Surface Water Drainage Basics For New Developments

Understanding Surface Water Drainage

Surface water drainage is the process of managing rainwater and runoff from roads, roofs, and other impervious surfaces. Effective surface water drainage design is critical for residential developments, ensuring that water is managed efficiently to prevent flooding, protect property, and promote environmental sustainability.

Effective surface water drainage design is crucial for the success and sustainability of residential developments. While conventional drainage systems offer efficiency and reliability, SUDS provide significant environmental benefits and promote a sustainable approach to water management.

Policy

The UK government has implemented several policies and guidelines to promote the use of Sustainable Urban Drainage Systems (SUDS) in urban development. These policies aim to manage surface water runoff sustainably, reduce flood risk, enhance water quality, and support biodiversity. Refer to the National Planning Policy Framework (NPPF), The Flood and Water Management Act 2010, Planning Practice Guidance (PPG) and Non-Statutory Technical Standards for Sustainable Drainage Systems(DEFRA).

The first requirement for surface water drainage by Planning Authorities and Utility companies is SUDS prior to considering  conventional drainage, even then its typically a combination of SUDS element with conventional drainage system.

Basic Principles of SUDS

The key principle of SUDS is to manage storm water at source towards flood risk management first and to create other benefits to the community and environment.  This takes the form of managing the following four pillars of SUDS as set out in CIRIA C753 SUDS Manual :

• Water quantity
• Water quality
• Amenity
• Biodiversity

Water quantity is mainly managed by attenuation, harvesting or infiltration solutions. Natural means of managing water quality in most cases includes green infrastructure which also improves amenity and, in some cases, create opportunities for improving biodiversity of the site.

Key Features of SUDS in Residential Development :

• Permeable Surfaces: Utilises materials like permeable paving to allow water infiltration into the ground or attenuate below ground either via aggregate void storage or container storage.
• Swales and Basins: Shallow, vegetated channels and basins that slow down water flow, promoting infiltration, reducing runoff and promoting biodiversity.
• Green Roofs: Roofs covered with vegetation that absorb rainwater, provide insulation, reduce runoff and promote biodiversity.
• Rain Gardens and Bioretention Areas: Landscaped areas designed to absorb and filter rainwater, enhancing groundwater recharge and supporting biodiversity.
• Storage containers for attenuation purposes, this could be in the shape of underground tanks and SUDS crates and other storage options for storing surface water for reuse such as water butts and rainfall harvesting systems.

Conclusion

The UK government and Local planning authorities policy on surface water drainage focuses on sustainable and integrated approaches to manage surface water runoff, mitigate flood risks, and enhance environmental quality. By adhering to these policies and guidelines, developers and planners can create resilient, sustainable urban environments that effectively manage surface water.

Contact SANDS for detailed advice and support on surface water drainage design for residential developments and flood alleviation schemes.

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