Sustainable Urban Drainage Alan Jones (Alan.Jones@ed.ac.uk)

Sustainable Drainage A concept that focuses on the environment and people. Considers: Quantity of runoff Quality of runoff Amenity value of surface water Existing urban drainage systems are: Unsustainable in the long-term Damaging to the environment

Why are SUDS needed? Hydrograph: SUDS: Discharge Peak discharge becomes larger Discharge Time Floods occur quicker due to reduced infiltration SUDS: Attenuate flow Promote infiltration & groundwater recharge

Why are SUDS needed? 11% of Scottish river length is classified as polluted due to contamination from urban drainage SUDSWP (2000) SUDS aim to protect watercourses from point/diffuse pollution by acting as sinks for contaminants Cost implications for maintaining long-term performance of SUDS

Why are SUDS needed? Amenity A ‘loaded term’ when used in relation to SUDS – environmental/community issues Covers: Aesthetic & Ecological quality of the landscape Land-use Wildlife habitats Land-values Recreation opportunities Educational opportunities Water-resources Other factors: Opportunity costs Perceptions of risk Construction impact

SUDS ‘Triangle’

Present Legal Status WFD – Water Framework Directive (2000) Prevent deterioration in water status Restoration of surface waters to good ecological and chemical status by 2015 Reduction of pollution from priority substances Contributing to mitigating the effects of floods and droughts Preventing/limiting pollution input into groundwater CAR – The Water Environment (Controlled Activities) (Scotland) Regulations (2005) Surface water-runoff in areas constructed, or construction sites operated, after 1st April 2006 must now be drained by a Sustainable Urban Drainage System Exceptions – Single dwellings or if the discharge is to coastal water

Conventional Drainage Precipitation: Rainfall/Snow Rapid conveyance of water & pollutants Local watercourse

SUDS Drainage: The ‘treatment train’ approach Connect SUDS together Individual function of local SUDS techniques beneficial – but design should be led by a holistic vision & approach Combined integrated function – mimics the waterflows in the natural hydrological cycle: Surface Flow Infiltration Storage in water-bodies Interflow Evapotranspiration

Treatment Train Good Housekeeping: best practice to eliminate, or minimise, pollutants being generated and allowed into the environment. Source Controls: methods of dealing with runoff at source, e.g. permeable paving, filter strips, or roadside filter trenches. Site Controls: local controls that deal with generally smaller catchment areas, e.g. detention basins. Regional Controls: larger components that might typically deal with larger catchments and upstream site controls, e.g. stormwater wetlands and retention ponds. (Heal, 2004)

A variety of techniques Drainage conveyance Kerb design Roof drainage reuse Detention Basins Filter Drain Swales

Falkirk Stadium Retention Pond (Undeveloped catchment) Retention Ponds Falkirk Stadium Retention Pond (Undeveloped catchment)

Retention Ponds / Wetlands Lidl Distribution Centre, Livingston - Retention Pond (Loading bay, Carpark runoff)

Tackling Contaminants The flood-reducing benefits of SUDS are obvious... Store water at various points in the catchment and allow water to be re-used, infiltrated, released slowly and/or evaporated. These processes also allow the trapping of potential contaminants (e.g. metals, PAHs/Hydrocarbons) within the treatment train. Contaminants are typically adsorbed (physico-chemically bonded) to sediment particles that are entrained in flow. As water speed is slowed down using SUDS, particles (and therefore contaminants) settle out.

Contaminant Sources: Vehicles 15-fold increase in the number of car and taxi miles covered over the last 50 years! SUSTAINABLE (?) Campbell et al. (2004)

Land-Use & Contamination Vehicles Pavement Surface Debris Brakes Tyres Frame & Body Fuels & Oils Concrete Asphalt De-icing Salts Litter Cadmium (Cd) Chromium (Cr) Copper (Cu) Iron (Fe) Lead (Pb) Nickel (Ni) Vanadium (V) Zinc (Zn) Chlorides Organic Solids Inorganic Solids PAHs Phenols (Beasley and Kneale, 2002)

Design - Site Constraints Physical site constraints can make construction difficult or impossible, and maintenance expensive if not addressed adequately. Factors to consider include: topography - e.g. steep slopes soils and geology - e.g. erosivity, porosity, depth to bedrock or instability groundwater - e.g. geochemistry and water table depth space - limited open space, proximity to underground services. (e.g. gas, power) Social constraints include issues of health and safety, aesthetics and impacts on recreational facilities. Factors to consider include odour problems visual impacts noise physical injury - resulting from unauthorised access to structures; contamination - infection, poisoning or injury caused by trapped pollutants or algal blooms vermin - e.g. mosquitoes, rats.

Design – Maintenance Issues Not only can a poorly maintained SUDS technique function ineffectively, it can become a source of pollution or flood hazard itself. When designing a SUDS measure, the following points should be considered: ease of maintenance and operation - the selected treatment should be easy and safe to maintain and operate extent of maintenance - ensure the maintenance requirements are within the operator's capability access to the treatment site - consider the ease of site access, when reviewing the treatment's maintenance requirements frequency of maintenance - ensure that resources are available to carry out maintenance at the required frequency debris and pollutant clearing - during clearing, the treatment should not require direct human contact with debris and trapped pollutants (automated clearing options are preferred) disposal - consider the disposal requirements of any waste from the treatment process.

Case Study: J4M8 SUDS development (c. 2000) Previously agricultural land Now a distribution hub based mid-way between Edinburgh and Glasgow

J4M8 Oblique Aerial Photograph M8 Motorway Phase 1 Retention Pond Reddinghill Bing (Landscaped, but still burning) Aldi Distribution Centre Former Scottish Courage Distribution Centre