Study of bankfull culvert design effectiveness

Performing organization: Cleveland State University, Dept. of Civil & Environmental Engineering.; "Prepared in cooperation with the Ohio Department of Transportation and the U.S. Department of transportation, Federal Highway Administration."; "June 2011."; Leaves of Appendix A folded.; Accompanying CD-ROM contains appendices A-E (PDF files) and appendix F (photos).; "FHWA/OH-2011/12"--Technical rept. documentation p.; Includes bibliographical references (p. 54-58).; "For the Ohio Department of Transportation, Office of Research and Development, State Job Number 134465."; Harvested from the web on 7/8/11As part of the certification under the Clean Water Act 404 Nationwide Permit, the Ohio EPA mandated that the Ohio DOT install bankfull culverts in all new culvert installations subject to the permit. In addition, by embedding the culvert, the bottom of the culvert is to take on the characteristics of the natural streambed and promote the passage of fish and other aquatic organisms. The OEPA's requirement to install bankfull culverts has resulted in increased design and construction costs. The objectives of the study were to examine the parameters which control the benefits of bankfull culverts when installed, including how the benefits alleged are affected by culvert diameter, slope and length, and the size of the stream in which the culvert is placed. Ultimately, the research was designed to determine if bankfull culverts, as currently installed, provide the benefit of allowing movement of aquatic biota better than traditional culverts, if there is any impact on flood attenuation, and if the bankfull culverts installed in Ohio have caused quantitative environmental changes or cumulative impacts (as measured by the QHEI). The physical survey of the culverts revealed that of the 61 culverts identified by ODOT as being designed as embedded bankfull culverts (EBCs), there are only 12 that are actually embedded. ODOT should develop and implement a system of inspecting and verifying that culverts specified to be embedded bankfull culverts are actually installed as such. An important finding is that many of the culverts with greater than 1% slope had no sediment present inside of the culvert. The results of the survey indicate that, at the 90% confidence interval, sediments are being washed through culverts with a slope 1% or greater. Therefore it is recommended that EBCs should not be installed at slopes greater than 1%. Of the 12 embedded culverts, only two were found to be effectively allowing for the continuity of sedimentation patterns through the reach of a culvert. Because of the low numbers, the results found are not statistically significant. To better understand the functionality of culverts and the trends presented, more research is needed. ODOT should consider funding additional research in this area to confirm preliminary trends and provide more guidance in the design of embedded bankfull culverts