Flood mapping susceptibility based on Geographic Information Systems (GIS) and the Analytic Hierarchy Process (AHP) method in Bol, Lac Province, Chad, Central Africa

Abstract

<p class="MsoNormal" style="text-align: justify; line-height: 150%;"><span lang="EN-US" style="font-size: 10.0pt; mso-bidi-font-size: 11.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">Climate change, a major challenge of the 21st century, is increasing the frequency and intensity of urban flooding, particularly in Sahelian cities. In Bol, in the Lac province of Chad, this dynamic has increased the frequency and intensity of flooding, making this risk a recurring threat to the city in recent years. This study aims to map the physical vulnerability (susceptibility) to flooding in the city of Bol using an integrated approach combining remote sensing, geographic information systems (GIS) and the Analytic Hierarchy Process (AHP). Eight key physical factors (precipitation, altitude, slope, land use, distance to watercourses, soil type, drainage density and flow accumulation) were analy</span><span lang="EN-US" style="font-size: 10.0pt; mso-bidi-font-size: 11.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;">z</span><span lang="EN-US" style="font-size: 10.0pt; mso-bidi-font-size: 11.0pt; line-height: 115%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">ed and weighted using the AHP. The results show that 16.19% of Bol’s surface area is highly susceptible to flooding, and 28.08% is highly susceptible, concentrated mainly in low-lying areas and near watercourses. Surveys of 385 households confirm the recurrence of flooding and its significant impact on housing. The map produced is an essential decision-making tool for communities, decision-makers and urban stakeholders in planning actions to reduce current and future flood risks in the city of Bol. However, the lack of quantitative validation of the model is a methodological limitation, opening the door to future research incorporating uncertainty and exposure analyses.</span></p>