Fish Passage in Urban Streams Poster: Using River Continuum Concepts in Site Selection

Abstract

This paper presents the concepts and applications used to locate the fish passage improvements along Northwest Branch in Prince George’s County, Maryland. These structures are required as part of the environmental mitigation package for the Woodrow Wilson Bridge Project. The authors proposed the installation o f riffle grade control structures (RGCs) to improve fish passage at seven blockages along Northwest Branch. Since RGCs are not common fish passage structures, the design methodologies have not been widely documented and standardized. The intent of this paper is to demonstrate how these proposed RGCs were located in the existing channel system based on field indicators. CONSTRUCTED RIFFLE GRADE CONTROLS Projects reviewed as part of the Northwest Branch design were the Sacramento River Gradient Restoration Facility (Hogan 2000) and the Marble Bluff Dam Flood Repair Project on the Truckee River, both of which were field inspected by an author (Hegberg) in October 2000. These structures were reviewed, because fish passage was a significant component of their design, and the fish passage capabilities were modeled extensively. Both of these sites differed significantly from Northwest Branch in channel size, targeted fish species, hydrology and hydraulics. In addition, both of these sites are single site applicatio ns that did not take into account reach length scales. However, significant lessons were learned from the computer modeling efforts and construction experience. In Baltimore County, Maryland, RGC structures were used to stabilized two reaches of White Marsh Run. Six RGCs were constructed along these reaches to stabilize this high bed load stream. Although these structures were not designed for fish passage, spring flow depth and velocity measurements on these RGCs indicate that they would promote fish passa ge. Figure 1 presents a photograph of a RGC in White Marsh Run in White Marsh, Maryland. The White Marsh Run RGCs are unique in that they were installed in series with intermediate pools, whereas most constructed riffles are installed as isolated structure s. The successes of these RGCs provide the technical foundation for designing and locating a series of RGCs along two long reaches of Northwest Branch.