Urban areas place pressure on catchment management through sewer networks, diffuse urban runoff, and other facilities. Sewer networks can cause combined sewer overflows and pollution through leakage. Better monitoring is needed to understand spill frequencies. Solutions include adding sewer capacity, separating networks, and using source control. More stringent standards are being considered in the EU. Sustainable approaches include integrated catchment modeling to proactively address events, and surface water management plans to promote sustainable drainage systems. Diffuse urban runoff from roads and other surfaces pollutes waterways. Control measures include sustainable drainage retrofits, spill regulations, traffic controls, public awareness, and using sustainable drainage for new development.

1. Catchment
Management
Urban Pressures

2. Urban Pressures
• Sewer Networks
• Diffuse Urban runoff
• Transport facilities
• Amenity Spaces
• Industrial facilities and
contaminated land
• Waste transfer and disposal
facilities
• Commercial Activities

3. Sewer Networks
• Combined Sewer Overflows
• Leakage/exfiltration
• Key issues with respect to sewer network
• Better understanding of spill frequency required
• 70% of rivers with CSO discharges had unknown
spill frequency in 1st RBM cycle

4. Measures - Sewer network
 Addition of extra capacity
 Screening of spill volumes – does not address degradation of
receiving water body
 Separation of network and rehabilitation of sewers where cost
effective
 Use of source control
– Limited on existing development (retrofitting not always possible
– Introduced through new development

5. Improving standards
• EU considering more stringent frequency spill
standards
• Better understanding required but likely that
significant investment required (e.g. Scottish
Water estimate £14 billion)

6. More Sustainable Solutions
• An understanding of the network and treatment process in real time through a
fully telemetered network is key.
• Then through the application of “next generation” integrated catchment
modelling build the capability to forecast and deal proactively with potential
events before they occur.
• Integrated Catchment Drainage Plans (Scottish Water) and Surface Water
Management Plans (United Utilities) are key to the sustainable management
of flooding and pollution of surface waters.
• The development of SuDs could be promoted through Surface Water
Management Plans and collaboration with relevant statutory and planning
authorities.

7. Diffuse Urban runoff
• Runoff from roads - sediment often contaminated with toxic
metals from vehicle break linings and other components.
• Salt from winter gritting can also act as a pollutant,
• Oil leaked from vehicles.
• PAHs from combustion, discharged from vehicle exhausts and
also accumulate on roads and other urban surfaces, from
which the contaminants are washed off into the drainage
system.

8. Diffuse Urban pollution - Control Measures
• Sustainable Urban Drainage Systems (SUDS) retro-fits for worst local source
areas of contamination. SUDS retro-fits are most likely to be effective if a
treatment train approach is used.
• Managing risks of accidental spills of oil and chemicals in commercial and
industrial areas by enforceable housekeeping regulations.
• Traffic control (reduction) measures to minimise pollution loads on urban
watercourses and drainage systems.
• Public support and awareness raising to curtail individual polluting practices
• Effective application of SUDS technology for new development to prevent
urban pollution becoming an even larger problem.