WMS - watershed map, watershed plan, watershed protection, watershed mapping

WMS - watershed map, watershed plan, watershed protection, watershed mapping

Conceptual Model

A conceptual model of the area your watershed exists in is created using a bounding polygon to define the limits of the area and stream arcs to identify the important channel data. The bounding polygon does not need to represent the actual watershed boundary; this will be determined later. The conceptual model will act like a "cookie cutter" in stamping out the region of the elevation data inside the polygon and then enforce the stream lines as triangle edges.

Creating the TIN

The conceptual model acts like a "cookie cutter" by triangulating the region of the elevation data inside the polygon and then enforcing the stream lines as triangle edges.

Outlet Point Creation

Outlet points can then be created anywhere along the stream for watershed and sub-basin delineation.

Basin Delineation

Flow paths from each triangle are then used to determine which triangles "flow into" the outlet point(s) and which do not. Once the boundary is determined, triangles outside can be deleted.

GIS Vector Data

GIS vector data are comprised of layers of points, lines, and polygons. The primary use of these kind of data in WMS is for modeling watersheds where points represent junctions (outlets of basins), lines represent the stream network, and polygons, the basin boundaries. WMS combines all three feature objects into a single coverage or layer called the drainage coverage. In addition to the drainage coverage, there are several other uses of GIS vector data in WMS as can be seen on the next several figures.

Storing the Results of DEM Delineation

After delineating a watershed and sub-basin boundaries using a DEM, the results are always converted to points (outlets), lines (streams), and polygons (boundaries) for more convenient data storage and manipulation.

Conceptual Model for Creating a TIN

The most important TIN quality for basin delineation is that triangle edges conform to important drainage features such as streams. By using GIS Vector data to establish streams and a "rough" boundary, a TIN well suited for basin delineation can be created.

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