The derivation of stream channel types is dependent on DEM-derived stream gradients and DEM-derived stream confinement. The digital elevation model (DEM) cells are 10 X 10 m and the GIS methods used to derive confinement and gradient probably obscure important topographic information necessary to better describe these two stream attributes. In addition, stream gradient was calculated in degrees and had to be converted to percent slope. This resulted in stream slope categories of 0-2%, 2-4%, 4-8%, etc. Nevertheless, GIS data depicting stream gradient, stream confinement, stream channel types, and even the streams themselves were not available at an appropriate spatial scale for the entire study area. Therefore, we used the DEM-derived data to generate a first approximation of these important stream characteristics.

Summary of Stream Channel Types for the entire study area.

Channel Type	Length (m)	%
VH	1,918,904.4	30.7
SV	975,285.6	15.6
MV	850,160.9	13.6
MV-U	686,758.8	11.0
MM	653,066.5	10.4
FP2-3	416,717.8	6.7
FP1	356,134.0	5.7
EL	136,914.6	2.2
MC	124,490.7	2.0
LC	61,525.3	1.0
ES	40,399.8	0.6
SV-U	33,872.8	0.5
VH-U	5,761.5	0.1
TOTAL	6,259,992.6	100.0

We recommend that information in these data layers be field checked as soon as possible. Comparisons that we have made with existing data suggest that these DEM-derived layers may capture topographic detail that is often missed in more conventional methods.

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