Increased sedimentation caused by post-fire flooding is a risk to people, homes, and buildings. The USDA Forest Service installs straw bale check dams in ephemeral channels to reduce sedimentation rates from small catchments. We set out to study if straw bale check dams effectively reduce sedimentation rates from five paired catchments following the 2010 Twitchell Canyon Fire in south central Utah. Each pair consisted of two adjacent catchments that had similar physical characteristics and areas, with catchment areas ranging from ~0.2 to 1.6 ha (~0.5 to 4.0 ac). For each pair we treated one catchment with four straw bale check dams per ha (two per ac) and left the other catchment untreated as a control. Sediment yields produced from catchments during 2011 and 2012 were measured as well as the mass of sediment trapped by individual straw bale check dam structures. We found straw bale check dams did not significantly reduce annual catchment sediment yields produced by 30-minute rainfall intensities (I30) equal to or less than 14 mm hr-1 (0.5 in hr-1), a 1-year return period event at the study area. The straw bale check dams were filled to sediment holding capacity early in the first post-fire year from sediment yields produced by 1- and 2-year I30 return period rain events, or by two rain events having less than 1-year I30 intensity return periods. Three of the five paired catchments did not capture the total 2011 annual sediment yields because sediment retention structures used to measure catchment yields were overwhelmed by sediment during large rain events, however reliable measurements indicate annual sediment yields of 19.53 to 25.71 Mg ha-1 [8.71 to 11.47 t ac-1] passed over already full straw bale check dams. Straw bale check dams were non-functioning during the second post-fire year, allowing 3.74 to 13.12 Mg ha-1 [1.67 to 5.85 t ac-1] of sediment to pass over structures. The mean mass of sediment trapped by individual straw bale check dams is 1.26 Mg (1.40 t). At a treatment rate of four straw bale check dams ha-1 (two ac-1), they trapped 5.87 Mg ha-1 (2.62 t ac-1) of sediment.
| Identifer | oai:union.ndltd.org:MONTANA/oai:etd.lib.umt.edu:etd-06192013-113457 |
| Date | 28 June 2013 |
| Creators | Storrar, Keenan |
| Contributors | Peter R. Robichaud, Mike Patterson, Cara Nelson, Andrew Wilcox |
| Publisher | The University of Montana |
| Source Sets | University of Montana Missoula |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.umt.edu/theses/available/etd-06192013-113457/ |
| 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 University of Montana 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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