Urban flood impact assessment: A state-of-the-art review

TLDR: A state-of-the-art literature review on flood impact assessment in urban areas, detailing their application, and their limitations is presented in this article, which describes both techniques for dealing with individual categories of impacts, as well as methodologies for integrating them.

Abstract: Flooding can cause major disruptions in cities, and lead to significant impacts on people, the economy and on the environment. These impacts may be exacerbated by climate and socio-economic changes. Resilience thinking has become an important way for city planners and decision makers to manage flood risks.Despite different definitions of resilience, a consistent theme is that flood resilient cities are impacted less by extreme flood events. Therefore, flood risk professionals and planners need to understand flood impacts to build flood resilient cities. This paper presents a state-of-the-art literature review on flood impact assessment in urban areas, detailing their application, and their limitations. It describes both techniques for dealing with individual categories of impacts, as well as methodologies for integrating them. The paper will also identify future avenues for progress in improving the techniques.

Figures

Figure 5 - General approach for the estimation of loss of life due to flooding (from Jonkman et al. (2008b))

Figure 3 - Flood map of central Dhaka with building classifications

Figure 2 - Main steps in flood impact assessment

Figure 1 - Typical depth-damage functions (adapted from UK Multicoloured Manual (Penning-Rowsell et al. 2005))

Figure 4 - Damage per unit building for Central Dhaka

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ORE Open Research Exeter
TITLE
Urban flood impact assessment: A state-of-the-art review
AUTHORS
Hammond, Michael J.; Chen, Albert S.; Djordjevic, Slobodan; et al.
JOURNAL
Urban Water Journal
DEPOSITED IN ORE
28 November 2013
This version available at
http://hdl.handle.net/10871/14066
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publication

Urban flood impact assessment: A state-of-the-art review
M. J. Hammond
1
, A. S. Chen
1
, S. Djordjević
1
, D. Butler
1
, O. Mark
2
1
Centre for Water Systems, University of Exeter, Exeter, UK
2
DHI Group, Hørsholm, Denmark
Email: m.j.hammond@exeter.ac.uk

Urban flood impact assessment: A state-of-the-art review
Flooding can cause major disruptions in cities, and lead to significant impacts on
people, the economy and on the environment. These impacts may be exacerbated
by climate and socio-economic changes. Resilience thinking has become an
important way for city planners and decision makers to manage flood risks.
Despite different definitions of resilience, a consistent theme is that flood
resilient cities are impacted less by extreme flood events. Therefore, flood risk
professionals and planners need to understand flood impacts to build flood
resilient cities. This paper presents a state-of-the-art literature review on flood
impact assessment in urban areas, detailing their application, and their
limitations. It describes both techniques for dealing with individual categories of
impacts, as well as methodologies for integrating them. The paper will also
identify future avenues for progress in improving the techniques.
Keywords: Urban flooding; Resilience; Impact assessment; ; Urban water
management.

Introduction
Cities are social hubs, and life in cities is reliant on a number of services and functions
such as energy and water provision, transport links, housing, education and
employment. Urban flooding can cause significant disruption to these services, and
wider impacts on the population. There have been many recent notable examples,
including flooding in Brisbane in January 2011, widespread flooding in Thailand that
inundated Bangkok during the 2011 monsoon season, and flash flooding caused by
extreme rainfall in Beijing in July 2012.
A number of trends suggest that the problem of urban flooding is likely to
increase. The first of these is the growing number of people that live in cities; the
world’s population is becoming increasingly urban. The United Nations (UN) recently
reported that the world’s population living in urban areas has overtaken the rural
population, and it is projected that the world’s urban population will grow both in
absolute terms, and as a fraction of a growing global population (United Nations
Department of Economic and Social Affairs/Population Division 2012). Between 2011
and 2050, the world population is projected to increase by 2.3 billion, from 7.0 billion to
9.3 billion. At the same time, the population living in urban areas is projected to
increase from 3.6 billion in 2011, to 6.3 billion in 2050. This represents a growth from
51% to 68% of the global population. As more people move to the cities they inevitably
turn green areas into impervious areas, increasing urban runoff, and as more people live
in densely populated urban areas, often situated on flood plains and low-lying coastal
areas, their exposure to flood hazards is increased.
The second trend arises from the possibility for climate change to lead to more
extreme rainfall. Some studies have already shown statistically significant trends in

extreme rainfall in the past century in Denmark (Arnbjerg-Nielsen 2006), and in North
America (Peterson et al. 2008). However, these trends are variable both across temporal
and spatial scales. As for future projections, a Special Report of the Intergovernmental
Panel on Climate Change reports that “it is likely that the frequency of heavy
precipitation … will increase in the 21st century over many areas on the globe”,
although recent analyses have “highlight[ed] fairly large uncertainties and model
biases” (Field et al. 2012).
If cities are to become more resilient to flooding, innovative and adaptable
strategies and measures are needed. Although there are many different concepts of
resilience, most authors are in agreement that a flood resilient city will have low flood
consequences if and when flooding occurs. Therefore, to build flood resilience, planners
need to understand the impacts of flooding. In the short term, these can include the risk
to life, property damage, and failure of infrastructure such as transport and electricity
networks. In the short to medium term, contaminated flood waters increase the risk of
the spread of diseases such as diarrhoea, and stagnant water provide breeding grounds
for mosquitoes, which can increase the risk of malaria and dengue fever. In the longer
term, the disruption caused by flooding can have economic consequences that extend
beyond the immediately affected region. For example, Thailand’s Gross Domestic
Product grew by only 0.1% in 2011 (following the severe flood disaster), compared to
7.8% in 2010, and 6.5% in 2012 (GDP fell in the 4
th
quarter of 2011 by an annualised
rate of 9.0%) (Office of the National Economic and Social Development Board 2012).
This article presents a state-of-the-art literature review on flood impact
assessment, focusing specifically on urban flooding. Urban flooding can include pluvial,
fluvial, groundwater and coastal flooding. Pluvial flooding results from urban drainage
that is in adequate with respect to the rainfall in an urban area. Fluvial flooding results

Frequently asked questions

Q1. What have the authors contributed in "Urban flood impact assessment: a state-of-the-art review" ?

In this paper, the authors present a literature review on flood impact assessment, focusing specifically on urban flooding, including pluvial, fluvial, groundwater and coastal flooding. 

Q2. Why do some researchers question their value for small-scale flood impact assessment studies?

In the case of developing and applying complex models such as Input-output or Computable General Equilibrium models, some researchers question their value for small-scale flood impact assessment studies, in part due to the scale of the models, and also due to the skill needed to implement them (Green et al. 2011). 

Q3. What is the role of flood impact assessment in urban areas?

In the European Funded Collaborative Research on Flood Resilience in Urban Areas (CORFU), flood impact assessments have an important role in studies that aim to improve urban flood resilience (Djordjević et al. 2011). 

Q4. Why is the monetisation of health impacts difficult and controversial?

The monetising of health impacts is difficult and controversial and likely to remain so because of the need to attach a value to human life. 

Q5. What are the two methods of assessing the health impacts of flooding?

Beyond quantifying the intangible impacts in terms of the number of peopleaffected (e.g. number of deaths, injuries, disease cases), two methods have been developed to quantify health impacts. 

Q6. What are the main types of infrastructures that are affected by flooding?

These infrastructures include telecommunications, transport services,power, emergency services, water, agriculture and food, and health care, among others (Conrad et al. 2006). 

Q7. What are the main conclusions that can be drawn from this review?

By considering expecteddamages over longer time-frames, it is possible to estimate the cost-effectiveness of different adaptation measures (Zhou et al. 2012, 2013)There are a number of conclusions that can be drawn from this review. 

Q8. What does Van der Veen (2003) define as indirect losses?

Van der Veen (2003) maintained this definition, but distinguishes between primary and secondary indirect losses, and defines primary indirect losses as business interruption costs that relate specifically to flooded businesses, whereas secondary indirect losses refer to multipliers in the economy. 

Q9. What was used to estimate the risks of infection from drinking contaminated groundwater?

Their concentrations were simulated with a hydraulic model, and a dose-response model was used to estimate the risks from drinking contaminated groundwater.