Environmental Engineering Reference
In-Depth Information
Flood Inundation Modelling
to Support Flood Risk Management
12
GARETH PENDER AND SYLVAIN N
´
ELZ
Introduction: the Role of Modelling in
Flood Risk Management
ques are considered outside the scope of the cur-
rent text, as at the present time their application is
generally limited to the simulation of local fea-
tures within the pathway.
The outcome of the models discussed here is an
estimate of the impact of flooding upon receptors
(Fig. 12.1). In this respect, predictions of inunda-
tion extent, depth and velocity coupled to wave
celerity are all essential outputs from the models.
This chapter deals exclusively with the techni-
cal aspects of model development and implemen-
tation, with examples of model application being
left until later chapter.
Recent major flood events in Europe and else-
where (see Chapter 1) linked to growing concerns
of the impact of climate change on flood magni-
tude and frequency have resulted in many govern-
ments adopting policies of flood riskmanagement.
As discussed previously, this requires a dynamic
assessment of risk accounting for both spatial and
temporal changes to the flooding system. Such an
assessment is not possible without the adoption
of a framework within which the various drivers
and pressures for change can be systematically
evaluated. One such framework, Drivers, Pres-
sures, States, Impacts, Responses (DPSIR), as sug-
gested by Wheater et al.
Modelling Methods
(2007), is shown in
Figure 12.1.
The techniques discussed in this chapter relate
to the 'Modelling of state' (see box highlighted
blue in Fig. 12.1) within this framework. In par-
ticular this chapter relates to predicting the per-
formance of 'pathways' within the flood system.
Pathways are essentially conveyance routes for
flood water and may include rivers, estuaries,
coasts, pipes and floodplains. The chapter reviews
a subset of modelling methodologies available
ranging fromone-dimensional (1D)methods based
on the St-Venant equations through to two-
dimensional (2D) methods utilizing the shallow-
water equations. Three-dimensional (3D) techni-
Overview
Flood modelling methods currently in use in flood
risk management applications can be divided into
a number of approaches, presented in Table 12.1,
characterized by their dimensional representation
of the flood modelling process, or the way they
combine approaches of different dimensions. Ap-
plications necessary to support the implementa-
tion of flood riskmanagement strategies in theUK
aremainly covered by the approaches referred to in
Table 12.1 as 1D, 1D
þ
, 2D- and 2D methodolo-
gies. These are therefore of greatest interest in the
present chapter. 3D methods derived from the 3D
Reynolds averaged Navier-Stokes equations can
be used to predict water levels and 3D velocity
fields in river channels and floodplains. However,
significant practical challenges remain to be over-
come before such models can be routinely applied
