Development of a Methodology for Accurate Represrentation of Rivers in Two and Three Dimensions

The proposed research intends to develop a methodology in GIS that enables one to accurately represent the geometry of river channels in two and three dimensions. Hydraulic data are used to run a finite element hydrodynamic model and the results of the hydrodynamic model and the biological data are used to predict the impact of flow alteration on fish species habitats in the river. Hydrodynamic modeling plays a vital role in the instream flow studies and its results are dependent on the accurate representation of river geometry. The riverbed is usually created by interpolating field data using spatial interpolation methods in GIS. Presently available spatial interpolation tools in GIS are designed for land surface, and they do not work very well for riverbed because the river bathymetry changes significantly in lateral direction as compared to the direction along the flow. It is proposed to use additional coordinates for the representation of data points on a river channel. In the new coordinate system, each point on the river is where m is the distance along the centerline of the river and r is the perpendicular distance from the centerline of the river. Thus, it is possible to represent a sinuous river as a straight river using only the m and r coordinates and to think of it as a volumetric object in (m,r,z) coordinates. In order to represent the channel bed accurately, it is proposed to develop some new methods in GIS so that the river is considered as a linear feature with its unique characteristics. This involves iii modifications to some to the existing methodologies that are available in GIS, such as inversed distance weighting and spline. Some geomorphologic studies to address the issues such as the effect of high flows on the riverbed are also proposed. This research is expected to provide a helpful tool in developing river surfaces from sparsely collected field data and examines the importance of river geometry in modeling the hydrodynamics of the river. It is also intended to examine how the studies done on a small reach of a river can be used to predict the river morphology at some other locations along the river network.