Environmental Engineering Reference
In-Depth Information
Setting the Scene for
Flood Risk Management
JIM W. HALL AND EDMUND C. PENNING-ROWSELL
The Changing Context of Modern Flood
Risk Management
optimization of the costs and benefits of flood
defence was laid out in van Dantzig's (1956) sem-
inal analysis.
However, modern flood risk management no
longer relies solely upon engineered flood defence
structures, such as dikes, channel improvement
works and barriers. It also considers a host of other
measures that may be used to reduce the severity
of flooding (e.g. land use changes in upstream
catchments) or reduce the consequence of flooding
when it does occur, by reducing either exposure
(White and Richards 2007; Richards 2008) or vul-
nerability (Tapsell 2002). The criteria for the as-
sessment of flood risk management options are
now seldom solely economic (Penning-Rowsell
et al. 2005; Johnson 2007a), but involve considera-
tions of public safety (Jonkman and Penning-
Rowsell 2008), equity (Johnson 2007b) and the
environment (Green 2004). Furthermore, an in-
creasing recognition of non-stationarity (Milly
et al. 2008) means that flood risk management
involves explicit consideration of the ways in
which flood risk may change in future, due, for
example, to climate change or the apparently
inexorable process of floodplain development
(Parker and Penning-Rowsell 2005). This leads to
the notion of flood risk management being a con-
tinuous process of adaptive management rather
than a 'one-off' activity (Hall et al. 2003c; Hutter
and Schanze 2008).
The locus of power is also changing in many
countries as governments seek more effective and
efficient institutional arrangements. In the UK,
as well as the devolved administrations in Wales
and Scotland now taking somewhat different
Amajor shift in approaches to the management of
flooding is now underway in many countries
worldwide. This shift has been stimulated by se-
vere floods, for example on the Oder (Odra; 1997),
Yangtze (1998), Elbe (Labe; 2002), Rh ˆ ne (2003), in
New Orleans (2005), on the Danube (2006) and in
the UK (2000, 2007 and 2009). Also important has
been a recognition of the relentless upward global
trend in vulnerability to flooding and hence losses
(Munich Re Group 2007), as well as threats from
the potential impacts of climate change on flood
frequency. In this context this chapter examines
the main characteristics of the emerging approach
to flood riskmanagement, as a prelude to themore
detailed exploration of methods and models that
follows in this volume.
Whilst recent floods have been a stimulus for
changing flood risk management policy and prac-
tice in the UK (Johnson 2005; Penning-Rowsell
2006), the notion of an integrated risk-based ap-
proach to flood management is in fact well estab-
lished (National Academy of Engineering 2000;
National Research Council 2000; Sayers et al.
2002; Hall et al. 2003c). Methods for probabilistic
risk analysis have been used for some years in the
narrower context of flood defence engineering
(CUR/TAW 1990; Vrijling 1993; USACE 1996;
Goldman 1997). Indeed the notion of risk-based
