Semi-urban. Recommendation: Main type of Receptors: Further investigation Predicted Flooding Commercial. required to assess water table and spring location No. of buildings within the EA’s Possible Options: 1 in 30yr 20 Management of overland shallow flood flows to prevent flooding extent from spring
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Hotspot ID Area Stake-holder
05 Maidstone Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Hotspot Actual Flooding: Flooding incident Initial Assessment: 2 0.03 Area (km ) along the A229. Risk Identified
Modelled Flooding: Flooding across Actual Flooding both carriageways of A229. Source: Surface run-off
No. of Stakeholder Info: Highway drains Pathway: Highway Flooding 1 become overloaded during heavy Incidents rainfall. Highway known to become Receptors: Highway impassable with most severe flooding occurring at the junction of Sheals Occurrence Crescent and Loose Road. Believed to Recommendation: only be highway flooding, but MBC state Further investigation this is on a key main road into required to assess Source of Maidstone. overland flow management MBC Data and surface water storage.
Mapped Features: Urban and Key Possible Options: Predicted Flooding Road. Upstream attenuation of surface water runoff in No. of Main type of Receptors: Key Road. open playing fields and buildings prioritised gully within the maintenance. 37 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
06 West Malling Tonbridge & Malling Borough Council
Hotspot Information Flooding Data Conclusion
Hotspot Actual Flooding: Highway flooding in Initial Assessment: 2 0.25 Area (km ) Pikey Lane. Risk Identified
Modelled Flooding: Flooding of Actual Flooding highway in Pikey Lane and of Farms in Source: Surface run-off Broadwater Road. No. of Pathway: Highway Flooding 1 Stakeholder Info: TMBC stated Incidents highway flooding occurs possibly caused Receptors: Highway by runoff from surrounding land into poorly maintained highway drainage Occurrence ditches. Recommendation: Awareness raising for Mapped Features: Rural. landowners to maintain Source of MBC ditches accepting runoff Data Main type of Receptors: Agriculture from surrounding land. and Residential. Possible Options: Predicted Flooding Awareness raising for landowners to maintain No. of ditches accepting runoff buildings from surrounding land. within the 17 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
07 Tovil Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Initial Assessment: Overtopping of the River No Significant Risk Hotspot Area Loose. 2 0.22 (km ) Modelled Flooding: Source: Watercourse Flooding of properties in Actual Flooding Allnut Mill Close, Tovil Hill Pathway: Overtopping and Woodbridge Drive. No. of Flooding Receptors: Residential 6 Incidents Stakeholder Info: Local Properties watercourse overtopping due to debris in channel, a Occurrence 2001, 2005, 2006 one off issue. Flood risk is Recommendation: thought to be mainly No further work required caused by fluvial flooding. Source of Data MBC Mapped Features: Urban.
Predicted Flooding Main type of Receptors: Residential and Industrial
No. of buildings Estate. within the EA’s 1 186 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
08 Snodland Tonbridge & Malling Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Overloaded Initial Assessment: Hotspot Area sewers in Saltings Road. No Significant Risk 2 0.06 (km ) Modelled Flooding: Flooding of properties in Saltings Road and Source: Sewerage system Actual Flooding Ashbee Close. Pathway: Highway No. of Flooding Stakeholder Info: No known 1 Incidents surface water relating flood risk Receptors: Residential in the area. properties
Occurrence 2003 Mapped Features: Urban. Recommendation: Main type of Receptors: No further work required Source of Data SW Residential.
Predicted Flooding
No. of buildings within the EA’s 1 in 49 30yr shallow flood extent
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Hotspot ID Area Stake-holder
09 M20, Junction 7 Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Flooding Initial Assessment: Hotspot 2 1.34 incidents along the M20 and in No Significant Risk Area (km ) Grange Lane.
Modelled Flooding: Flooding Actual Flooding Source: Surface run-off along M20.
Highway No. of Pathway: Stakeholder Info: No known Flooding 9 specific surface water related Highway Incidents Receptors: flooding issues.
Mapped Features: Urban and Key Occurrence 2002,2007, Recommendation: Trunk Road. No further work required 2009,2010 Main type of Receptors: Pumping Source of MBC, HA Station, Sewage Treatment Works Data and Residential.
Predicted Flooding
No. of buildings within the 37 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
10 Bearsted Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Blockage of Initial Assessment: Hotspot 2 0.16 stream in Mallings Drive and Risk Identified Area (km ) flooding in The Street.
Modelled Flooding: Flooding of Actual Flooding properties in Mallings Drive, Cross Source: Watercourse
Keys and The Street. No. of Pathway: Overtopping Flooding 2 Stakeholder Info: No known Incidents specific problems but there has Receptors: Residential
been some changes in watercourse properties & highway levels by landowners constructing Occurrence 2000, 2006 features within the watercourse.
Recommendation: Mapped Features: Urban and Raise awareness to possible Source of MBC railway line. changes in watercourse levels Data which may impact on fluvial Main type of Receptors: flood risk. Residential. Predicted Flooding Possible Options: Raise awareness to residents No. of and possible removal of buildings structures within watercourse. within the 76 Attenuate flows upstream by EA’s 1 in throttling the railway culverts. 30yr shallow flood extent
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Hotspot ID Area Stake-holder
11 Bearsted Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Overtopping of Initial Assessment: Hotspot 2 0.08 the River Len due to a blockage. No Significant Risk Area (km )
Modelled Flooding: Flooding of
properties in Discovery Road and Actual Flooding Lenside Drive. Source: Watercourse
No. of Stakeholder Info: No known Pathway: Overtopping Flooding 2 surface water flood risk related Incidents issues. Receptors: Residential
properties & highway
Mapped Features: Urban Occurrence 1999, 2005
Main type of Receptors: Pumping Recommendation: Station and Residential. No further work required Source of MBC Data
Predicted Flooding
No. of buildings within the 23 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
12 Maidstone Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Overloaded Initial Assessment: Hotspot 2 0.13 sewers in Tovil Road, Coombe No Significant Risk Area (km ) Road and Brenchley Road.
Modelled Flooding: Flooding of Actual Flooding properties in Old Tovil Road and Source: Sewerage system
College Road. No. of Pathway: Highway Flooding 3 Stakeholder Info: No known Incidents surface water related flooding Receptors: Residential
issues. properties & highway
2000, 2009, Occurrence 2010 Mapped Features: Urban
Recommendation: Main type of Receptors: No further work required Source of SW Residential. Data
Predicted Flooding
No. of buildings within the 48 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
13 East Malling Tonbridge & Malling Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Overtopping of Initial Assessment: Hotspot 2 0.19 Clare Park Lake into Blacklands. Risk Identified Area (km )
Modelled Flooding: Flooding of
properties in Blacklands, Elm Actual Flooding Crescent and Beech Road. Source: Watercourse &
Sewerage system No. of Stakeholder Info: TMBC stated Flooding 1 during high flows in the Pathway: Overtopping Incidents watercourse the bypass channel is
used which has overtopped in the Receptors: Residential past flooding the highway and properties & highway Occurrence Periodic basement properties on Blacklands.
SW stated there is infiltration into
the foul sewer resulting in Recommendation: Source of TMBC Blacklands pumping station Further investigation required Data becoming overloaded.
Possible Options: Mapped Features: Semi-urban Upstream attenuation in rural Predicted Flooding and School. areas and lining the foul sewers to prevent infiltration, however, No. of Main type of Receptors: laterals may still leak. buildings Residential and School. within the 163 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
14 West Malling Tonbridge & Malling Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Flooding in Ryarsh Initial Assessment: Hotspot 2 0.09 Lane Risk Identified Area (km )
Modelled Flooding: Flooding of Source: Watercourse
properties in Ryarsh Lane and Frog Actual Flooding Lane. Pathway: Highway
No. of Stakeholder Info: TMBC stated there is Receptors: Residential Flooding 1 some flood risk on Frog Lane which may properties, railway line & Incidents be caused by the restricted culvert highway
running under the railway line. TMBC
also confirmed surface water flood risk Occurrence is present on Swan Street adjacent to St Recommendation:
Marys Abbey and at the junction with Investigate feasibility to Lavenders Road caused by runoff which accelerate sewer rehab Source of SW occurs periodically. SW confirmed there work. Data is heavy root ingress into the 300mm dia
combined sewer which runs under the Existing Schemes: railway line embankment, this has Sewer rehab work is to be Predicted Flooding resulted in curtilage flooding with the risk undertaken to remove of internal flooding present. roots from the sewer in the No. of next 2 years. buildings Mapped Features: Rural and Railway within the 58 Line. Possible Options: EA’s 1 in Relining the existing sewer 30yr shallow Main type of Receptors: Residential. to prevent future root flood extent ingress.
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Hotspot ID Area Stake-holder
15 Maidstone Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Flooding in Upper Initial Assessment: Hotspot 2 0.04 Fant Road. No Significant Risk Area (km )
Modelled Flooding: Flooding of
properties in Upper Fant Road. Source: Surface runoff Actual Flooding
Stakeholder Info: No known surface Pathway: Overland flow No. of water related flooding issues. Flooding 2 Receptors: Residential Incidents Mapped Features: Urban. properties & highway
Main type of Receptors: Residential. Occurrence 2001 Recommendation:
No further work required
Source of MBC Data
Predicted Flooding
No. of buildings within the 124 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
16 Teston Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Highway flooding in Initial Assessment: Hotspot 2 0.04 Teston Lane. No Significant Risk Area (km )
Modelled Flooding: Flooding of car
park and land adjacent to the railway Source: Surface runoff Actual Flooding line.
Pathway: Overland flow No. of Stakeholder Info: No known surface Flooding 3 water related flooding issues. Receptors: Highway & car Incidents park
Mapped Features: Rural and Railway
2001, 2004, Line. Occurrence 2005 Recommendation:
Main type of Receptors: Public Car No further work required Park. Source of MBC Data
Predicted Flooding
No. of buildings within the 1 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
17 Loose Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Flooding of highway Initial Assessment: Hotspot 2 0.05 Mill Street. Risk Identified Area (km )
Modelled Flooding: Flooding of
properties along Mill Street and Vale Source: Watercourse Actual Flooding Road.
Pathway: Overtopping No. of Stakeholder Info: Known heavy silting Flooding 2 occurring on the Loose Stream which Receptors: Residential Incidents was de-silted in 2007. properties & highway
Mapped Features: Rural. Occurrence 2001, 2005 Recommendation:
Main type of Receptors: Residential. Confirm if proposed Parish scheme will resolve all Source of MBC flood risk in the area. Data
Existing Schemes: Parish Council scheme Predicted Flooding grant for de-silting local watercourse and possible No. of attenuation pond. buildings within the 58 Possible Options: EA’s 1 in Prioritised maintenance of 30yr shallow existing watercourse. flood extent
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Hotspot ID Area Stake-holder
18 Otham Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: One flooding event Initial Assessment: Hotspot 2 0.05 caused curtilage flooding along White No Significant Risk Area (km ) Horse Lane.
Modelled Flooding: Flooding of Source: Surface runoff Actual Flooding properties in White Horse Lane and
Honey Lane. Pathway: Overland flow No. of
Flooding 3 Receptors: Residential Incidents Stakeholder Info: No known surface properties & highway
water related flooding issues.
2000, 2001, Occurrence 2002 Mapped Features: Rural Recommendation:
No further work required Main type of Receptors: Residential. Source of MBC Data
Predicted Flooding
No. of buildings within the 14 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
19 Birling Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Blocked culvert Initial Assessment: Hotspot 2 1.03 resulting cartilage flooding of the No Significant Risk Area (km ) RSPCA centre.
Modelled Flooding: Flooding to Source: Surface runoff Actual Flooding commercial building.
Pathway: Overland flow No. of Stakeholder Info: No known surface Flooding 1 water related flooding issues. Receptors: Residential Incidents properties & highway
Mapped Features: Rural
Occurrence 2000 Main type of Receptors: Commercial Recommendation:
building. Installation of trash screen to prevent future culvert Source of IDB blockages. Data
Possible Options: Installation of trash screen Predicted Flooding to prevent future culvert blockages. No. of buildings within the 0 EA’s 1 in 30yr shallow flood extent
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Hotspot ID Area Stake-holder
20 Mill Street Maidstone Borough Council
Hotspot Information Flooding Data Conclusion
Actual Flooding: Known flood risk from Initial Assessment: Hotspot 2 0.34 excessive vegetation growth within the No Significant Risk Area (km ) channel reducing conveyance of flows.
Modelled Flooding: Predicted flooding Source: Watercourse Actual Flooding indicated at location of watercourse
becoming culverted flooding residential Pathway: Overtopping No. of premises. Flooding 1 Receptors: Residential Incidents Stakeholder Info: Known flood risk properties
from excessive vegetation growth within
the channel reducing conveyance of Occurrence 2000 flows. Recommendation:
No further work required. Mapped Features: Residential and Source of IDB Railway line Existing Schemes: Data Maintenance carried out Main type of Receptors: Residential. by housing association.
Predicted Flooding
No. of buildings within the 0 EA’s 1 in 30yr shallow flood extent
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