Developing a Sensitive and Sustainable Approach to Managing Flood Risk: Kingsmoor, Harlow Pluvial Flood Alleviation Scheme TOM PALMER FdSc BSc (Hons) Project Design Engineer Essex County Council tom.palmer@essex.gov.uk 03330 139511 SMALL PROJECT OF THE YEAR British Construction Industry Awards 2018

Essex Capital Programme Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Essex Capital Programme 5 year, £19m programme Individual schemes funded from programme and topped up with grants from the EA Projects selected by prioritising Critical Drainage Areas identified within SWMP’s and s19 report locations Feasibility and Option Optimisation studies undertaken with gate reviews prior to design and delivery stage Kingsmoor is an area within the south west of Harlow Harlow developed heavily following the war, lots of watercourses lost or piped Kingsmoor CDA slopes from south to north with Pardon and Risden Woods at the top along with Crematorium and Kingsmoor public open space Recorded flooding from surface water to 20 properties, from surface water sewers surcharging from another 20 148 residential and 6 commercial form 5% AEP 5 year capital programme scheme locations within Essex

Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Location and Problem Kingsmoor is an area in the south west of Harlow, Essex Heavily developed between 1950 and 1980 Rural upstream, developed downstream Recorded internal property flooding to 20 properties from surface water and 20 from sewers, most from a single storm event in 2006 Residential estate access road frequently made impassable due to flooding Issues with silt and debris from farmland upstream entering piped systems Modelled risk to 179 properties and 9 businesses from a 1% AEP event Kingsmoor is an area within the south west of Harlow Harlow developed heavily following the war, lots of watercourses lost or piped Kingsmoor CDA slopes from south to north with Pardon and Risden Woods at the top along with Crematorium and Kingsmoor public open space Recorded flooding from surface water to 20 properties, from surface water sewers surcharging from another 20 148 residential and 6 commercial form 5% AEP Kingsmoor Critical Drainage Area (CDA)

Kingsmoor Area Flooding Photos Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Kingsmoor Area Flooding Photos Kingsmoor is an area within the south west of Harlow Harlow developed heavily following the war, lots of watercourses lost or piped Kingsmoor CDA slopes from south to north with Pardon and Risden Woods at the top along with Crematorium and Kingsmoor public open space Recorded flooding from surface water to 20 properties, from surface water sewers surcharging from another 20 148 residential and 6 commercial form 5% AEP Photographs courtesy of Harlow DC

Scheme Development Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Feasibility and Option Optimisation studies undertaken by Jacobs Determined that a large earth bund and storage area provided the greatest benefits Reviewed in conjunction with Harlow District Council and leaky dams and pond de-silting aspects were proposed to better mitigate against silt The number and positioning of dams changed after discussions with Harlow DC based on known flood flow routes Potential dam locations identified and finalised following site meetings Kingsmoor is an area within the south west of Harlow Harlow developed heavily following the war, lots of watercourses lost or piped Kingsmoor CDA slopes from south to north with Pardon and Risden Woods at the top along with Crematorium and Kingsmoor public open space Recorded flooding from surface water to 20 properties, from surface water sewers surcharging from another 20 148 residential and 6 commercial form 5% AEP Location of proposed measures

Constraints and Considerations Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Constraints and Considerations Site Constraints: Local Nature Reserve (LNR) Ancient Woodlands SSSI’s (pedunculate woodland) Crematorium Footpaths and public access Proximity to residential areas Local ecology (hedges, trees, wildlife) Considerations: Use and type of machinery Working methods Noise and working hours Vehicle movements and re-use of spoil Sustainability (design and construction) Key site constraints

Mitigation Measures Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Early engagement with stakeholders and partners Dam positions adjusted to reduce impact to woodland and utilise existing morphology and features Use of volunteer group to help clear woodland areas Use of wood sourced from within woodlands as part of existing management plan Use of heavy horses to move materials into position and dams installed by hand Footpath diverted with unadopted path on bund crest Work stopped for funeral processions Grassland Management Plan created for Local Nature Reserve area Discussions with ecologists and arboriculturalists and Natural England to ensure proposals feasible and deliverable (NE Consents required) Photo courtesy of Place Services

Opportunities Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Woodland clearances chance to improve wider area (in line with SSSI status) Ecology and biodiversity in woodland and ponds Local amenity, promotion of woodland Signage explaining scheme, awareness raising Education: woodlands frequently visited by schools Footpath inconsistencies, chance to correct Earth bund seeded with grasses and wildflowers Innovative Grassland Management Plan for whole LNR rather than compensatory like for like area replacement GMP implemented to improve floral diversity of area Knock-on positive impact on local bird bat and animal populations Results in better linkage of two SSSI woodland areas Site boundary (red) and Local Nature Reserve (blue)

Scheme Photos: Leaky Dams During Construction Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Scheme Photos: Leaky Dams During Construction Photos courtesy of Harlow DC

Scheme Photos: Leaky Dams and Ponds Post Construction Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Scheme Photos: Leaky Dams and Ponds Post Construction Leaky dams and pond de-silting works immediately after completion (November 2017)

Scheme Photos: Leaky Dams and Ponds Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Scheme Photos: Leaky Dams and Ponds Leaky dams and ponds 5 months after works undertaken (April 2018)

Scheme Photos: Earth Bund During and Post Construction Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Scheme Photos: Earth Bund During and Post Construction Top and bottom far left photos courtesy of TopBond PLC. Bottom right photo courtesy of Place Services

Scheme Summary and Key Outcomes Harlow, Kingsmoor Pluvial Flood Alleviation Scheme Scheme Summary and Key Outcomes Leaky dams completed November 2017, bund completed July 2018 Total scheme costs £440k, pond de-silting and leaky dam aspects £42.8k Flood protection to 43 properties from a 5% AEP event, depth reductions to many others Carbon assessment: 94.4t of CO2 saved Flood mitigation measures can be delivered in sensitive areas! Flood alleviation works as an opportunity for wider benefits to ecology, biodiversity, water quality and amenity, and for raising flood awareness Learning for other schemes Partnership working essential to project success Toads and mint returning to a pond

Thank You Harlow, Kingsmoor Pluvial Flood Alleviation Scheme TOM PALMER FdSc BSc (Hons) Project Design Engineer Essex County Council Flood and Water Management Team tom.palmer@essex.gov.uk 03330 139511 Kingsmoor Flood Alleviation Scheme SMALL PROJECT OF THE YEAR British Construction Industry Awards 2018