Methodology - Response of Flood Events to Land Use and Climate Change - page 67

Table 3.4 Land cover classes and surface roughness coefficients [ 49 ]
Land cover classes Surface roughness coefficients

Coniferous forests 0.1

Broad-leaved forests 0.1

Natural grassland 0.35

Arable land/permanent crops 0.35

Pastures 0.035

Bare rocks 0.029

Black marls 0.029

Urban fabric 0.012

Airdrome 0.012

Water course 0.02-0.07

Marshes and water bodies 0.035

values were simulated to achieve the satisfactory simulation results [ 48 ]. The
Manning equation is presented as follows:
V ¼ R 2 = 3 S

p

ð 3 : 16 Þ

n

Hydraulic radius R ¼ A = P ¼ w hi w þ 2h ð Þ ð 3 : 17 Þ

In this research, based on physical characteristics of channel and floodplain areas,
the Manning's coefficient based on Chow [ 49 ] was considered as a reference.
Depending on the land use map, the values are shown in Table 3.4 .
The table represents the surface roughness values used for flood simulation. The
roughness coefficient in the channel (river bed) varied between 0.02 and 0.07 to
calibrate models based on the optimization of roughness values in the channel and
beds of the river.

3.8 Calibration Procedures

Generally, hydraulic models are calibrated by reducing the difference between
calculated and measured flow conditions. According to Visser [ 50 ], the differences
between calculated and measured flow conditions are reduced by expert judgment
with regard to the effect of various specified hydraulic roughness components on
the flow conditions, or by a recalculation of the flow conditions with adapted
hydraulic roughness values. Optimization of the model needs a clear agreement or
disagreement between the observed and modeled data [ 11 ]. Muthukishnan [ 51 ]
also defined calibration tests as a comparison between the values of simulation
with observed outputs.
One of the systematic methods was developed by Wijbenga et al. [ 52 ]. He
developed the basis of a function ministration using the simple method as proposed
by Nelder and Mead [ 53 ]. The calibration method is illustrated in Fig. 3.7 .