Purpose

The landscape analysis model TOPAZ - TOpographic PArameteriZation - is used to define the watershed contour, delineate its drainage network and the corresponding subcatchments, and extract the channel network and subcatchment characteristics.  The digital representation of the delineated subcatchments is used in the computation of upland runoff and soil loss by watershed models.  The channel network is used as the starting point for the creation of the computational mesh for the channel simulation.  The landscape analysis establishes the data association between channel links and subwatersheds, necessary for the automated integration of the watershed and channel network models.

The CCHE1D Graphical User Interface (GUI) controls the user interaction with TOPAZ, simplifying its use and providing visual support for all operations.  The interface adds support for several GIS raster formats, generates maps to show the channels and subwatersheds, and allows interactive user input and control.

Channel Network and Subwatersheds

A Digital Elevation Model (DEM) is a matrix of equally spaced ground elevation values describing the terrain topography.  TOPAZ's algorithms analyze a raster-type DEM to identify drainage features and define channel networks whose appearance (channel density, minimum channel lengths and subwatershed areas) can be controlled by defining a value of drainage area necessary to form a channel, and by specifying a minimum length for source channels.  TOPAZ also generates a digital map of subcatchments that correspond to the channels of the network.

TOPAZ provides several pre-processing algorithms that prepare the DEM for analysis.  They include optional smoothing of the DEM, and the resolution of the indeterminate drainage in depressions and flat areas.  The CCHE1D interface helps the user in specifying these options as well as the two appearance-control parameters:

-        Critical Source Area (CSA):  The minimum upstream drainage area necessary to maintain a permanent channel.

-        Minimum Source Channel Length (MSCL):  The minimum length for source channels (channels without tributaries).

CCHE1D allows the creation of several sets of the above parameters, so that different parameter sets can be applied to a DEM, or conversely, the same set can be applied to several DEMs.  The interface allows the user to add, view, and modify parameter sets.  The user can use these sets to create several channel networks, which can be displayed simultaneously for convenience.

Once the drainage network is defined, the user provides the watershed outlet through an interactive map.  TOPAZ delineates the watershed contour for the given outlet, and defines subcatchments for each of the channel links within the watershed.

CCHE1D Database 

CCHE1D converts the output of TOPAZ from unformatted data files and tables into a relational database, which implements an enhanced description of the channel network and subwatersheds.  These database elements contain all the necessary information to establish connectivity between data related to the watershed modeling and to the channel processes modeling.  The database also includes graphical representations that are used in the creation of interactive maps and visualization, based on the functionality provided by the ArcView GIS program.