Causes of failure of submersible embankment and its impact on the haor area a case study of karchar haor project

Abstract

Flash floods are generated in the steep, upland catchments in the north-eastern region of Bangladesh adjacent to the hilly region of India. The single crop, Boro, is cultivated in this region, which remains under uncertainty of harvesting due to early flash floods. When early (pre-monsoon, up to 15th May) flash floods damage the only crop, then inhabitants remain in a distress condition until the next year’s harvest. This is a major concern for the area as well as for the whole nation. To save the crops from pre-monsoon floods BWDB have implemented number of Haor Projects in the area starting from the early sixties. The main component of the Haor Projects is the submersible embankments along with other components like sluices, regulators etc. Submersible embankments are constructed to protect the crops from the pre-monsoon floods upto May 15. The design levels of submersible embankments have been determined considering 1:10 year pre-monsoon flood. The embankments in different Haors have been constructed at different times; some in the early sixties and some recently. The early flash floods of April 2010 caused a colossal damage to lives, crops and properties of the Haor area. Almost all the Boro rice was damaged by flash flood and therefore the economy of the Haor people was severely affected. Karchar Haor is one of the Haors which is surrounded by submersible embankment and in where the Boro rice was also damaged severely by early flash flood of 2010. This study has been conducted to assess the causes of failure of Karchar Haor submersible embankment by taking into consideration the adequacy of design crest level, quality of regular repair and maintenance, effect of change of rainfall and water level pattern etc. This study also assesses the impact of damage and on how the farmers cope with the situation considering the post-damage economic activity. Also a strategy has been formulated for management of the Karchar Haor area. Maximum pre-monsoon flood level at Station Saktiarkhola (WL-131), Sunamgonj (WL-269) and Shukevpur (WL-072B) in the Jadukata, Surma and Chalti River respectively with 1 in 10 year frequency was estimated. The design crest level of the embankment was then determined (BWDB, 1996) and was compared with the existing crest level in order to assess the adequacy of existing crest level. The HFL (High Flood Level) in 2010 of the surrounding rivers was compared with the existing crest level to check the adequacy of the embankment. Key Informant Interview (KII) was conducted with BWDB officials at Sunamgonj to find out, if there is any other reason of failure of submersible embankment. The impact of damage in agriculture, fisheries and livelihood was assessed and a management strategy was introduced for better future maintenance. Different PRA tools like Focus Group Discussion (FGD), Group Discussion (GD), Key Informant Interview (KII) etc have been used to generate the information regarding the research. It is found that the design crest level is more or less adequate but poor quality repair and maintenance work is the main cause of failure. In 2010 boro production of Karchar haor declined from 11400 metric ton to 1080 metric ton. This means flash flood damaged 90% boro crops of this area in 2010. The damage caused heavy impact on livelihood. The HHDI value of this area has reduced from 0.48 to 0.37 after occurrence of damage. The people of haor area are resilient and able to cope with the damage situation. Management of Karchar Haor through structural intervention is required in order to reduce the vulnerability of damage and thus its impact on the livelihood.