1.2 Background of the study area
Sunsari Morang Irrigation System (SMIS) is one of the largest irrigation project in Nepal which is aimed to irrigate 68000 ha of Sunsari and Morang district located in Eastern Terai area in Nepal.
Under bi-lateral agreement between Nepal and India in 1954, the system was designed and constructed by Government of India from 1964 to 1973 was handed over to Nepal in 1975 after two years of trial operation(Paudel, 2010). The water is withdrawn through a side intake from the left bank of the Koshi River. Koshi is known to be heavy sediment laden river, according to
Hooning, 2011, the river carries 59 million m3 of sand annually.
Paudel, 2010 suspects that based on the canal slope in SMIS, sediment transport criteria…show more content… The cohesive sediments are those which are finer like clay and have strong inter-particle attraction.
While non-cohesive sediments are those with weak inter-particle attraction like sand. The cohesive sediments are mostly found in suspension form in the canals whereas the non-cohesive sediments are found settled at the bed of the canals.
Different studies have been done for sedimentation in irrigation canals however most of the studies done are through 1D models which only gives the volume of sediment transport in the canal. But in order to fully understand the effect of gate operation on morphological and sediment transport processes one should be able know the distribution of the sediments along the cross-section of the canal as well. This can only be known if we use the 2D or 3D model for the analysis. Moreover, most of the studies have been concentrated in the non-cohesive sediments disregarding the behaviour of cohesive one. Conversely, a complete understanding of relation between gate operation and sedimentation can only be achieved if behaviour of both types of sediments are known in accordance to the canal