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Raingarden - Newmarket - All Saints School
Credits: Anglian Water/Atkins
Incorporating SuDS Solutions into Long-term Strategic Growth Planning
Titiksh Patel and Ben Mauck17 October 2018
Outline
› Background of the PR19 Growth Strategies
› Methodology – Process Development
› Technical Details
› Hydraulic Modelling
› Conclusions
Background
› The Anglian Water region is one of the fastest growing in the UK
› As part of PR19 planning for AMP7 Anglian Water needed to develop long term catchment strategies to manage growth risk
› The objective of the project is to understand increasing risk on the sewerage network and develop catchment strategies to meet two future design horizons:
• 2027;
• Long-term >2027 (up to and including 2040-45)
Long-termStrategic
Sustainable
Planning with
Confidence
Background – Catchment Prioritisation
› Confidence Assessment of the Growth Forecast was done based on local Plan status; Unknown, Emerging or Under Consultation
› Anglian Water Carried out Initial Catchment Screening and Seven out of the Finally Filtered Gold Catchments were Allocated to Atkins to carry out the Detailed Appraisal
Bronze >>>> Silver >>>> Gold
Source: Water Recycling Long-Term Plan (WRLTP), Anglian Water
Methodology
Project Phases
High Level Optioneering
• 25 % Area Removal & Offline Storages
Strategic Optioneering
• Targeted Area Removal from SuDS Opportunity
Mapping Tool & Flow Conveyance
Delivery Strategy • Year-on-Year Scenario Analysis• First Point of Detriment – Flow Monitoring• GIS Mapping Query to identify Flooding & Growth
Overlaps
Phase 1
Phase 2
Phase 3
Methodology - SuDS Opportunity Mapping
Opportunity mapping generated for each
catchment across the Anglian Water region
Engineering
and
geospatial
constraints
Type of
SuDS
Technical Details – Growth Modelling & Scenarios
› Growth - GIS Tool
› Development details (Nr. of Dwellings & PCC)
› Represented Development Storage
› Compliant with Anglian Water Specifications
› Modelling Scenarios
› Scenario 1 – until 2027 (No CC)
› Scenario 2 – Long-term >2027 (No CC)
› Climate Change Scenarios
› Scenario 1 – until 2027 (10 % uplift)
› Scenario 2 – Long-term>2027 (20 % uplift)
Hydraulic Modelling – Detriment Analysis
› Flooding: Develop SuDS Hybrid Solutions for Detriment of >10 % or 25 m3 and new flooding
for a 1 in 30 year return period
› Overflows: Develop SuDS Hybrid Solutions for Detriment of >1 m3 for a 1 in 5 year return
period.
Hydraulic Modelling – Solution Hierarchy
SuDS
› Blanket removal of 25 % of impervious surfaces (Phase 1 – High level)
› SuDS Opportunity mapping (Phase 2)
Sewer upsize
› Utilise downstream network capacity
Offline Storage
› Provide additional localised storage at feasible locations
Catchment A
Type of SuDSConventional
Options
Tree Pit 10 units
• 2257 m of
Sewers upsized
• 1432 m3
of off-
line storage
• 613 m3
of on-line
storage
• 2 Sealed
Manholes
Bioretention 47 m2
Swales 1127 m3
Attenuating Rain
Gardens66 m2
Disconnect Downpipes 47 m3
Filter Drains 69 m3
Permeable Block
Paving23 m2
Attenuation Pond 16 m3
Rain Gardens (Surface) 1692 m2
Soakaway 28 m3
Worst Case: Scenario 2 (>2027 + 20 % CC):
SuDS + Conventional SolutionsSuDS Hybrid Solution Summary
Catchment B
Worst Case: Scenario 2 (>2027 + 20 % CC):
SuDS + Conventional Solutions
Type of SuDSConventional
Options
Tree Pit 1 units
• 10 527 m of
Sewers upsized
• 6 071 m3 of off-line
storage
• 1 328 m3 of on-line
storage
• 14 Sealed
Manholes
Wetlands 1 m3
Bioretention 40 m2
Swales 355 m3
Attenuating Rain
Gardens20 m2
Disconnect Downpipes 11 m3
Filter Drains 23 m3
Permeable Block
Paving23 m2
Attenuation Pond 1 m3
Green Roof 41 m2
Rain Gardens
(Surface)1352 m2
Soakaway 21 m3
SuDS Hybrid Solution Summary
Delivery Strategy and Growth Profiling
› Trigger Points
› Baseline SuDS Removal
› Peak flow and volume analysis
› Overlap Analysis
› Flooding locations Vs Growth detriments
0 0765
15152353
36144477
51995754
66097604
84879325
1017010822
Y2013_14 Y2014_15 Y2015_16 Y2016_17 Y2017_18 Y2018_19 Y2019_20 Y2020_21 Y2021_22 Y2022_23 Y2023_24 Y2024_25 Y2025_26 Y2026_27 Y2027_28
Bu
ild
Ou
t R
ate
Year
Ensure solution of greatest cost benefit is promoted for Long-term investment.
Challenges and Limitations
› Growth Sites Data:
› Limited Growth Details – Polygons, Size and Connection Points
› Modelling Challenge:
› Model Quality/Confidence – Need for future surveys and verification
› Model Complexity – Stability Issues & non-linear response
› Solution Feasibility:
› SuDS – Greater Stakeholder Engagement required
› Constructability of the Capital Schemes at an early stage is not possible
Conclusions
› Value of Strategic Assessments
› More confidence in the early stages of the planning process for Anglian Water
› Collaborative approach with the Anglian Water stakeholders
› Sustainable and hybrid solutions can be incorporated as part of the growth scheme
› Developed robust modelling process for future large scale strategic growth studies
Cheaper >>> Faster >>> Smarter >>> Better
Thank You!
Acknowledgements:
› Kerry Rhodes, Supply Demand Planning Manager (Anglian Water)
› Vanessa Greaves, Lead Infrastructure Modeller (Anglian Water)
› Neil Breton, Principal Hydraulic Engineer (Atkins, Member of the SNC Lavalin Group)