Jason Harper Thames Water Property Searches Understanding SuDS The importance of Sustainable urban Drainage Systems Jason Harper Thames Water Property Searches

Session overview. The guidance and regulation regarding SuDS and new developments. What SuDS are and how they work. The need for SuDS and their benefits. How to assess a site’s suitability for SuDS. Explain the guidance and rules in place for SuDS for new developments. Describe how SuDS work and why they’re relevant to property management and new developments. Review the design principles of SuDS, assess the drainage hierarchy and know about variation in SuDS suitability for different sites.

Sustainable Urban Drainage Systems SuDs Sustainable Urban Drainage Systems “SuDS are designed to control surface water run-off close to where it falls and to mimic natural drainage as closely as possible.”

Flood Types Different types of flood can also have different effects in terms of their impact, damage and cost, both financially and to the people who experience them Fluvial (River) Flooding - Occurs when rivers burst their banks as a result of sustained or intense rainfall. Coastal Flooding - Caused by extreme tidal conditions including high tides, storm surges and tsunamis. Pluvial (Surface Water) Flooding - Occurs when an extremely heavy downpour of rain saturates drainage systems and the excess water cannot be absorbed. Reservoir Flooding - ccur as a result of dam failure. This type of flooding is rare. The impact of flood in the event of dam failure eg Edgbaston Reservoir in Birmingham, UK is extensive.

Flood Types Different types of flood can also have different effects in terms of their impact, damage and cost, both financially and to the people who experience them Fluvial (River) Flooding - Occurs when rivers burst their banks as a result of sustained or intense rainfall. Coastal Flooding - Caused by extreme tidal conditions including high tides, storm surges and tsunamis. Pluvial (Surface Water) Flooding - Occurs when an extremely heavy downpour of rain saturates drainage systems and the excess water cannot be absorbed. Reservoir Flooding - ccur as a result of dam failure. This type of flooding is rare. The impact of flood in the event of dam failure eg Edgbaston Reservoir in Birmingham, UK is extensive.

Flooding Can Occur Anywhere And Will Get Worse Amount of rainfall over 2 year period. Different areas resulting in different locations that flooding could occur.

SuD’s – Key Queries on Con29DW

SUDS – Planning Stage It makes sense for SuDS to be considered at the planning stage of a development to ensure that amenity, quality and biodiversity assets are included. The Post-legislative scrutiny: Flood and Water Management Act 2010 report recently published by the Environment Food and Rural Affairs (EFRA) has set out a list of recommendations for the next Government. In our SuDS: The State of the Nation 2016 survey, respondents (73%) believed that more standard technical guidance is needed on the long-term maintenance of SuDS. The EFRA report recommends “amending statutory definitions of a sewer to make it easier for Water and Sewerage Companies to adopt SuDS” and “ending the automatic right of new developments to connect surface water discharges to conventional sewerage systems…”

SuDs - Considerations From April 2015 SuDS are required for new major developments* in all cases unless demonstrated to be inappropriate (National Planning Policy Framework). Automatic connection to sewer is no longer accepted. GLA London Plan Policy - insists that development in any of the London Boroughs must reduce their SW run off by a minimum of 50% Property transactions should be informed by understanding the implications of SuDS if future development is proposed. A high level SuDS feasibility report is necessary for property professionals at the initial master planning stage to identify drainage options and risks. *Defined as 10 houses or more or other commercial property development GLA – Greater London Authority

Sustainable drainage (SuDS) and land acquisition “It is highly recommended that pre-application discussions take place before submitting an application to the local planning authority. Ideally, these discussions should start at the land acquisition due diligence stage and continue as part of the pre-planning application process.” L.A.S.O.O. – Local Authority SuDs Officer Organisation

Why are SuDS relevant? Flooding and hence drainage issues are becoming more prevalent. Around 35,000 properties were affected by surface water during the major floods of 2007 (www.gov.uk). Climate change will exacerbate these risks for property owners. Evapotranspiration – Water transferred from land to atmosphere.

Non-statutory technical guidance for SuDS “Where reasonably practicable, for developments which have been previously developed, the runoff volume from the development to any highway drain, sewer or surface water body in the 1 in 100 year, 6 hour rainfall event must be constrained to a value as close as is reasonably practicable to the Greenfield runoff volume for the same event, but should never exceed the runoff volume from the development site prior to redevelopment or that event.” DEFRA, March 2015

What are SuDS? SuDS replicate the natural drainage from the site before development, reducing run-off and flood risk. The SuDS Train, can link swales, basins, wetlands improve water quality, amenity and biodiversity.

How do SuDS work? SuDS mimic the drainage that was there before the development A typical SuDS management train is as follows: Prevention Water Butts Water butts for reusing water, increased grass areas vs hard surfaces

SuDS Management Train Continued Source Control Interception by green roofs and drainage into a permeable pavement or soakaway.

Management Train Conveying Water Drainage of excess water into swales and moved onto storage basins.

Management Train Site Control Detention basins that provide treatment, storage and infiltration or slow release.

Management Train Regional Control The swale network then conveys excess water from several areas to a retention pond at the bottom of the site for final attenuation and treatment.

Infiltration & Retention Basin

Permeable Pavements

Benefits of Suds They can help ‘place making’ to create attractive corridors in developments, connecting people and the environment to water and open spaces. They provide attractive public open space, improve the quality of life and create better communities. They help mitigate and adapt communities to climate change and are able to contain extreme weather events better. They do not need energy or pumping and reduce the demand on existing traditional sewers and downstream water treatment.

Site Analysis: What is the impact? Site layout Site density Construction costs Construction time Maintenance liabilities Future value Neighbouring land Access across the site

NPPF Planning Practice Guidance states National Planning Policy Framework Generally the aim should be discharge surface runoff as high up the following hierarchy of drainage options as reasonably practicable: In Order: Into the ground (infiltration); To a surface water body; To a surface water sewer, highway drain or another drainage system; To a combined sewer.

Understanding SuDS Suitability Knowing site drainage conditions and options for SuDS are key to supporting a property transaction and planning application at Pre- Planning Stage or to address a planning condition prior to permission being granted. Particularly relevant to sites in flood risk areas and for major developments. Protecting a client's commercial interests and asset value. Helps discharge lawyer's duty of care on drainage matters at site acquisition and development. Most Local Authorities have produced a range of SuDS requirements for developers.

What are the risks if SuDS are not assessed? A SuDS condition in your planning permission that could have been shown to be unnecessary. A site which can't be developed because of poor drainage. Unexpected cost, aggravation and loss of time. Duty of care to your client not fulfilled. A damaged client relationship

SuDS Installations Geocellular stormwater storage systems retain Grade II listed park landscaping whilst preventing flooding in Southwark, South London, UK. A £4.28m award-winning flood defence project in Southwark, South London, is combining above and below-ground temporary flood storage to create a pioneering solution at two sensitive and historic parks.

SuDS Installations A long-standing flooding issue for Falkirk Council has been protected from peak rainfall risk with a robust stormwater storage solution from Hydro International that saved space and preserved nearby recreational facilities for local residents.

SuDS Installations The 1900-home Elvetham Heath development at Fleet is hailed as a shining example of sustainable drainage using linked swales and ponds. It is featured in the Government’s seminal Response to the Pitt Review, the forerunner of the Flood and Water Management Act.

Further Information CIRIA ‘The SuDS Manual: http://www.ciria.org/Memberships/The_SuDs_Manual_C753_Chapter s.aspx Old Square Chambers ‘The Role Of Sustainable Drainage Systems’ guidance note: http://geosmartinfo.co.uk/knowledge- hub/downloads/suds-guidance-note/ SUDS VIDEO