乍得洪灾频率及影响分析（英）2026

Author Pierre E. BiscayeUniversité Clermont Auvergne, CERDI, CNRS, IRD and FERDI Research assistantsKesnel Azebaze Dongmo and Firida Gassissou SUMMARY Chad is consistently rated among the most vulnerable countries in the world to climate change.Increasing temperatures and precipitation are raising the threat of drought, flood, heatwaves, andvector-borne diseases.Infrastructure limitations and Chad’s young, poor, and rapidly growingpopulation amplify these vulnerabilities. Flood risk, in particular, is becoming increasingly salient inChad due to a series of devastating floods in recent years, notably in 2012, 2022, and 2024. This reportanalyzes flood risk in Chad as well as flooding incidence over the past 10-15 years using multiple datasources, to assess current and projected exposure to flooding and identify areas with significant risk.The findings aim to inform flood response strategies through the national safety net program andsupport broader efforts to strengthen resilience.Public Disclosure Authorized Contents 1Introduction1 2Flood risk in Chad3 2.1Present-day flood risk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42.1.1Mapping flood hazard in Chad. . . . . . . . . . . . . . . . . . . . . . . . . .42.1.2Mapping flood exposure in Chad. . . . . . . . . . . . . . . . . . . . . . . . .82.2Looking forward: increasing flood risk. . . . . . . . . . . . . . . . . . . . . . . . . .12 3Incidence of flooding 17 3.1Survey-reported flood incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223.2Remotely-sensed flood incidence. . . . . . . . . . . . . . . . . . . . . . . . . . . . .293.2.1Near real-time flood monitoring . . . . . . . . . . . . . . . . . . . . . . . . . .303.2.2Mapping historical flood incidence. . . . . . . . . . . . . . . . . . . . . . . .323.2.3Population exposure to detected flooding. . . . . . . . . . . . . . . . . . . .373.3Comparing flooding incidence between surveys and satellites . . . . . . . . . . . . . .41 4Estimating economic impacts of flooding in Chad49 4.1Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .504.1.1Flood exposure definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .524.2Empirical approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .544.2.1Identifying causal impacts of flood exposure . . . . . . . . . . . . . . . . . . .554.3Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .564.3.1Heterogeneity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .594.4Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60 5Conclusions AAdditional figures69BAdditional tables89CFlood management stakeholders in Chad100DMeasuring flooding by satellite106 List of Figures 1100-year flood depths in Chad under 2020 conditions (Fathom). . . . . . . . . . . .62Land exposed to→10 cm 100-year flood depths under 2020 conditions (Rogers et al)93Population density exposed to di!erent 100-year fluvial flooding hazards (Fathom).104Population exposed to→10 cm 100-year flood depths under 2020 conditions (Rogerset al) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125Projected changes in flood hazard from 2017 to 2100 . . . . . . . . . . . . . . . . . .136Projected change in 100-year flood depths in Chad under 2050 conditions (Fathom)147Projected changes in exposure to→10 cm 100-year floods (Rogers et al). . . . . . .158Historical exposure to flooding in Chad. . . . . . . . . . . . . . . . . . . . . . . . .189Average water flows across stations by month, over time . . . . . . . . . . . . . . . .1810Summary of flood exposure in ENSA surveys, 2016-2024 . . . . . . . . . . . . . . . .2411Flood exposure in ECOSIT surveys, 2015-2022. . . . . . . . . . . . . . . . . . . . .2712Estimated annual days of pixel flood exposure, 2012-2024. . . . . . . . . . . . . . .3413Deviations in days of annual flood exposure over space by year. . . . . . . . . . . .3614Areas of high population exposure to VFM-detected flooding. . . . . . . . . . . . .3815Annual population exposure to VFM-detected flooding . . . . . . . . . . . . . . . . .3916Mean annual population exposure by departement. . . . . . . . . . . . . . . . . . .4017ECOSIT panel community flood exposure by definition . . . . . . . . . . . . . . . . .53A1Chad agroecological zones and population density . . . . . . . . . . . . . . . . . . . .69A2Major rivers in Chad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69A3100-year flood depths in Chad under 2020 conditions (WRI and JRC). . . . . . . .70A410-year flood depths in Chad under 2020 conditions (WRI and JRC) . . . . . . . . .71A5Global population exposure to medium flood risk . . . . . . . . . . . . . . . . . . . .72A6Exposure to→10 cm 100-year flood depths under 2020 conditions (WRI) . . . . . . .73A7Projec