Methodology - Response of Flood Events to Land Use and Climate Change - page 76

b a

d

e

c

g

f.

Fig. 3.12 Schematization of 2D network with history stations; a upstream boundary condition
(1D), b downstream boundary condition (1D), c downstream boundary condition (2D), d history
stations, e cross sections, f line measurement, g nodes

boundary conditions should be defined in 2D schematization. The flow boundary
conditions will be connected using a flow connection node in order to define the
1D component. Figure 3.12 shows the schematization environment in SOBEK. To
determine the exact value of parameters, such as depth of water in time on specific
locations in 2D grids, the history stations nodes were defined.

3.9.5 Data Requirements, Processing, and Preparation: Setting Up
the Models

For applying the distributed hydrologic model for any purpose, it is necessary to
prepare a huge amount of spatial and temporal input data. The importance of
various input data varies according to the application of the specific purpose. For
example, in flood inundation simulations, topography layer is one of the most
important spatial input data which deals with the flow behaviour in overland flow
and floodplain areas. In any application of a hydrodynamic model, the drainage
network is delineated from the topography data or a DEM.
As the drainage network is the most critical item in surface flood simulation, it
is important that it is delineated with more reliability and accuracy. Ubaye River
was constructed in SOBEK (1D-2D) and HEC-RAS (1D) using the following
information/data:
DEM: It covers channel and floodplain areas of approximately 14 by 10 km,
with a 5 m resolution. The DEM is the digital representation of natural topo-
graphic as well as man-made features located on the surface of the earth [ 1 ] which
affects the flow of water, such as dykes, embankments, and buildings. Many of
these features have to be extracted from topographic maps, building footprint
maps, field surveys, bathymetry data, and other sources [ 3 ]. Due to lack of high
resolution of DEM across the Barcelonnette area, man-made features are added to
the DEM to create the final digital elevation surface map to use in hydrodynamic
simulation.