This changed the hierarchy of drainage and drainage design considerably and introduced the concept of Sustainable urban Drainage Solutions (SuDS).
In theory, SuDs employ a whole suite of techniques to effectively manage drainage at source. But in reality, SuDS are seen as swales and drainage ditches acting as storm water attenuation ponds. Development of them has been slow with water companies reluctant to adopt them and developers unwilling to waste valuable land installing them. The alternative is below ground storage based on modular tanks or large diameter pipes. Both have advantages and disadvantages:
Above Ground (Soft) SuDS
Ease of construction (generally only earthworks required)
Ease of access for maintenance
Can create a landscaped visual feature
Lower upfront cost
High land take
Potential eyesore and health & safety risk if not maintained or abused. Can be abused by flytippers.
Site topography and conditions can limit functionality
Lack of designer and contractor expertise.
Not conducive for water reuse
Below Ground (Hard) SuDS
Minimises space required
Can use land above
Protected against misuse or vandalism
Recognised design standards
Conducive to rainwater reuse
Water treatment for discharge into water courses requires ancillary components
Greater maintenance expertise required as they are confined spaces
Site conditions can limit functionality (e.g high water table level)
Higher initial cost