Stormwater Management

Traditionally the drainage in built-up areas is managed through conventional underground pipe systems. Such systems are designed to prevent local flooding by conveying water away as quickly as possible downstream of a development. This alteration in the natural flow of drainage can however lead to pollution problems within catchments e.g. when it rains, the stormwater flows pick up pollutants and washes these into rivers and streams. Rapid and increased stormwater runoff can also cause downstream flooding, localised erosion, destroy habitats and contribute to combined sewer overflows (CSOs). Furthermore, traditional engineered systems are not always designed with wider social considerations in mind, such as amenity, aesthetics and biodiversity.

It is now recognised that continuing to implement conventional drainage systems in urban areas and ignoring wider issues is an unsustainable long-term option. It does not always make economic sense to use conventional underground pipe systems as these have only limited appeal and can add to existing problems.

The solution is sustainable stormwater management.

Government Departments are currently being driven by a range of legislation and policy which is driving the implementation of Stormwater Management in Northern Ireland. This includes the EU Water Framework Directive (2000/60/EC); the EU Habitats Directive (92/43/EEC); the EU Freshwater Fish Directive (78/659/EEC); the EU Urban Waste Water Treatment Directive (78/659/EEC); the EU Waste Water Treatment Directive (78/659/EEC); the European Directive on the Assessment and Management of Flood Risk (2007/60/EC); the Northern Ireland Sustainable Development Strategy and various Planning Policy Statements. Under this legislation and policy, Government must manage and put into place interventions and control measures to manage water resource pressures more effectively. It is now widely accepted that the solution to the problems the island as a whole is experiencing is sustainable stormwater management.

Sustainable stormwater management is the generic term for a range of techniques which seek to deal in an integrated way the issues of water quantity, quality and amenity. Basically, these measures try to mimic natural wetland features to counter the impacts of increased urbanisation and coverage of impermeable surfaces. It is now accepted within the UK that the construction costs associated with the design and installation of sustainable stormwater solution are generally lower than that of conventional systems. Other benefits of sustainable stormwater management include:

• Management of run-off flow rates, reduction of peak flow and an increase in pipe capacity to lower flood risks
• Reduction of the impact of urbanisation and the danger of flooding
• Provision of water treatment, protection of water resources from point and diffuse pollution
• Protection of water and air quality
• Reduction of stormwater treatment costs and sewage treatment costs, as well as lowering hydraulic leading
• Improvement of aesthetics and urban amenity as such systems are integrated into the environment as usually attractive features
• Improvement in biodiversity, providing a new habitat for wildlife that would otherwise be scarce in the built environment, and,
• Promotion and engineering of increased groundwater recharge

"Managing Stormwater - A Strategy for Promoting the Use of Sustainable Drainage Systems (SuDS) within Northern Ireland" was published by the Northern Ireland Environment Agency (NIEA) in September 2011. A Stormwater Management Group (SMG) was set up to take forward recommendations from the Strategy Document. The SMG is an inter-departmental policy coordination and implementation group, jointly chaired by Northern Ireland Environment Agency (NIEA) Water Management Unit (WMU) and Department for Regional Development (DRD) Water Policy Division. The fundamental aim of the SMG group is to examine a range of approaches to develop more integrated stormwater management in Northern Ireland.