New IUD Modelling Guide Goes Live
Fiona Dow of Mayer Brown co-authors new industry guide on Integrated Urban Drainage modelling.
WaPUG the Urban Drainage group of CIWEM, the Chartered Institute of Water and Environmental Management have published a technical guide for hydraulic modellers on the relatively new field of Integrated Urban Drainage Modelling. Mayer Brown’s Fiona Dow co-authored the modelling methodology chapter.
Integrated Urban Drainage (IUD) is an approach to planning or managing an urban drainage system which leads to an understanding of how different physical components interact and how different organisations must work together for it to operate effectively.
In its widest meaning IUD considers all the aspects of an urban drainage system which contribute to water quality and flooding problems (e.g. diffuse pollution, combined sewer overflows (CSOs), pumping stations (wastewater and storm water), sewage treatment works (STWs), receiving water impacts). However, in the context of this WaPUG IUD modelling guide our meaning is restricted to the narrower consideration of surface flooding, reflecting the concern of Government to develop a more holistic approach to managing flood risk in urban areas. Hence, this document provides best practice guidance on how to model the interaction of different components to improve understanding of urban flood risk. Surface flooding may originate from any component of the urban drainage system; and this guide focuses on that flooding caused by interactions between different drainage components.
Although applicable across a range of situations, IUD modelling has a particular role in supporting the development of Surface Water Management Plans (SWMP). In February 2008 the UK Government’s Future Water strategy for England and Wales proposed that SWMPs will be a new vehicle through which urban flooding will be assessed and resolved in the future within England and Wales. The position is similar in Scotland, whereby it is envisaged that SWMPs will be a key element of the implementation of the Flood Risk Management (Scotland) Bill. Formal SWMPs were developed through the Defra IUD pilot projects3 in 2007/8 and promoted in Sir Michael Pitt’s review of the July 2007 floods (Pitt, 2008).
The first SWMPs will be developed in England and Wales through 2009 following guidance published by Defra in January 2009 (Defra, 2009). The Defra guidance sets out a framework within which local partnerships (local government, water companies, the Environment Agency and others) first seek to understand surface water flood risk and then plan a practical, sustainable and cost effective series of measures to reduce it. IUD modelling will be central to the risk assessment (stage 2) and options (stage 3) components of the SWMP framework.
Other applications for an IUD modelling approach include:
- Detailed analysis of the cause, effect and remedy of sewer flooding
- Improved understanding of the impact of watercourse interactions on sewer system performance and the operation of CSOs, pumping stations and other sewer assets
- Development of integrated flood risk plans for essential infrastructure and utility assets
- Strategic Flood Risk Assessments
- Detailed Flood Risk Assessments
- Development of emergency response plans
- Understanding pollution impacts on receiving waters (e.g. Urban Pollution
- Management (UPM) Studies)
- Climate change adaption and carbon reduction strategies (reduced energy use)
IUD modelling is a relatively new field and is not as well developed as its constituent parts such as sewer modelling or river modelling in their own right. However, it is the logical progression of the more established constituent parts. IUD modelling also encompasses the relatively new technique of overland surface water modelling (major system) involving either one-dimensional (1D) or two-dimensional (2D) flow routing models.
The guide illustrates how different modelling approaches can be applied in different circumstances. Many software alternatives are available, but the guide considers generic approaches rather than specific products. The focus is on modelling within a context that is consistent with broader methodologies for SWMPs, Flood Risk Assessments (FRAs) and Drainage Area Studies or Plans (DAS / DAP) etc.
For further information, and a copy of the guide visit http://www.ciwem.org/groups/wapug/modelling.asp