We used digital elevation model (DEM) data as a surrogate for data that were not available at an appropriate spatial scale or did not cover the study area uniformly. Specifically, we used the DEM data to derive a streams layer, stream gradient, stream confinement, and ultimately stream channel types.

There are, however, limitations to DEM-derived data and we offer these data layers as 'stand-in' data layers until better data become available. One limitation is that DEM cells are 10 X 10 m. This is far too coarse to capture many stream attributes (e.g., confinement). On the other hand, the DEM-derived layers are of a uniform spatial scale and depict stream attributes at the spatial scale of the DEMS. Therefore, these layers are internally consistant with one another. In addition, many fine-scale changes in stream gradient and slope are captured in these modeled layers, if the computer models are correct, that are not otherwise available. For example, the DEM-derived stream gradient layer shows where there may be biologically important gradient breaks along stream reaches -- breaks that would not be mapped using a more conventional approach.

The real test, however, is to determine how well the computer generated DEM-derived data represent what is in the field. Therefore, it will be particularly useful to have field teams groundtruth these layers.

Please address questions or comments to:

Dr. Ralph Garono
Principal Investigator
Earth Design Consultants, Inc.
rgarono@earthdesign.com

Laura Brophy
Principal Investigator
Green Point Consulting
brophyl@peak.org | homepage