Hydrologic modeling - Developing hydrologic GIS layers

The stream network was obtained from Digital Elevation Model (DEM) data sets using ESRI ArcGIS procedures and commands.
	Use FILL function to fill sinks (flaws) in the DEMs that are not areas of internal drainage. Determine flow directions using the FLOWDIRECTION function. Determine flow accumulation to each cell using the FLOWACCUMULATION function. Delineate the stream networks by choosing a flow-accumulation threshold value of >1,000. We used this value because it produced networks that approximated the networks of actual perennial stream segments in the two study watersheds. The following conditional GRID statement was used: STREAMNET = CON(FLOWACC > 1000, 1) Assign a unique number to each stream link that represents a channel segment (stream reach) that was used in the numerical flow model.
Hillshaded digital elevation model (30m resolution) of the East Little Calumet Watershed

For each segment in the stream network, contributing interfluve areas were calculated.
	Determine all cells associated with a stream segment using STREAMLINK. Calculate contributing interfluve areas associated with each stream segment in the networks using the WATERSHED function. Associate contributing areas with their receiving stream link for use in the numerical flow model.
Stream network and interfluve areas extracted from the DEM of the East Little Calumet River watershed.

The slope of each stream reach was calculated.

Determine from-nodes (upstream point) and to-nodes (downstream node) for each stream reach.
Using the node coverage and the data from the associated DEM, extract the elevation of the upstream and downstream points for each stream segment.
Using the node elevations and the length of each stream segment from the stream network coverage, calculate the slope of each reach:
Associate the slope value of each stream reach with the unique number assigned for each stream link for use in the numerical flow model.

NOTE: Each stream segment, which is bounded by two nodes, has a unique contributing interfluve area (example in yellow).