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Drainage Systems - SuDS

holistic approach to water management. There is a lot to learn from our international colleagues particularly in Australia and the USA on Water Sensitive Urban Design (WSUD), the process of integrating water cycle management into urban planning and design. We still have a way to go before we see a transition in the UK to a WSUD approach. It was evident from the conference that if we are to effectively address the issues presented by climate change, urban creep, energy and carbon, the Water Industry will require new and smarter ways of managing surface water management. This can only be achieved through a long term integrated approach involving partnership working and early community engagement.

The conference took place on 27th June 2012 at SOAS, University of London. Outputs from the event including speaker presentations are freely available on the CIWEM websites. CIWEM has also published briefing reports on Integrated Water Management and Multi-Functional Urban Green Infrastructure

Working for the public benefit for a clean, green and sustainable world, CIWEM (The Chartered Institution of Water and Environmental Management) is the only

independent, chartered professional body and registered charity with an integrated approach to environmental, social and cultural issues. To find out more about the institution visit

CIWEM organises a multitude of conferences and events bringing together a diverse audience of environmental professionals, regulators, academics, researchers, local authorities, NGOs, civil servants and others to debate, share knowledge, hear from and engage with key figures in the environment sector, and network. These events support CIWEM's policy work and inform key initiatives such as the CIWEM manifesto, briefing reports, policy statements, lobbying and other work. See the CIWEM Events Calendar for a list of future events.


Defra & LGA Flood Portal:

CIWEM Conference Presentations: outputs.aspx

Integrated Water Management link

Multi-Functional Urban Green Infrastructure CIWEM Events Calender calendar.aspx

Manage Storm and surface water with ISIS FAST

ISIS FAST is an innovative flood inundation modelling tool designed to allow quick assessment of flooding using simplified hydraulics. It provides the functionality to carry out surface water modelling at strategic, intermediate and detailed levels and provides results in seconds or minutes as opposed to hours or days, which is up to 1,000 times faster than traditional two-dimensional models.

Surface water management plans outline preferred surface water management strategies for a Lead Local Flood Authority (LLFA) area, and are undertaken with key local partners, led by the local authority. ISIS FAST can help partners to map surface water flooding, understand its impact, and visually communicate the risk to stakeholders.

ISIS FAST is fully integrated with ISIS suite and links with other modelling and analysis tools to deliver a powerful but easy to use surface water mapping system. ISIS FAST is a new way of mapping flood

risk quickly, while still representing the most important topographic affects that control patterns of flooding. ISIS FAST combines ground elevation data with rainfall amounts to model water depths in topographic depressions, as well as the pathways between them. ISIS FAST captures the most important features of flooding, without the need for time consuming model setup, long run times or as much modelling expertise when compared to building traditional 1D and 2D models.

Why use ISIS FAST for surface water management plans?

ISIS FAST provides a cost effective way of rapidly delivering flood information for all levels of analysis, from strategic to detailed. It has been extensively benchmarked against full two-dimensional (2D) models to ensure it captures the key behaviour of surface water flooding. It is used throughout the world as a key analysis tool for surface water management. ISIS FAST uses a two stage approach: first, topographic analysis is used to extract surface water catchments and pathways; and second, a "wet" method is used to route water between these catchments. ISIS FAST is therefore even faster when multiple scenarios (storm probability, runoff hydrology, sewer capacity and climate change) are to be run. Using a "wet" method means ISIS FAST outputs are more realistic and informative than other approaches like the "rolling ball" method, and allow the effect of different rainfall and runoff hydrology scenarios to be investigated.

Key Features

• ISIS FAST is fully integrated with the ISIS suite, allowing users to easily switch between the FAST and full two-dimensional hydrodynamic solvers

• it produces results up to 1,000 times faster than full two- dimensional modelling methods

• links with ISIS Mapper (a free GIS tool) and other software developed by Halcrow for easy mapping and analysis functions • rapid model development – from digital terrain model (DTM) to outputs in only five minutes

• outputs grids of flood extent and depths, with ISIS Mapper functionality to produce vector flood extents • even quicker to run multiple effective rainfall scenarios once topographic analysis is done

• pathway flooding represented with user control over depths and extents

• used in conjunction with more detailed modelling software, such as ISIS Professional and ISIS 2D

• reduces the cost of subsequent detailed modelling by identifying the flood risk hot spots where detailed analysis is needed • can test solutions that protect people, property, critical infrastructure and the urban environment

ISIS FAST’s computational efficiency allows users to generate a Monte Carlo ensemble of thousands of simulations. Modellers can use this to explore the uncertainty arising from key hydrological parameters in a fully probabilistic framework.


By Vijay Jain, Halcrow

National pluvial flood map for Scotland

ISIS FAST has been used to map surface water flooding across the whole of Scotland, covering an area of 78,000 km2 split into 4,000 models. Using ISIS FAST, the whole of Scotland could be modelled in 48 hours per rainfall scenario. Flooding in Loch Achray St, Glasgow.

ISIS FAST outputs were validated using historical records of flooding in Glasgow in 2002, and outputs from detailed level integrated surface-sewer model developed for the Glasgow surface water management plan. The validation results confirmed that ISIS FAST produced useful, credible results at national and regional scale.

Surface water flood mapping, London

ISIS FAST has been used to map surface water floodinginEastLondon. Comparedwithresults delivered by an ISIS 2D (full hydraulics) model for the same area, ISIS FAST was able to reproduce flood extents and depths to within 10cm, but 1,000 times more quickly.

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