Stream Crossing Replacements on Timber Harvest Sites Cause Minimal Erosion

The Issue

Thousands of road-stream crossings (i.e., culverts) in California are either being removed altogether or replaced with better designed, more functional structures. The primary impetus for this is to reduce the potential for sediment delivery to streams caused by catastrophic crossing failures during stressing weather events. Although there has been some study of the post-construction stream channel erosion caused by removing crossings, there have been no published studies addressing these impacts for replaced crossings.

What Has ANR Done?

UC Extension Forestry Specialist Richard Harris obtained funding from the DANR Core Issues Grant Program to conduct research on the erosional response of stream channels to culvert replacements. Thirty sites were selected on the Hoopa Valley Indian Reservation and commercial timber lands owned by Green Diamond Resource Company and Pacific Lumber Company in Humboldt County. Data on stream channel morphology were collected immediately after culvert replacements and after the winter of 2005-06. Results indicated that there was very little erosion attributable to the construction. Effective mitigation measures were applied by the land managers to prevent serious impacts.

The Payoff

First California study on the erosional effects of stream crossing replacements accepted for publication.

This study documented that when deficient stream crossings are replaced with properly sized and designed structures, construction-related erosion and sediment delivery can be minimized if erosion control measures are implemented. This information will be useful to restorationists planning and executing stream crossing replacements and decommissionings. In particular, the study results demonstrate that investing a little extra money in erosion control measures pays off in sediment savings beyond those achieved by projects that ignore construction-related impacts.

Contact

Supporting Unit:

ESPM - Ecosystem Sciences
 
Richard Harris
201 Mulford Hall
Berkeley, CA 94720-3114
(510) 642-2360
(707) 301-5021 (cell)