Print Email Facebook Twitter Title: Early implementation projects on flood control and irrigation in Bangladesh Title Title: Early implementation projects on flood control and irrigation in Bangladesh: Study of methods used for closing tidal channels - Study of methods for closing tidal channels; fifth interim report – Madargong closure Author Smith, E.C. Zwets, J. Corporate name Bangladesh Water Development Board Date 1980-08 Abstract The closure of the Madargong has been undertaken in the winter of 1979/80 as a stage of the "Study of Methods for Closing Tidal Channels". The closure has been taken up as an Early Implementation Project on Flood Control and Irrigation in Bangladesh. A team of four Dutch experts assisted the Bangladesh Water Development Board and also the contractor with the implementation. The closure has already been attempted twice without success by means of the local mata-method. The same fate was ultimately also allotted to the third attempt. The tidal channel has been closed by means of bottom protection mattresses, an underwater sill and a cofferdam filled with clay-filled gunny bags. The tidal range at the site is about 17' at spring tide and 6' at neap tide. The tidal prism during spring tide is about 5800 acre feet (7 million cub.m.). The channel cross-section below the average water level was about 7000 sq.ft. (650 sq.m.) with a width at the water line of 450 feet (140 m). More detailed information concerning tides, soils, cross-sections and work activities is given in Chapter 3. Vertical closure was implemented in two phases. Phase One consisted of the construction of a bottom protection and an underwater sill formed by dumping clay-filled gunny bags from barges which were subsequently covered with mattresses. Phase Two involved the construction of a jetty cum coffer dam with walls of bamboo piling. The actual closure was achieved by filling the cofferdam with clay-filled gunny bags. Chapter 4 gives more extensive information concerning the design and the execution of the closure works. The execution of the project encountered many problems, which are described in Chapter 4. In spite of these problems, the Madargong has been closed on March 26th, with a delay of one month according to the original time schedule. On 30th of March, however, a breach occurred; a part of the cross-dam washed away resulting in a gap with a width of 80 feet. Chapter 5 deals with the breaching and the planning of the closure of the breach. It was decided that this closure had to be effectuated before May 1lst in view of the deteriorating tidal and weather conditions. The chances to succeed were, however, found to be rather low in view of the amount of work to be done in a very short period, the required quantities of materials, the rather poor management of the contractor, and the approaching rainy season. This could not justify the investment of another 13 Lakh Taka (Tk 1,300,000). It was, therefore, decided to stop the work and to see what is left of the works after the rainy season. The experience obtained is described in a condensed form in Chapter 6. The overall conclusion is that the technical risks involved in a closure with local materials and manual labour can be reduced considerably by using the obtained experience. However, the risks introduced by the lack of management with the contractor are much more difficult to control. These risks must be accepted if the present program is continued. The introduction into the practice of elements of the traditional Dutch methods based on local materials and manual labour is an essential part of the program "Study of Methods for Closing Tidal Channels". Subject BangladeshMadargongClosure works Classification TPN4000 To reference this document use: http://resolver.tudelft.nl/uuid:36659e01-23cf-48b2-a9df-5b5776321c4c Publisher Bangladesh Water Development Board Part of collection Hydraulic Engineering Reports Document type report Rights © 1978 Netherlands Technical Assistance Programme Files PDF BWDB-5th interim-madargong.pdf 97.48 MB Close viewer /islandora/object/uuid:36659e01-23cf-48b2-a9df-5b5776321c4c/datastream/OBJ/view