Delineation land use patterns are the paddy field,

Delineation of the basin and sub-basin boundary:

The Global Digital
Elevation Model (GDEM) will be used for
the delineation of the upper Meghna river basin boundary in the proposed study.
The said basin will be divided into some sub-basins and the sub-basin boundaries
will be developed using the ArcMap watershed delineation toolkit, based on
observed routing patterns, hydrological soil types and land use patterns. The DEM
data will be used as the base topographic input into the ArcSWAT (Soil and
Water Assessment Tool) model, will be needed to estimate the slope and contours
of the watershed. The estimated slope and contours of the river basin will help
to determine flow direction and
accumulation. Thus, a stream network will
be generated in the river basin, in which each individual reach (having a
node/outlet) drains a subbasin.

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Human activities change scenarios and hydrological soil assessment:

In the proposed
study, land use patterns change will be
assessed between 1997 and 2016. The land use patterns data may be collected
from the land use map developed by toposheet and remote sensing satellite
images. The land use map for 1997 will be considered as the base map when it
will be compared with land use patterns change. The observed land use patterns are
the paddy field, woodland, water body, dry
land, and vegetation. The future human
activities on the agricultural land will be predicted in the river basin
according to the trends of land-use patterns from past to present using the
CLUE (Conversion of Land Use and its Effects) model. The
future land use will be simulated in 2035 according to variation trend of
land-use patterns change between 1997 and 2016. The hydrological soil will be
surveyed from the soil map of 1997 and
2016 years, will be collected from different Government organizations in Bangladesh.

 

Assessment of human activities impact
on sediment yield:

A
”fixing–changing” method will be employed to determine the impacts of human
activities changes and different flow conditions on sediment yield (Tang et
al., 2011). The calibrated SWAT model will be operated for each land use map in
the study area for different periods,
where the DEM file and hydrological soil data will remain constant over the study period. The simulated results will be
used to determine the impacts of land use patterns change on the variation in sediment
yield at the basin scale and to quantify the contribution of the changes within
individual land use patterns to sediment yield changes at the sub-basin scale.

 

Assessment of flood hydrograph and peak discharge:

A hydrodynamic
model (HEC-RAS) will be used to estimate flood peak discharge and to create a flood map for the warning system. The model
needs hydrologic elements such as – the
delineation of sub-basin, sub-basin area,
stream length, elevation, and junction etc.,
will be developed by using ArcSWAT. In the proposed study, kinematic wave method will be used for flood
routing. The output from ArcSWAT model, streamflow, sediment yield, land use and rainfall data will be used as input to the HEC-RAS
model. Finally, the flood hydrograph, peak discharge, and flood map will be
determined at each junction under land use patterns change and different flow
conditions.