|Shields Jr, Fletcher|
Submitted to: Hydrobiologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 1998
Publication Date: N/A
Interpretive Summary: Channel erosion associated with stream bed lowering (incision) is especially severe and can destroy valuable habitat resources. Little infor- mation is available to guide projects that seek to rehabilitate streams damaged by this kind of erosion. Reaches of five northwest Mississippi streams were selected for a five-year study. During the study habitat restoration (or more accurately, rehabilitation) projects were constructed along two of the stream reaches. Existing erosion control structures were modified by adding stone to create deep, permanent pools. Willow posts were planted to speed recovery of streamside woody vegetation. The other three streams provided reference data, as two of them were incised but not rehabilitated, and the third was not incised. Rehabilitation projects were designed based on models of the way eroding channels change through time and recently published information about the interactions among stream fish hand their habitats. Rehabilitation increased pool habitat availability an made the treated sites more similar to the lightly degraded reference site. Before rehabilitation fish communities were dominated by small minnows, but after rehabilitation, the communities showed better balance, with larger sunfish and suckers appearing. Limited rehabilitation of incised stream corridors is possible for costs as low as 10% more than the expenditures required for traditional channel erosion controls without habitat considerations. This information will be especially useful to federal and state watershed planners.
Technical Abstract: Channel incision has major adverse impacts on stream corridor ecosystems. One-km reaches of each of five northwest Mississippi streams with contributing drainage areas between 16 and 205 km2 were selected for a five-year study. During the study two reaches were modified by adding woody vegetation and stone structure to rehabilitate habitats degraded by incision. The other three reaches provided reference data, as two of them were incised but not rehabilitated, and the third was not incised. Rehabilitation approaches were guided by conceptual models of incised channel evolution and warmwater stream fish community structure. Rehabilitation increased pool habitat availability, and made the treated sites more similar to the lightly degraded reference site. Fish communities generally responded as suggested by the aforementioned conceptual model. Species composition shifted away from small colonists (principally cyprinids and small centrarchids) toward larger centrarchids, catostomids, and ictalurids. Major gains in stream ecosystem rehabilitation can be made through relatively modest but well designed efforts to modify degraded physical habitats.