Environmental Engineering Reference
In-Depth Information
run times. The objective is to provide reliable
evidence to assist decision-making in areas such
as issuing of warnings or operation of barriers.
Use of a detailed model to achieve an accuracy of
25mm but requiring 1 hour to run is not appro-
priate if a simpler model can achieve 100mm
accuracy in a 1-minute simulation. A range of
models are provided for flood forecasting in the
Thames Estuary so that simple and quick models
can be run rapidly first, and then more complex
(and slower) models can be run later to provide
refined results (Fig. 23.6). For example, simple
pseudo-2D flood cell models can be run initially
to assist in immediate decision-making, followed
by the slower 2D TUFLOW models to provide
refined outputs.
included in the simulation, and 'what if' scenarios
undertaken to help optimize operational deci-
sions. Simulation results are automatically pro-
cessed to generate tabulated maximum water
levels, time series plots of water levels and flood
extentmaps, which can all be viewed inThemis or
exported to other systems. The software is popu-
lated with 2D models covering the 23 Thames
Region embayments, 1D flood cell models provid-
ing simplified but quick-running models of the 23
Thames Region embayments and 12 Anglian and
Southern Region embayments, and the 1D Tidal
Thames model. The 2D and 1D flood cell models
are dynamically linked to the 1D model. Further
details of the system are provided in Tarrant
et al. (2005), with further information on the
selection of models provided inWicks et al. (2004).
TE2100: Strategic Flood Risk Management
Appropriateness of modelling methods
Introduction
For forecasting, the run times and robustness of
models are of crucial importance, and lower accu-
racymaywell be acceptable in order to achieve fast
The Environment Agency's Thames Estuary 2100
project (TE2100) was set up to develop a plan for
Trigger event
Extreme event orbreach
Details fed into NFFS/Themis
Model simulations
Inform operational decision
(e.g. issue warning)
Request more
detailed results
Provide refined
model results
Initiate local emergency
response plan
Establish emergency
control
Fig. 23.6
Modelling to support operation decision-making.
