It may be concluded that out of 6 % annual silt deposition, 5 % silt deposition took place during the month between June and October and 1 % silt deposition during the month between November and May. The rate of sedimentation was then calculated and found to be 16,328.82 m 3/month silt deposition during monsoon and 11,109 m 3 silt deposition during non monsoon period. The total volume of silt accumulated has been estimated 277,589.92 m 3. Due to the increased capacity of the channel in the middle part possibility of flood has also decreased. Also, the increased salinity of the river helped in cultivation of different species of fishes, which are socio economically relevant in the adjoining areas. The river velocity in the top strata is 0.3 m/s from model and the river regained its ecological flow. middle part showed impacts which were positive in ways more than one. The de-siltation of the stretch of Ichamati river under survey i.e. Good quality in situ measurements of river hydraulics (cross section, slope, flow) were available only for the upstream and middle stream flood prone region of the basin. In this study, we set up the one dimensional river analysis system (RAS) model of the hydrologic engineering center (HEC) over the stream network of the Ichamati river basins. But one can use proxy approaches relying mostly on remote sensing data from space platforms for the purpose. The measurements of river bed depth/slope, water quality (river cross section), floodplain mapping and boundary condition flow are essential for the set up of a river model. Such river models are often an important component of flood forecasting, tidal fluctuation system that forecasts river levels in flood prone regions of the middle stream of Ichamati river. If a user inserts geospatial coordinates for a lateral structure, not only will it be drawn geospatially correct, but HEC-RAS will figure out how elements (1D cross sections and 2D Face Points) are connected to the lateral structure based on its spatial location.The physically-based hydrodynamic model can simulate the water flow dynamics of a stream network against time varying boundary conditions that can be implemented for the case of Ichamati River. User can use the Measure Tool to draw a line that would represent the lateral structure geospatial X and Y coordinates, then paste those coordinates into the Lateral Structure Centerline Table (This is optional). Under the menu item labeled GIS Tools, there is now a table option called Lateral Structure Centerlines Table. HEC-RAS now has the option to have georeferenced lateral structures. The user also has the option to evaluate levee breaching.
Water that goes above the levee will be modeled as weir flow. The area behind the levee could be represented with either a 2D Flow Area, storage area (or combination of interconnected storage areas), or another river reach.
In general, the user should end their cross sections at the inside top of the levee, and then use the lateral structure option to represent the top of the levee along the stream. The lateral structure option can also be used to model a levee. Lateral structures can be connected to storage areas, 2D Flow Areas, or another river reach. The rating curve can be used to represent an entire structure or a particular outlet that could not be modeled with HEC-RAS. The diversion rating curve can be used alone, or in conjunction with the other hydraulic outlet types. The culverts can be any of the available shapes from the standard HEC-RAS culvert capability. The spillway crest of the gates can be modeled as either an ogee shape, broad crested weir, or sharp crested weir shapes. The gated spillways can have either radial gates (often called tainter gates), vertical lift gates (sluice gates), overflow gates (open to the air or with a covered top), or user defined gate curves.
The user can set up a single lateral weir, a weir and separate set of gates, a weir and group of culverts, or any combination of weir, gates, culverts, rating curves, and a time series outlet. At any lateral structure HEC-RAS has the ability to model lateral weirs, gated spillways, culverts, diversion rating curves, and an outlet time series.