Environmental Aspects of Clearing and Snagging

Abstract

Clearing and snagging is used as an economical technique for reducing the frequency and duration of high frequency flooding in environmentally sensitive locations. Riparian vegetation and the organic debris it produces influence stream morphology, water quality, and aquatic and terrestrial ecosystems. Complete clearing and snagging has detrimental effects on these stream characteristics. Modified clearing and snagging is less damaging to the environment. Major modifications involve: (1) Selective removal and disposal of trees and snags based on size, location, condition, and habitat value; (2) labor intensive construction techniques; (3) access controls; and (4) work scheduling to avoid fish spawning or other environmentally sensitive periods. Guidelines for modified clearing and snagging are discussed, and analytical approaches to estimating effects of vegetation and snags on flow resistance are reviewed.