Issues associated with catchment management in urban areas and the development of sustainable urban drainage systems (SUDS).
The need for sustainable drainage
Changes to drainage systems in urban areas occurred because of the need to channel water away from vital and expensive industry and housing. In the past little thought was given to the ecological impact of these changes and to the COST of taking such actions. Many rivers were straightened or channelised, or put into tunnels under the ground as culverts, or ponds and lakes drained without a thought for the longer-term consequences of those actions. Increased urban flooding as a result of using impermeable surfaces is also a major problem.
In the 20th Century hard engineering was used with the goal of drainage systems being FAIL SAFE, this is a design feature that in the event of flood failure, inherently responds in a way that will cause no or minimal harm to other equipment, the environment or to people. Many old concrete flood channels in urban areas were designed this way. Channelisation was often involved, a method of river engineering that widens or deepens rivers (and often uses concrete) to increase the capacity for flow volume at specific sections of the river. Used in urban areas to reduce flooding. An example of this is the Los Angeles River, which flows through a concrete channel on a fixed course, which was built after a series of devastating floods in the early 20th century. 1
The Los Angeles River receiving the Tujunga Wash (right) near Colfax Ave. in Studio City, California. View is to the west
by Junkyardsparkle [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons 2
The value of sustainable drainage
Drainage systems have an amenity value to people and cities, this means that they have value in terms of water resource management, provision of habitat for wildlife, recreational value for people, community facilities and even in moderating urban climates. Water quality is also regulated and moderated by drainage systems, and this is seen as an increasingly important aspect of urban drainage systems. Now, in the 21st century, urban planners are paying far closer attention to the environmental and sustainability aspects of any changes they make to natural drainage systems in urban areas.
There are 2 major areas to consider;
Some of the major issues associated with the management of urban catchments include:
To combat these issues urban planners are moving towards Sustainable Urban Drainage Systems (SUDS). The idea behind SUDS is to try to replicate the drainage patterns of natural systems by using cost-effective solutions with low environmental impact to drain away dirty and surface water run-off through collection, storage, and cleaning before allowing it to be released slowly back into the environment, such as into water courses. This is to counter the effects of conventional drainage systems that often allow for flooding, pollution of the environment – with the resultant harm to wildlife – and contamination of groundwater sources used to provide drinking water. These SUDS provide ecosystem services, which are benefits obtained from the regulation of ecosystem processes, in this case urban river systems, such as climate regulation, flood regulation, water purification and waste management, pollination or pest control.
Swale at Newcastle Great Park with reeds
The principles of SUDS solutions should be a drainage system;
Examples of SUDS
NEXT TOPIC - River Restoration and Conservation
1- The River Project - The Los Angeles River. Accessed 12th January 2020 from https://www.theriverproject.org/learn/the-los-angeles-river-watershed
2- Junkyardsparkle [CC BY-SA (https://creativecommons.org/licenses/by- sa/3.0)] Accessed 12th January 2020 from https://commons.wikimedia.org/wiki/File:L.A._River_Tujunga_Wash_under_Colfax.jpg
3- Department for environment, food and rural affairs (2012) Tackling water pollution from the urban environment. Accessed 11th January 2020 from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/82602/consult-udwp-doc-20121120.pdf
4- Susdrain (2020) – SUDS principles - Accessed 11th January 2020 from https://www.susdrain.org/delivering-suds/using-suds/suds-principles/suds-principals.html
5- Essex County Council (2020) What are sustainable drainage systems (SuDS)? Accessed 11th January 2020 from https://flood.essex.gov.uk/new-development-advice/what-are-sustainable-drainage-systems/
Posted by Rob Gamesby April 2020