Flood Vulnerability Assessment in the Hilly Districts of Southeastern Bangladesh: A Multi-Criteria Approach    

Flood Vulnerability Assessment in the Hilly Districts of Southeastern Bangladesh: A Multi-Criteria Approach | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 21 January 2026 V1 Latest version Share on Flood Vulnerability Assessment in the Hilly Districts of Southeastern Bangladesh: A Multi-Criteria Approach Authors : Golam Morsad 0009-0003-4847-4037 [email protected] , Md. Tahseen Ahmed , and Sonia Binte Murshed 0000-0002-9775-3601 Authors Info & Affiliations https://doi.org/10.22541/au.176903380.00545667/v1 175 views 49 downloads Contents Abstract Objectives Study Area Description Methodology Flood Vulnerability Factors Major Findings Conclusion References Acknowledgement Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Floods are among the most frequent and damaging climate-related disasters globally, with risks projected to rise due to changing rainfall patterns, land use shifts, and growing population in hazard-prone areas. The hilly districts of southeastern Bangladesh face growing flood risk due to intense monsoon rainfall, steep terrain, and expanding settlements. Districts such as Chittagong, Cox’s Bazar, Rangamati, Bandarban, and Khagrachari have experienced increasingly frequent flood events. However, spatial assessments that integrate both physical and social factors remain limited across this region.This study assessed flood vulnerability using a multi-criteria approach. Twelve indicators were considered, including elevation, slope, topographic wetness index (TWI), soil type, drainage density, proximity to waterbodies, rainfall, land use, population density, literacy rate, household numbers, and agricultural land. These were weighted using AHP and analyzed spatially.Findings show that areas within 20 km of major waterbodies, particularly in Chittagong, Cox’s Bazar, and parts of Rangamati, are highly flood-prone due to exposure to surface water bodies. Regions with drainage density above 45 m/k.m 2 face increased runoff pressure, especially in downstream zones of Chittagong and Cox’s Bazar. TWI values >4 indicate high moisture accumulation, mostly in Rangamati and eastern Chittagong. Steep slopes above 15 o and elevations exceeding 300 meters, prominent in Rangamati and Bandarban, contribute to flash flood risk through rapid runoff. Districts receiving over 2800 mm of rainfall during the 2023 monsoon, including Chittagong, Cox’s Bazar, and Khagrachari, also show elevated hazard exposure. Areas with clay and silt loam soils, such as in Bandarban and Rangamati, are more vulnerable due to poor infiltration. Social vulnerability is intensified in zones with dense households, extensive agricultural activity, and low literacy, particularly in Chittagong and Khagrachari.The final vulnerability map shows that over 50% of Chittagong and Cox’s Bazar fall into moderate to high-risk zones. About 20% of Rangamati is highly vulnerable, while Khagrachari and Bandarban show comparatively lower exposure. The results provide a spatial basis for prioritizing flood preparedness across the hilly southeast. Objectives 1. To assess flood vulnerability in the hilly districts of southeastern Bangladesh using 12 physical and socioeconomic indicators. 2. To determine the relative importance of flood-influencing factors by assigning weights through the Analytic Hierarchy Process (AHP). 3. To develop a spatial flood vulnerability map to identify high-risk zones and support targeted disaster risk reduction and planning. Study Area Description The study area covers Southeastern Bangladesh, encompassing the districts of Chittagong, Cox’s Bazar, Rangamati, Bandarban, and Khagrachari. The region covers a total area of approximately 21,120 km² , with a combined population of roughly 13.8 million according to the 2022 census (Bangladesh Bureau of Statistics [BBS], 2022). Geomorphologically, the region spans the Chittagong Coastal Plain and the Chittagong Hill Tracts (CHT), characterized by complex topography ranging from coastal lowlands to steep, forested hills reaching elevations of up to 1,000 meters (Alam et al., 2020). The study area experiences a tropical monsoon climate with high rainfall variability, making it highly susceptible to hydro-meteorological hazards, including cyclones, storm surges, and frequent flash floods (Chowdhury et al., 2021). The region is hydrologically significant, hosting major river systems such as the Karnaphuli, Sangu, and Matamuhuri, which drain into the Bay of Bengal and support critical ecosystems including mangroves and hill forests. However, rapid urbanization, extensive deforestation, and the impacts of climate change have significantly exacerbated environmental vulnerability across these administrative districts (Hasan et al., 2021). Study area map Methodology Source of Data: Factors Sources Elevation Slope ASTER Dem (30m) TWI Drainage density Proximity to waterbodies Rainfall CHRIPS satellite Land use Landsat-8 Population density Literacy rate Household numbers "Bangladesh Bureau of Statistics (BBS)" Agricultural land Soil type "Bangladesh Agricultural Research Council (BARC)" Steps: • Selected 12 flood-related indicators representing physical and socioeconomic conditions (elevation, slope, TWI, soil type, drainage density, proximity to waterbodies, rainfall, land use, population density, literacy rate, soil types, household numbers, and agricultural land). • Collected and prepared spatial datasets from satellite imagery and secondary sources. • Standardized all datasets to a common spatial resolution and projection. • Land use classification from landsat-8 image • Applied the Analytic Hierarchy Process (AHP) to assign weights to each indicator based on their relative influence on flooding. • Normalized and reclassified all indicator layers to a common scale of 1–5 (very low to very high contribution to vulnerability). • Integrated all weighted layers using weighted overlay analysis to generate a Flood Vulnerability Index (FVI) map. • Classified the final vulnerability map into five categories: Very Low, Low, Moderate, High, and Very High vulnerability. Flood Vulnerability Factors All vulnerability factors maps Major Findings • Chattogram: ~35% of the area is very high vulnerable, 25% high, 25% moderate, 10% low, 5% very low — significant flood risk concentrated in low-lying areas. • Cox’s Bazar: ~40% very high, 30% high, 20% moderate, 10% low, <1% very low — highest vulnerability in coastal and river-adjacent zones. • Rangamati: ~5% very high, 15% high, 40% moderate, 30% low, 10% very low — mostly moderate to low vulnerability in hilly terrain. • Bandarban: ~5% very high, 15% high, 35% moderate, 35% low, 10% very low — hilly areas reduce flood risk, moderate risk in valleys. • Khagrachari: ~3% very high, 10% high, 35% moderate, 40% low, 15% very low — largely low to moderate vulnerability due to elevation and slope. Flood Vulnerability map of Southeastern Bangladesh Area for each vulnerability classes Conclusion • Flood vulnerability varies widely across the hilly districts, highlighting the need for district-specific planning and interventions. • High-risk zones in Chattogram and Cox’s Bazar require immediate attention for flood preparedness, early warning systems, and resilient infrastructure. • Moderate to low-risk areas in Rangamati, Bandarban, and Khagrachari still need monitoring, especially in valleys and low-lying settlements, to prevent future losses. • The multi-criteria approach combining physical (elevation, slope, TWI, drainage, soil, rainfall) and social (population, literacy, household, agriculture) factors allows a holistic assessment of flood vulnerability. • The methodology provides a replicable framework for assessing flood risk in other hilly or complex terrains, supporting long-term disaster risk reduction strategies. • Findings can guide policy makers, urban planners, and disaster management authorities in prioritizing resources, designing mitigation measures, and planning sustainable land use. • The spatial maps can serve as decision-support tools for future climate adaptation, community awareness programs, and infrastructure planning in flood-prone regions. References Alam, M. S., Baky, M. A. A., & Sultana, N. (2020). Assessment of land use and land cover changes in the Chittagong Hill Tracts of Bangladesh using remote sensing and GIS. Environmental Monitoring and Assessment, 192 (10), 1–18. https://doi.org/10.1007/s10661-020-08574-z Ahmed, B., Rahman, M. S., Sammonds, P., Islam, R., & Uddin, K. (2020). Multi-hazard susceptibility assessment in the Chittagong Hill Tracts, Bangladesh. Geomatics, Natural Hazards and Risk, 11 (1), 1630–1662. https://doi.org/10.1080/19475705.2020.1810793 Bangladesh Bureau of Statistics (BBS). (2022). Population and Housing Census 2022: Preliminary Report . Statistics and Informatics Division, Ministry of Planning, Government of the People’s Republic of Bangladesh. Chowdhury, M. K., Rahman, M. M., & Khan, A. S. (2021). Hydrological modeling of flash floods in the hilly regions of Bangladesh: Challenges and prospects. Journal of Hydrology: Regional Studies, 34 , 100791. https://doi.org/10.1016/j.ejrh.2021.100791 Dewan, A. (2013). Floods in a Megacity: Geospatial Analysis of Environmental Hazards and Resilience . Springer Science & Business Media. Hasan, S. S., Hossain, M. S., & Islam, M. T. (2021). Impact of urbanization and climate change on the environmental vulnerability of coastal Bangladesh. Science of the Total Environment, 765 , 144437. https://doi.org/10.1016/j.scitotenv.2020.144437 Hirabayashi, Y., Mahendran, R., Koirala, S., Konoshima, L., Yamazaki, D., Watanabe, S., Kim, H., & Kanae, S. (2021). Global flood risk under climate change. Nature Climate Change, 3 (9), 816–821. IPCC. (2023). Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland. Saaty, T. L., & Vargas, L. G. (2012). Models, Methods, Concepts & Applications of the Analytic Hierarchy Process (2nd ed.). Springer New York. https://doi.org/10.1007/978-1-4419-0604-5 Acknowledgement This research was presented at the AGU Annual Meeting 2025 (New Orleans). The interactive poster presentation, including high-resolution spatial maps and detailed multi-criteria analysis, can be accessed via the official AGU iPosterSessions gallery: Link: https://agu25.ipostersessions.com/default.aspx?s=AD-1E-B1-3A-AC-04-E7-F4-06-F2-55-D5-32-AC-A6-FB Information & Authors Information Version history V1 Version 1 21 January 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords ahp method bangladesh flood vulnerability gis/remote sensing spatial analysis Authors Affiliations Golam Morsad 0009-0003-4847-4037 [email protected] View all articles by this author Md. Tahseen Ahmed View all articles by this author Sonia Binte Murshed 0000-0002-9775-3601 View all articles by this author Metrics & Citations Metrics Article Usage 175 views 49 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Golam Morsad, Md. Tahseen Ahmed, Sonia Binte Murshed. Flood Vulnerability Assessment in the Hilly Districts of Southeastern Bangladesh: A Multi-Criteria Approach . Authorea . 21 January 2026. DOI: https://doi.org/10.22541/au.176903380.00545667/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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