Environmental Engineering Reference
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physics-based models of runoff generation, the
regionalization of the metamodel parameters, and
their linkage to a fine-scale channel network
routing model. The upper limit on the scale at
which this approach can operate is typically of the
order of hundreds of square kilometres, and is
defined by the scale atwhichfloodplain inundation
starts to have a significant influence on the flood
hydrograph, Therefore, in order to assess impacts
on an urban receptor, for example, the mesoscale
catchment models would need to be linked with
the flood inundation models described elsewhere
in this topic (see Part 4, Flood Modelling and
Mitigation).
The validation of the SPR modelling approach
and the estimation of uncertainty in model
predictions is a subject of critical importance in
a decision-making context, and is the subject of
Chapter 14 by Beven. This subject has not been
discussed in any detail above, but the SPRmodel-
ling will employ state-of-the-art approaches to
the conditioning of model predictions using
observed data and the estimation of prediction
uncertainty. The information tracking approach
can be used to track uncertainty as it propagates
through the model chain, and it is therefore
intended tomap the uncertainty in the vulnerabi-
lity maps.
In an ideal world, a topic of this kind would
contain a prescription for a methodology that
would allow land use management impacts to be
assessed, and appropriate flood risk mitigation
measures to be evaluated and put in place within
the landscape as a routine procedure. Unfortunate-
ly, we are still some way from achieving this
ideal, but are making substantial progress in
constructing the key building blocks for such
a methodology. At this point in time, the follow-
ing conclusions can be drawn:
1
There is substantial evidence that modern land
use management practices have enhanced surface
runoff generation and flooding at the local scale.
2
No clear evidence has yet been found that
changes in land use management practices have
created impacts at the catchment scale. This may
be because of the overriding effects of climatic
variability, and because high-quality data that
portfolio of flood risk management measures will
need to be considered as part of any catchment
flood riskmanagement plan, in linewith theMSW
strategy, and the environmental, social and eco-
nomic dimensions of sustainabilitywill need to be
assessed for any portfolio of measures. Moreover,
the measures implemented will need to be adap-
tive and resilient under climate change pressures.
A strategic approach to the analysis and model-
ling of change necessitates the adoption of a broad
holistic modelling framework that encompasses
the climatic and social drivers, the prediction of
impacts and the integrated assessment of response
measures based on economic, social and environ-
mental criteria. The DPSIR framework for the
analysis of change has been integrated with
the Source-Pathway-Receptor (SPR) modelling of
impacts and responses to provide a strategic ap-
proach that can support sustainable flood risk
management. In implementing such an approach,
the major challenges are to integrate all of the
technical elements into the SPR modelling
approach, and then to incorporate the SPR model-
ling into an integrated sustainability assessment.
The latter will involve confronting the formidable
challenge of integrating the technical and social
aspects of flood risk management that have here-
tofore tended to be researched within separate
disciplinary domains, but which are encompassed
by FRMRC research.
This chapter has focused on the technical sub-
ject of how land use management interventions
can impact runoff generationat source and possibly
downstream flooding within a catchment, and has
considered how any adverse impacts might be
mitigated. Catchment-scale modelling of the rain-
fall runoff process is at the core of the SPR model-
ling, with the source being at the scale of the
farmer's field, the pathwaybeing the drainage/river
channel network, and the receptor being the point
of downstream impact. Current rainfall-runoff
models are not fit for purpose in this regard, and
new concepts such as information tracking and
adjoint modelling are being developed as key ele-
ments of SPR modelling and the construction of
vulnerability maps. The SPR modelling approach
links local-scalemetamodels that emulate detailed
