scholarly journals Flood Vulnerability Assessment on Selected Communities in Ikwerre Local Government Area of Rivers State, Nigeria, Using Remote Sensing and GIS Techniques

2021 ◽  
pp. 46-57
Author(s):  
E. Wali ◽  
P. O. Phil-Eze ◽  
C. H. Wizor ◽  
M. Abdullahi ◽  
O. O. Afolabi ◽  
...  
Keyword(s):  
High Risk ◽  
Water Channel ◽  
Flood Vulnerability ◽  
Risk Zone ◽  
Location Data ◽  
Vulnerable Communities ◽  
Digital Elevation ◽  
Elevation Model ◽  
Rivers State ◽  
Flood Vulnerability Assessment

A flood is an overflow of water that submerges land that is usually dry. Flooding may occur as an overflow of water from water bodies, such as river, lake or ocean, in which the water overtops or breaks levees, resulting in some of that water escaping its usual boundaries, or it may occur due to an accumulation of rain water on saturated ground in an area. To find out the most vulnerable communities, the Digital Elevation Model (DEM) and location data of selected communities were used. The Image Re-class and Map Overlay were performed on QGIS software to identify communities that are most affected. The result shows that the region has no river channel that discharge excess water easily. It also shows that four, out of twelve settlements were located at the high risk zone. The settlements are Uniport, Omuoda, Omuahunwo and Okparagwa. It was recommended that the high risk zone in the area should be provided with artificial water channel that will contain and convey surface sun-off to a nearby stream. The local authority should relocate the affected settlements to a safer zone.

scholarly journals Flood vulnerability assessment in the Accra Metropolis, southeastern Ghana

2021 ◽  
Vol 11 (7) ◽  
Author(s):  
Benjamin Wullobayi Dekongmen ◽  
Amos Tiereyangn Kabo-bah ◽  
Martin Kyereh Domfeh ◽  
Emmanuel Daanoba Sunkari ◽  
Yihun Taddele Dile ◽  
...  
Keyword(s):  
Drainage Density ◽  
Geological Structures ◽  
Flood Vulnerability ◽  
Rock Types ◽  
Digital Elevation ◽  
Annual Population ◽  
Density Values ◽  
High Runoff ◽  
Elevation Model ◽  
Very High

AbstractFloods in Ghana have become a perennial challenge in the major cities and communities located in low-lying areas. Therefore, cities and communities located in these areas have been classified as potential or natural flood-prone zones. In this study, the Digital Elevation Model (DEM) of the Accra Metropolis was used to assess the drainage density and elevation patterns of the area. The annual population estimation data and flood damages were assessed to understand the damages and population trend. This research focused primarily on the elevation patterns, slope patterns, and drainage density of the Accra Metropolis. Very high drainage density values, which range between 149 and 1117 m/m2, showed very high runoff converging areas. High drainage density was also found to be in the range of 1117–1702 m/m2, which defined the area as a high runoff converging point. The medium and low converging points of runoff were also found to be ranging between 1702–2563 m/m2 and 2563–4070 m/m2, respectively. About 32% of the study area is covered by natural flood-prone zones, whereas flood-prone zones also covered 33% and frequent flood zones represent 25%. Areas in the Accra Metropolis that fall in the Accraian and Togo series rock types experience high floods. However, the lineament networks (geological structures) that dominate the Dahomeyan series imply that the geological structures in the Dahomeyan series also channel the runoffs into the low-lying areas, thereby contributing to the perennial flooding in the Accra Metropolis.

scholarly journals GIS Based Analysis of Niger-Benue River Flood Risk and Vulnerability of Communities in Kogi State, Nigeria

2021 ◽  
Vol 2 (5) ◽  
pp. 47-56
Author(s):  
Chukwunonso Emmanuel Ozim ◽  
Oladeinde Stephen Olufemi ◽  
Abraham Salamatu Ekpo ◽  
Nnaemeka Kosiso Alamaeze ◽  
Michael Udochukwu Mbanaso
Keyword(s):  
Flood Risk ◽  
Spatial Location ◽  
Shuttle Radar Topography Mission ◽  
The State ◽  
Flood Vulnerability ◽  
Vulnerable Communities ◽  
Digital Elevation ◽  
River Flood ◽  
Vulnerability Maps ◽  
River Banks

Flood remains one of the most common natural disasters. Its rate of occurrence and the associated destructive tendency are on a rising scale across the globe. Flood risk may increase due to human activities. It could also decrease by appropriate flood management and planning. However, this requires upgraded and newly generated reliable and up to date floodplain and flood vulnerability maps. Hence, this study analysed the Niger-Benue river flood risk and vulnerability of 256 communities in Kogi State. The aim is to generate reliable up to date flood vulnerability maps that categorises the communities into different vulnerability zones and identify likely locations for erecting flood shelter/refugee camps during flood events in the State. Shuttle Radar Topography Mission (STRM) Digital Elevation Datasets, the spatial location of 256 communities, shapefiles of Kogi State’s administrative boundaries and Niger-Benue river basin were among the datasets acquired for the study. The Digital Elevation Model (DEM) of the study area was created to depict topography and the heights of each component of the terrain. Also, a 3km buffer distance was created around the Niger-Benue river and four vulnerability zones were defined based on the terrain and proximity components of each community. Furthermore, choropleth maps were generated for each vulnerability zone based on the number of communities per Local Government Area (LGA). Findings of this study revealed that out of the 256 sampled communities, 161 representing 62.89% are exposed to varying degrees of vulnerability due to Niger-Benue flooding. Out of these, 33 (12.89%) are highly vulnerable, whereas each of the vulnerable (64) and marginally vulnerable (64) communities accounted for 25%. The rest 37.11% constituted the not vulnerable communities (95). Out of the highly vulnerable communities, 27.27% accounted for those located on river banks and 72.73% for those located within a 3km distance from the river. The majority of the riverbank communities were found in Kogi, Lokoja and Ajaokuta LGAs. Igalamela Odolu, Kogi, Ofu and Bassa were among the LGAs with a high number of vulnerable communities. The not vulnerable communities were mostly located around the Agbaja Plateau and Okoro-Agbo hills in Ijumu, Kabba/Bunu and Yaba East LGAs. It was concluded that the 9 communities (Ajaokuta, Eroko, Iche, Jamata, Numai, Okume, Agodo, Denbor and Gunji Twaki) located on river banks are exposed to the highest level of flood risk and invariably, the devastating impact of flood in Kogi State. Most communities in Ijumu, Kabba/Bunu and Yaba West LGAs are less likely to be affected by Niger-Benue River flooding. It is therefore recommended that communities within the highly vulnerable zones, beginning with the 9 located on river banks should be relocated to higher terrains. Also, future settlement development should be discouraged in the zone by the collaborative efforts of the State and LGA authorities. Further studies should be conducted around Ijumu LGA in view of identifying the most suitable locations for possible flood shelter/refugee camp development in the study area.

STUDY OF THE LANDSLIDE MORPHOLOGY BASED ON GNSS DATA AND AIRBORNE SOUNDING (ON THE EXAMPLE OF A SECTION OF THE PROTVA RIVER VALLEY)

2018 ◽  
Vol 12 (5-6) ◽  
pp. 50-57 ◽  
Author(s):  
I. S. Voskresensky ◽  
A. A. Suchilin ◽  
L. A. Ushakova ◽  
V. M. Shaforostov ◽  
A. L. Entin ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Geodetic Network ◽  
Aerial Survey ◽  
River Valley ◽  
Ease Of Use ◽  
Digital Elevation ◽  
Loose Deposits ◽  
Positioning Method ◽  
Landslide Body ◽  
Elevation Model

To use unmanned aerial vehicles (UAVs) for obtaining digital elevation models (DEM) and digital terrain models (DTM) is currently actively practiced in scientific and practical purposes. This technology has many advantages: efficiency, ease of use, and the possibility of application on relatively small area. This allows us to perform qualitative and quantitative studies of the progress of dangerous relief-forming processes and to assess their consequences quickly. In this paper, we describe the process of obtaining a digital elevation model (DEM) of the relief of the slope located on the bank of the Protva River (Satino training site of the Faculty of Geography, Lomonosov Moscow State University). To obtain the digital elevation model, we created a temporary geodetic network. The coordinates of the points were measured by the satellite positioning method using a highprecision mobile complex. The aerial survey was carried out using an unmanned aerial vehicle from a low altitude (about 40–45 m). The processing of survey materials was performed via automatic photogrammetry (Structure-from-Motion method), and the digital elevation model of the landslide surface on the Protva River valley section was created. Remote sensing was supplemented by studying archival materials of aerial photography, as well as field survey conducted immediately after the landslide. The total amount of research results made it possible to establish the causes and character of the landslide process on the study site. According to the geomorphological conditions of formation, the landslide refers to a variety of landslideslides, which are formed when water is saturated with loose deposits. The landslide body was formed with the "collapse" of the blocks of turf and deluvial loams and their "destruction" as they shifted and accumulated at the foot of the slope.

Urban Flood Mapping

2017 ◽  
Author(s):  
Indra Riyanto ◽  
Lestari Margatama
Keyword(s):  
Natural Disasters ◽  
Satisfying Condition ◽  
Three Dimensions ◽  
Urban Flood ◽  
Digital Elevation ◽  
Elevation Data ◽  
Recent Occurrence ◽  
Elevation Model ◽  
Digital Elevation Model Data ◽  
Potential Area

The recent degradation of environment quality becomes the prime cause of the recent occurrence of natural disasters. It also contributes in the increase of the area that is prone to natural disasters. Flood history data in Jakarta shows that flood occurred mainly during rainy season around January – February each year, but the flood area varies each year. This research is intended to map the flood potential area in DKI Jakarta by segmenting the Digital Elevation Model data. The data used in this research is contour data obtained from DPP–DKI with the resolution of 1 m. The data processing involved in this research is extracting the surface elevation data from the DEM, overlaying the river map of Jakarta with the elevation data. Subsequently, the data is then segmented using watershed segmentation method. The concept of watersheds is based on visualizing an image in three dimensions: two spatial coordinates versus gray levels, in which there are two specific points; that are points belonging to a regional minimum and points at which a drop of water, if placed at the location of any of those points, would fall with certainty to a single minimum. For a particular regional minimum, the set of points satisfying the latter condition is called the catchments basin or watershed of that minimum, while the points satisfying condition form more than one minima are termed divide lines or watershed lines. The objective of this segmentation is to find the watershed lines of the DEM image. The expected result of the research is the flood potential area information, especially along the Ciliwung river in DKI Jakarta.

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