Culverts and bridges are necessary in order to cross waterways during road construction. However, these structures have detrimental affects on the hydrology and ecology of the streams they cross. The objective of this study was to investigate how these bridges and culverts alter stream hydrology and geomorphology by determining the effects on the upstream and downstream reaches of a road crossing on the cross sectional area, the hyporheic depth, on riffle habitat, and substrate types. Three types of culverts (arch, box, and pipe) and small bridges were evaluated. All four types of stream crossings were determined to increase the cross sectional area downstream of the structure. Crossing structures also affected hyporheic zone depths by decreasing average depths downstream of the structure. Finally, most mussels seemed to occur in substrates that were dominated by relatively large particles (gravel and cobble) that were less movable by sheer stress during higher flows. Each of the problems discovered with these structures is a result of the channel restriction and the increased flow velocity and turbulence scour that it creates. These detrimental conditions can be mitigated by providing for floodplain access for higher flows. It is recommended that culverts be designed for low flows and high flows. Oversizing culverts, compared to current design criteria will allow floodplain access and build bankfull benches in the extra openings to restrict low flows to a few openings. The use of bridges that span across the valley limiting fill and allowing floodplain access may even be more beneficial. When valley fill is necessary, then side culverts in the floodplain may alleviate degradation and allow more natural floodplain hydrology.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-11302005-175258 |
| Date | 07 December 2005 |
| Creators | Merrill, MaximilIan Atlas |
| Contributors | Dr Samuel Mozley, Dr James Gregory, Dr Garry Grabow |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-11302005-175258/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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