Establishing surface water management plans

At the regional scale, surface water management plans should be universally produced to agreed criteria so all development takes account of water management impacts and is bound by appropriate regulation.

Stephen McLaren

The Government’s response to the Pitt review proposes that local authority led surface water management plans (SWMPs) should become a co-ordinating mechanism at regional, sub-regional and local levels. The intention is that the plans will allow authorities to:

• undertake a comprehensive assessment of surface water flooding, as part of their strategic flood risk assessment and predict where it could happen
• make informed land use planning decisions on the basis of such an assessment
• clarify responsibilities and co-ordinate investment in drainage systems to manage the risk more effectively and with greater use of sustainable drainage systems (SUDS)
• improve emergency plans for surface water flooding - this approach is pro-active and risk-based, and therefore delivers resources where they are needed most.

The long-term aim should be to create sustainable drainage infrastructure to allow all city, neighbourhood and site drainage to flow into a natural surface drainage system.

The evaluation of water catchment systems is most appropriate at the sub-regional level. The overall management of water resources can be fully appreciated at the scale at which they operate. Sub-regional opportunities exist for the water infrastructure to operate more as a natural system. This could be through identifying key points in the catchment basin for additional floodwater storage in the landscape or opportunities to introduce large-scale sustainable drainage systems (SUDS).

The information and findings from evaluating the water catchment system can directly inform the evidence base for relevant local development frameworks to ensure appropriate strategies can be integrated into planning policies and guidance.

At the city scale, it’s important to identify and collaborate with key partners to ensure consensus on the approach and priorities for surface water management. Aspects that should be considered at this scale include:

• flood routing through urban areas to be required of new development, redevelopment and as part of retrofit SUDS installation
• the role of conservation and planting of large trees and the use of swales, ponds, lakes and permeable surfacing which allow the water to infiltrate naturally into the ground
• below ground storage systems to be adopted only where silt access is prevented and simple management and inspection can be assured. Wherever possible run-off enters below ground storage through permeable surfaces
• urban watercourses should replace the stormwater sewer wherever possible to provide above ground conveyance of stormwater. This ensures clean water will be generated at source and foul sewers are protected from surcharge. Retrofitting existing roads and public spaces to reduce surface water can have a sizeable effect. Uncontrolled or flash flooding is essentially water in the wrong place and at the wrong time. Sewer flooding occurs when combined (stormwater and sewage) or storm sewers surcharge due to blockage or too much rainfall.
   

Priority: manage surface water and flood risk
Tags: water, regions and subregions, cities and towns