Legislation and drivers

Sustainable Urban Drainage is now part of legislation and is a critical part of planning. Blue roofs form part of the options available for SuDS.

The Flood and Water Management Act 2010 was introduced in England and Wales and implemented to better manage flood risk. The Act creates safeguards against rises in surface water drainage charges and protects water supplies for consumers. The Act gives levels of responsibility to local authorities to co-ordinate flood risk management in their area.

Many local planning authorities (LPAs) are adopting early perspectives that encompass Schedule 3 of the Act to bring in measures that prevent flooding. Within construction and development, planners are restricting the amount of rainwater leaving a site via the drainage system, limiting water egress to 5-10 litres per second per hectare, the same flow rates for regional greenfield sites.

The Environment Agency and lead local flood authorities provide data and flood maps to assist drainage engineers and architects identify the level of risk by categorising the possibility and hazard levels of flooding by zones. The zones are:

Flood Zone 1 – low probability, where land has a less than 1 in 1,000 annual probability of river or sea flooding.

Flood Zone 2 – medium probability, where the land has between a 1 in 100 and 1 in 1,000 annual probability of river flooding; or between a 1 in 200 and 1 in 1,000 annual probability of sea flooding.

Flood Zone 3a - high probability where land has a 1 in 100 or greater annual probability of river flooding; or having a 1 in 200 or greater annual probability of sea flooding.

Flood Zone 3b - classifies functional floodplains where land is identified to receive waterflow to be stored in times of flood. Local planning authorities should identify in their Strategic Flood Risk Assessments areas of functional floodplain and its boundaries accordingly, in agreement with the Environment Agency.

Flood zones 2 and 3, have water discharge management implications with zone 3 having the strictest regulations and will be subject to levels of flood defence and discharge management resulting in the type of construction permitted. The Government publishes information and advice on how to take account of and address the risks associated with flooding and costal change in the planning process.