5. Improved flood risk management through advances in rainfall modelling, experimental evidence, and catchment and urban modelling
Submitting Institution
Imperial College LondonUnit of Assessment
Civil and Construction EngineeringSummary Impact Type
EnvironmentalResearch Subject Area(s)
Earth Sciences: Physical Geography and Environmental Geoscience
Agricultural and Veterinary Sciences: Other Agricultural and Veterinary Sciences
Engineering: Environmental Engineering
Summary of the impact
Our research and resulting impacts extend across a wide range of
flooding problems, from localised urban floods to river bas in flooding.
The under pinning research ranges from extending the evidence base, to
improved rainfall estimates, and to advances in hydrological and hydraulic
models. The impact of our research has been through the creation and
application of new methodologies (e.g. AOFD) and software tools (e.g.,
TSRSim) for the design and analysis of flood management systems in the UK
and internationally, via joint projects with consulting engineering
companies, and through the influence of our research on national and
regional policies towards improved land use management practices (e.g.,
Glastir, Wales).
Underpinning research
Our research in flood risk management has addressed two major gaps in floods
science: the lack of evidence and under standing about factors affecting
flood flows; and the lack of numerical models to help convert understanding
into decisions. Since its inception in 1993, this programme of research has
i nvolved a number of academics including H. Wheater (1993-2010), N.
McIntyre (1999-2013), C. Maksimović (1997-2013); C. Onof (1995-2013), N.
Bulygina (2007-13) and D. Butler (1993-2005).
Three as pects of this
research have led to major impact and are summarized here: (a) rainfall
modelling; (b) land use management and (c) urban pluvial flood modelling.
2.1 Rainfall modelling
Traditional flood design using design events relies upon unrealistic
assumptions about rainfall. Our programme of rainfall research has
provided the bas is for improvements using continuous simulation of
rainfall. Building on fundamental research into stochastic rainfall
modelling from 1993-2002 Onof and Wheater subsequently (2002-05) developed
new methods for generating daily rainfall simultaneously at a number of
sites while maintaining its complex space-time properties, including the
ability to synthesise extreme rainfall [1]. This was achieved by
developing techniques based on point process and generalised linear
models. This Defra funded research was extended (2005-2006) to adapt the
method so that it can estimate space-time rainfall under climate change.
In a third aspect of the work, based on continuous studies since 1993,
Onof has developed methods for the downscaling of daily rainfall to
high-resolution (e.g., hourly or 5-minute) rainfall, to provide a unique
ability to simulate bursts of rainfall, including under climate change,
thus, in particular, meeting the needs of urban drainage design [2].
Together, these elements of underpinning research led to the software
packages, HYETOS, GLIMCLIM, and TSRSsim, which have been widely used by
consultants and government agencies during 2008-2013 (see section 4).
2.2 Land use management
There is widespread speculation that reverting towards a more natural
rural landscape will reduce downstream flood risk, and there is major
interest and activity in UK government in implementing "natural flood
management". However, prior to our series of RCUK funded research projects
in the period 2004 -2012, there was insufficient evidence and methods to
evaluate the efficacy of such "natural" approaches. From our sets of
experimental sites at Pontbren, Wales ( 2004-2012), Wheater, McIntyre and
Bulygina produced evidence of the links between soil type, land management
and flood flows; and how upland land management can (and cannot) be used
to control floods; and how it can also provide other environmental
benefits as part of agri-environment schemes [3,4]. Furthermore, so that
scenarios of change can be assessed in terms of flood risk and as sociated
costs and benefits for arange of catchments, we developed new
generalisation and upscaling techniques [4]. This modelling research
programme is providing an evolving national capability for continuous-time
simulation of floods, leading in 2004-2012 to the focus on solving the
"natural flood management" question.
2.3 Urban pluvial flood modelling
For the urban environment, Maksimović and Butler have conducted research
that has promoted the use of physically based approaches to improve models
of urban pluvial flooding, and to reduce the uncertainty in the spatial
and temporal modelling. From 1999-2009, our research into processing of
digital terrain data led to improved automatic delineation of flood-prone
areas in urban catchments and the development of our Automatic Overland
Flood Delineation (AOFD) method [5]. Research from 2004-2012 produced new
methods for 1D/1D urban flood modelling suitable for real time
applications, incorporating the AOFD method [6]. These latter two items of
underpinning research produced the predecessors to the modern commercial
models for urban pluvial flood modelling (see section 4).
References to the research
(*References that best indicate quality of underpinning research)
*[1] Wheater H.S., Chandler R.E., Onof C., Isham V.S., Bellone E., Yang
C., Lekkas D., Lourmas G. and Segond M-L. (2005) `Spatial-temporal
rainfall modelling for flood risk estimation', Stochastic
Environmental Research and Risk Assessment 19(6) pp 403-416,
doi:10.1007/s00477-005-0011-8.
[3] Marshall M.R., Francis O.J., Frogbrook Z.L., J ackson B.M., McIntyre
N., R eynolds B., Solloway I, Wheater H.S., and Chell J. ( 2009) `The
impact of upland land management on flooding: Results from an improved
pasture hillslope Hydrological Processes' (2009) 23(3) pp
464-475, doi:10.1002/hyp.7157.
*[4] Bulygina N., McIntyre N., Wheater H. (2009) `Conditioning
rainfall-runoff model parameters for ungauged catchments and land
management impacts analysis' Hydrology and Earth System Sciences 13(6)
pp 893-904, doi:10.5194/hess-13-893-2009.
*[5] Maksimović Č., Prodanović D., Boonya-aroonnet S., Leitão J.P.,
Djordjević S. and A llitt R. (2009) `Overland flow and pathway analysis
for modelling of urban pluvial flooding'. Journal of Hydraulic
Research 47(4) pp 512-523,
doi:10.1080/00221686.2009.9522027.
[6] Leitão J.P., Simões N.E., Maksimović Č., Fer reira F., Prodanović D.,
M atos J.S. and Sá Marques A. (2010) `Real-time forecasting urban drainage
models: full or simplified networks?' Water Science and Technology
62(9) pp 2106-2114, doi:10.2166/wst.2010.382.
Research Grants and Funding
A significant part of the under pinning research was carried out through
our membership of the National Flood Risk Management Research Consortium
(FRMRC 1&2) funded by EPSRC, NERC, EA, Defra, and others, during
2004-2012. EP/F020511/1. FRMRC 1&2 has been the largest UK research
programme on flood risk science in recent years and within both phases we
led the land use management part of the programme.
Details of the impact
Our floods research has had substantial impacts on floods policy and
design practice, and on attitudes and unde rstanding of flood risks
olutions by audiences ranging from land owners to national governments.
These impacts extend across all components — rainfall modelling,
experimental evidence, and catchment and urban modelling.
4.1 Rainfall modelling
Research into rainfall modelling has led to the development of tools for
hydrological and drainage system design using continuous simulation rather
than single design events, a development encouraged by the Environment
Agency. The software tool HYETOS for hourly rainfall generation,
originally de veloped as part of a 30% /70% ICL/NTUA Athens collaboration,
is downloaded on average 140 times per year in particular by consultants
in the water industry. GLIMCLIM is a spatial daily rainfall generator
originally developed as part of a 50%/50% Imperial/UCL collaboration,
which Halcrow has used in projects with total benefit of about £15K, and
are investing £5K in developing a user interface for.
For urban drainage applications, the software tool TSRSim, based entirely
upon work by Onof, has been developed at a cost of over £20,000 by HR
Wallingford Software in 2005 in collaboration with Onof [A]. It has been
purchased by a number of consultancies and water companies (e.g. MWH,
B&V, Yorkshire Water, United Utilities and Southern Water) at a unit
cost of £900 [A]. TSRSim was used as an alternative to traditional design
storms across the Southern Water area to estimate floods with a return
period of 1 in 30 years. The flexibility of this tool is estimated by MWH to
have enabled savings of the order of £2 Million on a programme valued at £80
Million [B].
4.2 Land use management
Our experimental evidence on the physical links between rural land use
and floods (Wheater et al.) has fundamentally changed national attitudes
and policy. For example, we refer to the Pontbren hydrology work,
described in Section 2 (underpinning research) which was jointly run by
Imperial College and CEH Bangor (50%/50%). From the Woodland Trust Wales
report, the "Pontbren work has fundamentally changed our understanding of
the role of broadleaved trees in the farmed landscape and is now changing
policy and practice" [C]. Hence the research on trees and flooding has had
a direct influence on the Welsh Government's new land management scheme
for Wales [D] (`Glastir') and local implementations The Coed Cadw will
confirm that the next Rural Development Plan for Wales (2013-2020) is
drawing heavily on the experience and the evidence derived from Pontbren
and that it will influence the shape and focus of future agri-environment
payments to farmers [E].
The underpinning research on soil hydrology and land use has been used
directly by the Environment Agency Wales to map priority areas for
improved land management. One of the GIS water quantity layers was based
around the evidence from Pontbren and key areas in Wales have been
identified where similar activities to those within Pontbren could lead to
a reduction in flood risk in the upper Severn [D], with consequent
benefits for western England. Another example of the impact of the new
evidence and numerical model results was their use in the Foresight Future
Flooding update, which contributed to the Cabinet Office's 2008 policy
report (the "Pitt Review") recommendation that "rural land management
approaches should be considered as part of the portfolio of measures to
deal with flood risk and, where appropriate, as part of the programme to
deliver more working with natural processes" [F]. They have also been used
to guide the Office of Public Works (Ireland) in informing the Directorate
General's review of climate proofing. Our research into flood flow
modelling approaches has also had a major impact on training and education
of students and practitioners, demonstrated by sales of our books [G] and
downloads of our teaching software.
4.3 Urban pluvial flood modelling
The urban floods research has delivered models that have impacted practice
in flood studies in the UK and internationally. In 1998 we took part in the
CIRIA (Construction Industry Research and Information Association) Committee
for development of CIRIA555 Sustainable Urban Drainage Design and Best
Practice Manual, in which the term "SUDS" was coined, resulting in the
industry training module which has been used ever since. Our AOFD method and
software tool (see underpinning research section) has been independently
evaluated and recommended for practical use by the UK Water Industry
Research organisation (UKWIR). Before this model there was no appropriate
software product on the market that would enable automatic processing of
urban drainage features needed for reliable modelling of urban runoff, and
it now forms the basis of commercial software (e.g. Infoworks and TuFlow)
which are dominating UK and many international markets [H].
This tool has been used extensively by consultants for mapping surface
water flood risk in the UK (Colindale, Borough of Barnet [H]) and in
several cities in Serbia (e.g. Novi Beograd, Novi Sad, Sabac). Its
inclusion into an integrated modelling system, 3DNet-SewNet, has led to
the software being used by a significant percentage (cc 50%) of younger
and mid-career professionals in Serbia and neighbouring countries.
Similarly, the AOFD method and its principles have been incorporated into
the latest version of the main commercial software package in Germany
(Graphical Interactive Planning system — GIPS) by ITWH (Hannover) [I]. The
GIPS "has over 500 users predominantly in German speaking countries. This
is now a customer system with about €2.5M market value"[I]. Our
methodology for storm drainage master planning has had clear societal and
economic impacts: it has been adopt ed by the Brazilian consortium (
Enger, Promon, CKC) and used by the chief consultant company Hidrostudio
in development of the Master Drainage Plan for the River Tiete in Sao
Paulo, Brazil, which was then used over the last 12 years for detailed
planning of improvements to Sao Paulo's drainage. Additionally, in the
most recent project for urban flood mitigation project of the Sao Paulo's
central commercial area (Anhangabau), the AOFD model has been used for
assessment of flood risk.
Sources to corroborate the impact
[A] Technical Director, HR Wallingford to corroborate the investment of
£200,00 into the development of TSRSim by HR Wallingford Software in 2005
[B] Principal Engineer, MWH UK Ltd. To corroborate the enabled savings of
the order of £2 Million on a programme valued at £80 Million by MWH.
[C] Coed Cadw (Woodland Trust) Wales Needs More Native Trees!: An
information briefing for the Petitions Committee of the National Assembly
for Wales and associated press release.
http://www.woodlandtrust.presscentre.com/ImageLibrary/detail.aspx?MediaDetailsID=565
Also available here
[D] "Glastir Targeted Element: An Explanation of the Selection Process",
p4, Welsh Assembly Government and accompanying explanatory email from EA
Wales).
http://wales.gov.uk/topics/environmentcountryside/farmingandcountryside/farming/schemes/glastir/advanced/document/glastirteexpanselectionprocessmaps/?lang=en.
Also available here
[E] Director, Coed Cadw to confirm that the next Rural Development Plan
for Wales (2013-2020) is drawing heavily on the experience and the
evidence derived from Pontbren hydrology work.
[F] The Pitt Review — Learning Lessons from the 2007 floods — p 132,
Cabinet Office. Available at
http://webarchive.nationalarchives.gov.uk/20080906001345/http://cabinetoffice.gov.uk/thepittreview/final_report.aspx.
Also available here
[G] For example: Wagener, T., Wheater, H. and Gupta, H.V. (2004) Rainfall
Runoff Modelling in Gauged and Ungauged Catchments. Imperial College
Press, 306 pp. Sales to date >500. ISBN: 978-1-86094-466-6 (hardcover).
ISBN: 978-1-78326-066-9 (ebook)
[H] Program Delivery Manager, Golder Associates Ltd to confirm that the
model developed forms the basis of commercial software (e.g. Infoworks and
TuFlow) which are dominating UK and many international markets extensively
being used by consultants for mapping surface water flood risk in the UK
[I] CEO of the Institut für Technisch-Wissenschaftliche Hydrologie GmbH
(ITWH) confirm that the method and its principles have been incorporated
into the latest version of the main commercial software package in Germany
(Graphical Interactive Planning system — GIPS) by ITWH (Hannover)