Methodology - Response of Flood Events to Land Use and Climate Change - page 79

In terms of bed velocity, shear stress can be expressed as:

s 0 ¼ c ð Vn Þ 3 = 2 S 1 = 4

ð 3 : 33 Þ

where,
V = bed velocity; n = Manning's coefficient.

3.10 Scenarios

In order to have valuable and basic information available for any future man-
agement, it is necessary to provide the authorities, stockholders, other scientists,
and the public with flood hazard maps which are basic but which contain funda-
mental information for any environmental, technical, economical, and political
decisions regarding flood event management. This shows the potential adverse
consequences associated with different flood scenarios for civil protection pur-
poses, including information on potential sources of environmental damages as a
consequence of floods [ 70 ].

3.10.1 DEM Scenario

Topography is considered an important land surface characteristic that affects the
flow distribution over the channel and floodplain in the catchment. According to
Vaze [ 1 ] and other investigators, such as Abbott et al. [ 71 ] and Rohdenburg et al.
[ 72 ] all of spatially distributed hydraulic and hydrological models use topography
as a DEM to derive bathymetry (Channel). Alkema [ 73 ] also mentioned that in
hydraulic modeling, the output is affected largely by model input parameters, such
as the DEMs and other topography related properties such as slope gradients, slope
aspects, and drainage density.
In flood modeling, it is a great interest to know how much the resolution of
DEM determines and affects on the model outputs. Researchers have also realized
that DEM quality and resolution significantly affect the accuracy of any extracted
hydrological features and drainage networks delineation [ 74 ].
The indirect effects of DEM on hydrodynamic simulation's results can be seen
on the model inputs, such as the hydraulic roughness, which are simulated at the
scale of the DEM elements. Hydraulic roughness can change with DEM resolution
and, as such, also affect simulation results.
Almost all of the applications including water resource management and
hydrological modeling required a high quality of DEMs because the accuracy of
DEMs does affect the accuracy of hydrological predictions. There are numerous
studies [ 47 , 75 - 77 ] reported in the literature which compared spatial indices
derived from different resolution DEMs (e.g., 100 and 10 m grid cell resolution).