Article Highlights
• GIS-based analysis identified flood hazard, vulnerability
and risk zones in the Shebelle River Basin, Somalia.
• Majority of the basin falls in very low to moderate risk
ranges, with small areas at high and very high risk.
• Flood hazard, vulnerability and risk maps can guide flood protection efforts and raise awareness among
local populations
Article Highlights
• GIS-based analysis identified flood hazard, vulnerability
and risk zones in the Shebelle River Basin, Somalia.
• Majority of the basin falls in very low to moderate risk
ranges, with small areas at high and very high risk.
• Flood hazard, vulnerability and risk maps can guide
f
lood protection efforts and raise awareness among
local populations.
Flood risk management relies heavily on predict
ing the size of river floods. There are three common
approaches to flood prediction: (i) monitoring storm
progress (e.g., quantity of rainfall) can be used to fore
cast short-term flood events; (ii) assessing the frequency
of flooding through statistical analyses allows determin
ing the recurrence interval for any year and for a given
discharge in the stream (without explicitly characteriz
ing the flood area); and (iii) evaluating the frequency of
flooding through statistical analyses allows determining
the recurrence interval for any year and for a given dis
charge in the stream without explicitly
Flood inventory map
The preparation of a flood inventory map is necessary for
the accurate assessment of flood susceptibility zonation.
The flood inventory map of the study area was generated
Fig. 1 Geographical location
for Shebelle River Basin in
Somalia a Somalia and b Part
of Shebelle River Basin
from FAO website
Data acquiring and preparation of thematic
maps
Defining a clear and efficient methodology is vital for the
quality of the findings of the study. The various input data
were required to achieve the aim of this research and to
have accurate results, Table 1 shows data used and their
sources. In this study, secondary research data sources
were used and collected
Flood hazard parameters (FHP)
The extent of flooding is influenced by a variety of factors
including the physical features of the topography, rain
fall, geology, drainage systems and soil texture. Through
literature review and field investigation, we have consid
ered only 7 most important parameters that contribute
to flooding.
Fig. 2 Methodological flow
chart of the study
2.4.1.1 Elevation Lowland locations are more vulnerable
to flooding as water moves from higher to lower eleva
tions [33]. The elevation map is made possible by reclas
sifying the DEM. The Shebelle River catchment’s topo
graphic elevation ranges from 3 to 2821 m. The upstream
elevation is extremely high, whereas the downstream
level is extremely low. As a result of the high elevation and
steep slope upstream, there is considerable runoff after
heavy rains, causing high floods downstream. As a result,
the land slope is flat, and the river course allows overflow.
A Digital Elevation Model (DEM) specifies the eleva
tion of any point in a particular area at a specific spatial
Flood hazard mappin
Analysing of flood influencing factors
for creating flood vulnerability mapping
Flood vulnerability mapping
Flood risk mapping
The final result of the present study is the flood risk zona
tion (FRZ) map, which is a combination of the flood haz
ard zone (FHZ) map and the flood vulnerability zone (FVZ)
map. The risk of flooding is depicted on a map that shows
five levels of risk, ranging from very low to very high
(Fig. 7c). The final flood risk map created using the AHP
GIS technique comprised 5.7% and 12.13% areas classified
as very high and high flood risk, 23.65% areas classified as
medium flood risk, and 30.88% and 27.64% areas classified
as low and very low flood risk. Most of the high and very
high flood risk zone falls in the coastal areas, especially in
Jilib, Baraawe, Marka and Wanlaweyne districts.
3.6 Validation of the model
The study quantitatively verified the AHP output with the
flood inventory map through ROC-AUC. The ROC-AUC
has been performed by comparing the FHZ map with 59
f
lood points employing the ‘ArcSDM’ tool in the ArcGIS
software.
Conclusions
The objective of this study was to prepare flood hazard, vul
nerability, and risk maps in a specific part of the Shebelle
River Basin of Somalia by analyzing flood-triggering factors
using the GIS-based AHP technique. By using Arc GIS soft
ware, the following flood-generating parameters were cre
ated during the development of flood hazard, vulnerability
and risk map; Elevation, Slope, Soil, Geology, Distance to
river, Rainfall, Drainage density, Land use/Land cover, Popu
lation density, Distance to road, GMIS and HBASE maps.
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- Received: 4 January 2023 / Accepted: 4 April 2023
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