An attempt was made to mitigate the impact of highway construction on a wetland (beaver pond) margin by enhancing the shoreline of the roadfill. One hundred 20-ft-long fingerlike extensions 10 ft widewere constructed 10 ft apart along the roadfill. The extensions increased the pond-roadfill margin by a factor of three. Willows were planted on the southeastern edge of the fingers. Despite repeated draining of the pond by county surveyors and two successive drought years, the procedure appeared successful. Transects were compared in three areas: an improved section with fingers; an unimproved section of roadfill; and a "control" across the pond from the roadfill. Sampling of the pond margin communities over a 3-year period revealed up to 89% the number of benthic invertebrates in the improved area as in the control and only 44% of the benthos in the unimproved area as in the control area. Trees occurred on the fingers at a rate 2.3 Times greater per unit of shoreline than in the unimproved area, and over half were volunteers. Fish used the improved area about four times as much as the unimproved area. A community coparison index showed the shoreline tree community in the improved area to have about six times the habitat value of the unimproved area. Recommended modifications of the shoreline include making the fingers longer and widerand the sloughs wider and deeper, and providing erosion control andless slope to prevent excessive sedimentation. This paper appears in transportation research record no. 1224, Rest areas, wetlands, andhydrology.
Abstract