Should Fish Passage through Culverts be a Concern for Midwest Engineers and Planners: Determining the Percentage of Culverts that act as Barriers to Fish Passage in NE Ohio

摘要

While most fish passage analysis, retrofit, and design have been focused on imperiled anadromous species in states along the coasts, in Midwest watersheds such analysis has not historically been viewed as a primary concern to regional water policy. This is due, in part, to the assumption that there is not a migration (or connectivity) problem since there are not any large migratory keystone species. However, it's anticipated that a significant fraction of Midwest culverts cause impacts to fish movement, and the goal of this research is to determine the percentage of culverts that are barriers to fish passage in this region. To assess the passage rates of native fish species in existing Midwest culverts, the research team used regional databases, GIS tools, and two fish passage analysis programs to determine the percentage of culverts in Northeast Ohio that are barriers to fish migration. Ohio Department of Transportation supplied a database of existing highway culverts containing 5,837 culverts; it was determined that 169 culverts had enough information (material, slope, diameter, shape), sufficient diameter (>24 inches), a discernible channel geometry, and circular shape (simplified analysis for this first assessment) to predict fish passage success rates. At present results of 55 culverts have been analyzed using FishXing and one culvert using an add-on HEC-RAS code that predicts fish passage. Results from the analysis using FishXing indicate that none of the selected fish species was able to pass upstream through any of the culverts during the 2 year flood, two of the fish (Greenside darter and Golden shiner) were able to pass on average 3% of the culverts during highest average monthly flow, two of fish species (Greenside darter and Blacknose dace) were able to pass on average 25% of the culverts during the minimum average monthly flow, and on average 13% of the culverts during the typical low flow day (25% low flow). Results obtained with the HEC-RAS tool showed only moderately better passage conditions, with the main cause for the barrier being excessive velocity, in spite of the streams' moderate hydraulic gradients. While additional analysis of the remaining culverts is necessary, both the method outlined and the results are expected to be useful in aiding fish passage analysis and design.