Authors :
Anil Pangeni; Umesh Bhurtyal; Madan Pokhrel; Samrat Poudel; Netra Bahadur Katuwal
Volume/Issue :
Volume 8 - 2023, Issue 12 - December
Google Scholar :
http://tinyurl.com/bdh6fhdx
Scribd :
http://tinyurl.com/yxbn478m
DOI :
https://doi.org/10.5281/zenodo.10389870
Abstract :
Floods, earthquakes, forest fires, landslides,
and other natural hazard are common in Nepal. Among
them, the flood is one of the natural disasters and that
occurred in the Narayani River basin. The Narayani
River Basin's exposures and vulnerabilities are at
danger from a flood catastrophe of this kind, hence this
studies attempts to reduce and control the risk of
flooding in order to better manage disasters. The factors
of flood hazard, flood exposures, and flood vulnerability
are investigated as part of the ward-level flood risk
assessment, which aims to prevent and manage the flood
disaster. The hydraulic model (HEC-RAS) for the 2018
flood event was used in this study to create the GIS-
based modeling of the flood inundation maps.
Additionally, it calculated the various return periods for
floods in the river basin—5, 10, 25, 50, 75, and 100
years. Furthermore, the flood extent was confirmed
using the flood map produced by the Google Earth
Engine (GEE) using remotely sensed techniques. For
Hydraulic modelling, ALOS/PALSAR Digital Elevation
Model (12.5m.) spatial resolution was used. In addition,
RAS-MAPPER generated the geometric data for the
hydraulic modeling, which was then transferred into
HEC-RAS. This data included the cross-section, flow
route, streamline, and bank lines. On both sides of the
river, the necessary Manning value "n" values were
computed for every cross-section. The steady-flow
models of the anticipated flood hydrographs were
created using the hydraulic model. Google Earth Engine
(GEE) flood maps generated from Sentinel-1C radar
satellite data were used to validate the results for the
2018 flood events. When comparing the simulated
result's flood inundation area with the remote sensing
data's flood area, the overlap area for the 2018 flood
event is 65%. Additionally, the flood area is verified. In
addition, the hydraulic model generated flow conditions
for 5, 10, 25, 50, 75, and 100 year return periods. The
river basin's surface water level and flood extent are
both progressively rising. In order to effectively manage
and prepare for potential flood hazards in the study
area, an analysis of the flood risk assessment was
conducted by taking into consideration three primary
factors: the flood hazard map, flood exposure, and flood
vulnerability. The layers of the population, crops,
schools, hospitals, and road network were all exposed to
flooding, and the factors that determined flood
vulnerabilities were literacy, urban area, and agecomposition (less than 14 and more than 65). The higher
flood risk area was found in Ward number 1, 3,
4,16,18,26 of Bharatpur metropolitan, Gaindakot
municipality ward number 1 and 12, 15 of
Madhyabindu Municipality.
Keywords :
Hydraulic model, Flood inundation, Flood risk, Flood exposure, Flood vulnerability, Flood hazard.
Floods, earthquakes, forest fires, landslides,
and other natural hazard are common in Nepal. Among
them, the flood is one of the natural disasters and that
occurred in the Narayani River basin. The Narayani
River Basin's exposures and vulnerabilities are at
danger from a flood catastrophe of this kind, hence this
studies attempts to reduce and control the risk of
flooding in order to better manage disasters. The factors
of flood hazard, flood exposures, and flood vulnerability
are investigated as part of the ward-level flood risk
assessment, which aims to prevent and manage the flood
disaster. The hydraulic model (HEC-RAS) for the 2018
flood event was used in this study to create the GIS-
based modeling of the flood inundation maps.
Additionally, it calculated the various return periods for
floods in the river basin—5, 10, 25, 50, 75, and 100
years. Furthermore, the flood extent was confirmed
using the flood map produced by the Google Earth
Engine (GEE) using remotely sensed techniques. For
Hydraulic modelling, ALOS/PALSAR Digital Elevation
Model (12.5m.) spatial resolution was used. In addition,
RAS-MAPPER generated the geometric data for the
hydraulic modeling, which was then transferred into
HEC-RAS. This data included the cross-section, flow
route, streamline, and bank lines. On both sides of the
river, the necessary Manning value "n" values were
computed for every cross-section. The steady-flow
models of the anticipated flood hydrographs were
created using the hydraulic model. Google Earth Engine
(GEE) flood maps generated from Sentinel-1C radar
satellite data were used to validate the results for the
2018 flood events. When comparing the simulated
result's flood inundation area with the remote sensing
data's flood area, the overlap area for the 2018 flood
event is 65%. Additionally, the flood area is verified. In
addition, the hydraulic model generated flow conditions
for 5, 10, 25, 50, 75, and 100 year return periods. The
river basin's surface water level and flood extent are
both progressively rising. In order to effectively manage
and prepare for potential flood hazards in the study
area, an analysis of the flood risk assessment was
conducted by taking into consideration three primary
factors: the flood hazard map, flood exposure, and flood
vulnerability. The layers of the population, crops,
schools, hospitals, and road network were all exposed to
flooding, and the factors that determined flood
vulnerabilities were literacy, urban area, and agecomposition (less than 14 and more than 65). The higher
flood risk area was found in Ward number 1, 3,
4,16,18,26 of Bharatpur metropolitan, Gaindakot
municipality ward number 1 and 12, 15 of
Madhyabindu Municipality.
Keywords :
Hydraulic model, Flood inundation, Flood risk, Flood exposure, Flood vulnerability, Flood hazard.
