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:

Floods occur quicker due to reduced infiltration

Peak discharge becomes larger

Time

Dis

char

ge

SUDS:

• Attenuate flow

• Promote infiltration & groundwater recharge

Industrial Effluent, 2.1%

Contaminated Land, 1%

Others, 2.7%

Urban Drainage,

11.4%

Acidification, 11.7%

Agriculture (Diffuse

Sources)26.2%

Sewage Effluent, 33.9%

Agriculture (Point Sources)

6.3%

Mine Drainage 8.9%

SUDSWP (2000)

Why are SUDS needed?

• 11% of Scottish river length is classified as polluted due to contamination from urban drainage

• 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

1. Good Housekeeping: best practice to eliminate, or minimise, pollutants being generated and allowed into the environment.

2. Source Controls: methods of dealing with runoff at source, e.g. permeable paving, filter strips, or roadside filter trenches.

3. Site Controls: local controls that deal with generally smaller catchment areas, e.g. detention basins.

4. 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

Kerb design

Filter Drain

Roof drainage reuse

Swales

Drainage conveyance

Detention Basins

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!

Increase in Traffic MilesCar and Taxis

0

50

100

150

200

250

300

1950 1960 1970 1980 1990 2001

Year

Bil

lio

n v

eh

icle

mil

es

Campbell et al. (2004)

SUSTAINABLE (?)

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.

• SUDS development (c. 2000)• Previously agricultural land• Now a distribution hub based mid-way between

Edinburgh and Glasgow

Case Study: J4M8

J4M8 Oblique Aerial Photograph

M8 Motorway

Phase 1 Retention Pond

Reddinghill Bing (Landscaped, but still burning)

Aldi Distribution Centre

Former Scottish Courage Distribution Centre