Urban Drainage & Stormwater Management Terminology
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Urban Drainage & Stormwater Management Terminology: LID, SUDS, & WSUD

Global urbanization has brought increased stormwater challenges and made the management of urban drainage systems critically important to cities around the world.  Urban drainage and stormwater management practices have therefore seen considerable change over the years. While urban drainage was once seen only as a problem, the opportunities it presents in additional water supply, increased biodiversity, improved microclimate, etc; are now being widely recognized (Ashley et al., 2013). Consequently, a whole new realm of terminology has been established with the aim of communicating the approaches and benefits of such methods.

The development and use of terminology has come about in an informal manner driven by regional perspectives. The result being that various terms have been used to define similar concepts in different parts of the world. The aim of this article is to explain the reasoning behind certain urban drainage terms we have become accustomed to and shed light on how they came about. More importantly, we seek to clarify the importance of the main terms and what each contributes toward what is increasingly becoming a universal practice.

Low Impact Development (LID)

Most commonly used here in North America, the term low impact development (LID) appears to have been first introduced by Barlow et al. in a 1977 land use planning report from Vermont, USA (Urban Water Journal, 2014). The concept attempts to minimize the cost of stormwater management by taking a “design with nature approach” (McHarg, 1971, cited in Barlow et al., 1977). The term was adopted by other professionals advocating environmentally sensitive planning. This worked to initiate new focus on the increasing need for such systems.

The original intent of LID was to achieve a natural hydrology by use of site layout and integrated control. LID discouraged the previous common practice of large end-of-catchment solutions because of their inability to sufficiently meet expectations. The term LID was used to distinguish the site-design and catchment-wide approach from the common management approach used at that time. The implementation of LID was officially sanctioned in legislation in 2007 in the US and 2010 in Canada. LID has since become a mainstream solution in both the US and Canada.

Sustainable Urban Drainage Systems (SUDS)

The term sustainable urban drainage systems (SUDS) was established in the UK as a way of developing necessary changes to the unsatisfactory urban drainage approaches used at the time. It is understood that Jim Conlin of Scottish Water conceived the SUDS term in 1997 to define the developing stormwater management technology.  In practice, SUDS initially consisted of a variety of techniques that closely replicated the natural, pre-development drainage from a site – the goal being to drain stormwater runoff in a manner that was more sustainable than other conventional solutions being used at the time.

Similar to the principles behind LID, sustainable urban drainage systems are an arrangement of techniques and technologies that work together to form a management train.

Water Sensitive Urban Design (WSUD)

The phrase water sensitive urban design (WSUD) was started in Australia in the 1990’s. WSUD is described as a “philosophical approach to urban planning and design that aims to minimize the hydrological impacts of urban development on the surrounding environment”. Stormwater management is a subset of WSUD directed at providing flood control, flow management, water quality improvements, and opportunities to harvest stormwater to supplement mains water for non-potable uses, (Lloyd et al, 2002).  Due to the fact that the primary professionals advocating the WSUD movement were from within urban drainage community, the initial application in its early years was geared towards stormwater management.

The objectives set out for WSUD included:

  1. Protection and enhancement of natural water systems in urban developments
  2. Integration of stormwater treatment into the landscape by incorporating multiple use corridors
  3. Protection of water quality draining from urban development
  4. Reduction of runoff and peak flows from urban developments by employing local detention measures and minimizing impervious areas, and
  5. Adding value while minimizing drainage infrastructure development costs

Best Management Practices (BMPs)

The term BMP was first coined in the US as part of the Clean Water Act in 1972. It was used throughout North America to describe an approach to prevent pollution and restore a more favorable plant cover and soil structure in order to maintain natural conditions to serve present and future usable water needs. BMPs refer to techniques, measures, or structural controls used to manage the quantity of stormwater runoff and improve its quality through the removal of pollutants. Its goal is to reduce or eliminate the contaminants collected by urban runoff before it transfers into waterways.

The definition of BMPs has since become a more universal term describing best practices related to general pollution prevention.  It encompasses both non-structural and structural attributes – non-structural attributes being operational and procedural practices, while structural attributes refer to engineered or built infrastructure.