Flood Hazard Mapping and Vulnerability Analysis …
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is considered low hazard, 1–3 m is considered moderate, and greater than 3 m is
considered as high hazard class.
It is assumed that lesser flood depth has less effect on the people and properties,
and higher ones have larger effect. The flood hazard map for 50 years return period
is shown in Fig. 3a.
To prepare flood vulnerability maps, landuse map was used. The landuse map of
the study area is clipped by the flood depth boundary polygon to prepare the flood
vulnerability maps. The flood vulnerability map for 50 years return period is shown
in Fig. 3b.
4 Results
The performance of the one-dimensional steady hydrodynamic model was evaluated by comparing the flood depth observed at the Seti–Phoolbari hydrological
station with the simulated depth. The statistical parameters used for the model performance evaluation were coefficient of determination R
2 ) and Nash–Sutcliffe efficiency
(NSE), and their values were found to be 0.951 and 0.819, respectively.
The flood hazard and vulnerability analyses along with exposed people and
buildings are summarized in terms of affected area in Tables 1 and 2.
5 Conclusions and Recommendations
This study was done to prepare hazard and vulnerability map and exposure information using HECRAS for one-dimensional steady hydrodynamic modeling, Arc GIS
as the interface for spatial data analysis and processing and HEC-GeoRAS to link
Arc GIS and HECRAS. The values of R
2 and NSE show that the performance of the
model can be rated as very good [9].
The result shows that the area, population, and buildings affected by the floods in 2,
5, 10, 50, and 100 years return periods for Pokhara Metropolitan City are increasing.
The assessment of flood hazard shows that the flood intensity increases as lower
flood depth decreases and higher flood depth area increases. The hazard map for
50 years return period shows that specific areas along the Seti River like Shri siddhi
box gadh, Pokhara Rangashala, Manipal College, Ramghat area, Kaskeri Chautari,
and some part of Prithvi and Pokhara Baglung Highway as well as many street roads
are at high risk. Hence, river training works are recommended for those high risk
areas. The result of flood vulnerability further shows that the most vulnerable area
is agricultural area for all return periods which might have direct impact on the food
security for the area.
Landcover of 2010 was used in this study, and on the contrary, recent landcover
could represent the present scenario more reliably. Though 12.5 m resolution DEM
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is considered low hazard, 1–3 m is considered moderate, and greater than 3 m is
considered as high hazard class.
It is assumed that lesser flood depth has less effect on the people and properties,
and higher ones have larger effect. The flood hazard map for 50 years return period
is shown in Fig. 3a.
To prepare flood vulnerability maps, landuse map was used. The landuse map of
the study area is clipped by the flood depth boundary polygon to prepare the flood
vulnerability maps. The flood vulnerability map for 50 years return period is shown
in Fig. 3b.
4 Results
The performance of the one-dimensional steady hydrodynamic model was evaluated by comparing the flood depth observed at the Seti–Phoolbari hydrological
station with the simulated depth. The statistical parameters used for the model performance evaluation were coefficient of determination R
2 ) and Nash–Sutcliffe efficiency
(NSE), and their values were found to be 0.951 and 0.819, respectively.
The flood hazard and vulnerability analyses along with exposed people and
buildings are summarized in terms of affected area in Tables 1 and 2.
5 Conclusions and Recommendations
This study was done to prepare hazard and vulnerability map and exposure information using HECRAS for one-dimensional steady hydrodynamic modeling, Arc GIS
as the interface for spatial data analysis and processing and HEC-GeoRAS to link
Arc GIS and HECRAS. The values of R
2 and NSE show that the performance of the
model can be rated as very good [9].
The result shows that the area, population, and buildings affected by the floods in 2,
5, 10, 50, and 100 years return periods for Pokhara Metropolitan City are increasing.
The assessment of flood hazard shows that the flood intensity increases as lower
flood depth decreases and higher flood depth area increases. The hazard map for
50 years return period shows that specific areas along the Seti River like Shri siddhi
box gadh, Pokhara Rangashala, Manipal College, Ramghat area, Kaskeri Chautari,
and some part of Prithvi and Pokhara Baglung Highway as well as many street roads
are at high risk. Hence, river training works are recommended for those high risk
areas. The result of flood vulnerability further shows that the most vulnerable area
is agricultural area for all return periods which might have direct impact on the food
security for the area.
Landcover of 2010 was used in this study, and on the contrary, recent landcover
could represent the present scenario more reliably. Though 12.5 m resolution DEM