Bangladesh has about 24,OOO km of rivers,haors & canals that together cover about'to of the country's surface. Most part of the country is linked by a complex network of waterways, which reaches its extensive size in the monsoon period. About 6,000 km. of ine classified river length is navigable by mechanized vessels during monsoon period which shrinks to about 3,900 km. during the dry peribd. Furthermore, the country hasai coastline of 508 km. facing the Bay of Bengal. These waterways provided the cheap and convenient means of communication and flow of commerce. Bangladesh Inland Water Transport Authority (BIWTA) is responsible to provide navigational safety along the waterways system. For this purpose' BIWTA puts up conservancy aids such as buoys, beacons, undertakes dredging, salvage operations etc, issues periodic river notices to mariners, publishers annual tide tables, provides horizontal & vertical clearances of the overhead power lines/bridges etc, to the user of the waterways. To undertake all these activities, hydrographic charts with updated and accurate depth information are the basic necessities. The Department of Hydrography, BIWTA has to undertake hydrographic survey and charting of Inland and coastal waterways on regular and routine basis.

During the last decade, the morphological behavior of the river and river bed profile have been greatly changed due to the natural hazards ard human interference such as lifting of water from inside and outside the country, construction of roads, barrage, bridge, dikes etc. For this reason, the SHWL and SLWL have been changed and navigation became risky. So, needless to say the updating of SHWL & SLWL is very much essential. Length of navigable waterways has been reduced over the last five decades. One of the main reasons of declining length of waterways is construction of installations along the bank of inland waterways or over the river. Impacts of construction of such installations have led to a reduced vertical and horizontal clearance to such an extent that substantial lengths of waterways have been abandoned by vessels for navigation

BIWTA had to take up the matter with the Govemment of the People's Republic of Bangladesh. Subsequently government made a provision that all agencies will have to take vertical and horizontal clearances from BIWTA prior to prepafing design of any Project for construction. of any kind of installation along the bank or over the river. As such, situation improved a little bit not to the satisfaction or need. It was found that some agencies constructed installation avoiding vertical and horizontal clearances awarded by BIWTA.

The main objective of the this project is to establish the navigational datum above a chosen common reference level (MSL) by studying the variation of the water levels and finding levels at 95% and 57% exceedance probabilities as well ai reclassify the existing BIWTA navigation routes and determine the actual horizontal and vertical clearances for bridges and other installations beside the rivers.