1. 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
SMALL PROJECT OF THE YEAR
British Construction Industry Awards 2018

2. 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

3. 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)

4. 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

5. 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

6. 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

7. 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

8. 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)

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

10. 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)

11. 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)

12. 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

13. 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

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