Sunamganj is a north-eastern district of Bangladesh is considered a highly flood-prone haor area. Uttar Shreepur Union of Taherpur Upazila of Sunamganj District was selected to conduct the study to find out the causes behind the flash flood, situation analysis during and post-flood and different sectoral impacts of flash flood because these areas were flooded almost every year. Six focus group discussions (FGD) along with a total of 162 households were evenly targeted from six selected villages and a semi-structured self-explorative questionnaire was used to collect primary data. The study revealed that heavy rainfall (92.5%) and low land (53.13%) were the main causes of flood. The study also showed that transportation (84.37%) and agricultural (82.5%) sectors were the most affected, followed by water and sanitation (60%), housing (51.25%), and health (36.62%), respectively; among these, crops (89.37%) and animal husbandry (33.13%) were the most affected part of agriculture, followed by health sector, children (89.37%) and aged people (69.23%) were the most affected and the people were mainly suffered from cold and fever (98.13%), diarrhoea (80.63%), typhoid (27.5%), and dysentery (33.13%), respectively because of the crisis of pure drinking water and poor sanitation system. About 85% respondents stored normal food, followed by dry food (30%), medicine (25%) and water (0.63%), respectively to meet up post-flood food crisis. 62% respondents received flood warning signals by mobile phone (54.37%) followed by, radio/TV (41.87%), relatives (41.25%) and Upazila/Union Parisad (13.75%), respectively. However, various initiatives were taken by GOs and NGOs to build back a better immediate post-flood period. Finally, it is suggested that proper long-term steps should be taken to strengthen resilience and coping capacity for hydrological disasters in the study area.