Application of Analytic Hierarchy Process and Geographic Information System Techniques in Flood Risk Assessment: A Case of Ofu River Catchment in Nigeria

Abstract

Flood risk assessment of Ofu River Catchment in Nigeria was carried out by integration of thematic maps in ArcGIS 10.2.2. Analytic Hierarchy Process (AHP) was applied in the decision making and ranking of flood causative factors before their integration for development of hazard map in ArcGIS. The social and physical vulnerability of the catchment were considered in the development of the vulnerability map. The flood risk map was developed as a product of the hazard and vulnerability map. The results showed that the land areas within the Very High and High Risk zones were respectively 163.07 km 2 and 392.63 km 2 with Igalamela/Odolu Local Government Area (LGA) accounting for about 62% and 31% respectively. A total of 19, 034 and 47,652 persons are respectively at very high and high risk of flood within the catchment. Oforachi community in Igalamela/Odolu LGA and Ejule Ojebe Community in Ibaji LGA both in Kogi State are respectively at Very High and High Risk of Ofu River flood. High Impacts were recorded by about 35% and 52% of Oforachi Community during the 1995 and 2000 historical flood events. A watershed management plan is therefore required to prevent the serious damage experienced in previous flood events.

Multi-Hazard Risk Assessment at Community Level Integrating Local and Scientific Knowledge in the Hodh Chargui, Mauritania

“…Contrary to the indications of the Sendai framework (2015) [2], the integration of knowledge is still unusual on a regional scale. The systematic review highlighted that only one assessment out of four published on tropical African regions estimated the probability of flooding or drought [1,3,11,18,19,27]. This is likely to result from poor access to local data.…”

“…These measures, compared with those proposed by the literature, are more specific and directly implementable ( Table 9). Ground pad with pill way [10] Dry stone cords [10] Dry stone thresholds [10] Tabias [10] Creek banks planting [13] Increasing tree vegetation [4] Avoid building in flood prone areas [14] Fluvial flood Gabion wall to protect riverbank Dykes, embankments, ditches [6,13,21] Resettlement [6,21] Early warning [18,19,21,25] Environmental education [6,24] Land use planning [24] Watershed management plan [19] Flood monitoring [24] Emergency preparedness [19]…”

“…However, the risk assessments published on tropical Africa (Table 1) deal with a single hazard at a time, which in 90% of cases, is the flood hazard and, for the remainder, the drought hazard. [7,8,11,[18][19][20][21][22][23][24][25]] Drought [26,27] Meteorological drought -Hydrological drought [27] Probability [1,3,11,18,19,27] Adaptive capacity [1,9,17,18] Evaluation - [1,4,7,11,13,19,21] The published assessments usually follow two approaches. The first approach performs distance assessments through satellite images, digital elevation models, soil maps, precipitations, and stream-flow datasets.…”

Using Multiple Index Comprehensive Method to Assess Urban Rainstorm Disaster Risk in Jiangsu Province, China

“…Lyu [9] proposed a risk assessment system based on rainy season, average rainfall, river proximity, and other rainstorm indices. Alfa [10] developed a flood risk assessment system of Ofu River catchment in Nigeria, including elevation, slope, proximity, and soil type. Weerasinghe [11] put forward the risk assessment system of rainstorm for the Western Province of Sri Lanka.…”

Using Multiple Index Comprehensive Method to Assess Urban Rainstorm Disasters Risk in Jiangsu Province, China

“…Lyu et al [12] selected rainy season, average rainfall, average rainy days, elevation and slope, river proximity, river density, land use, metro line proximity, metro line density and road network proximity and density to construct a risk assessment system of metro systems, and took Guangzhou metro system as an example to conduct an empirical study. Alfa [13] proposed a flood risk assessment of Ofu river catchment in Nigeria, including elevation, slope, proximity and soil type. Weerasinghe et al [14] put forward the risk assessment system of rainstorm for the Western Province of Sri Lanka, and use a statistical expression of hazard, exposure and vulnerability to assess the combined flood risk levels.…”