Sediment production and delivery from hillslopes and forest roads in the southern Sierra Nevada, California
| dc.contributor.author | Stafford, Allison K., author | |
| dc.contributor.author | MacDonald, Lee H., advisor | |
| dc.contributor.author | Stednick, John D., committee member | |
| dc.contributor.author | Butters, Gregory, committee member | |
| dc.date.accessioned | 2007-01-03T05:16:27Z | |
| dc.date.available | 2007-01-03T05:16:27Z | |
| dc.date.issued | 2011 | |
| dc.description.abstract | Unpaved roads often are a major source of sediment to streams in forested watersheds, and an increase in sediment production and delivery can adversely affect the overall health of a stream. The goals of this study were to first quantify the effects of climate and soil type on hillslope and road sediment production and delivery, and then evaluate the effects of graveling, grading, and waterbar construction on road sediment production and delivery. Sediment fences were used to collect 109 fence-years of data from water years 2008 and 2009 in the more rain dominated José Basin (800-1200 m) and 193 fence-years of data in the snow dominated Kings River Experimental Watersheds (KREW) (1485-2420 m), both located in Sierra National Forest (SNF) in California. Detailed road surveys assessed road segment characteristics and road-stream connectivity. Mean hillslope sediment production in José Basin was 3.7 x 10-3 kg m-2 yr-1, which was similar to the value of 4.1 x 10-3 kg m-2 yr-1 in KREW. Native surface road segments in José Basin had a mean sediment production rate of 1.8 kg m-2 yr-1, and the estimated total sediment production from the 67 km of native surface roads is 680 metric tons per year. An estimated 30% of the native surface road length is connected to the stream network, indicating that up to 210 metric tons of sediment may be delivered to streams each year. There was no significant difference in sediment production and delivery between road segments in the highly erodible Holland soil and road segments in other soil types. Mean sediment production for the native surface road segments in the KREW watersheds was 0.13 kg m-2 yr-1, which was more than an order of magnitude lower than the mean value in José Basin, and road-stream connectivity was only 3%. There was no significant difference in sediment production from native and gravel surface road segments in José Basin due to the high variability and the gravel segments still averaged 51% bare soil. The gravel surface segments had shorter drainage features than native surface segments, but 40% of the gravel roads were connected as they tended to be closer to streams. Graveled roads in the Providence Creek watersheds produced 0.16 kg m-2 yr-1, which was only 22% as much sediment as the native surface roads, and had 11% connectivity. In José Basin grading initially decreased the mean segment length from 65 m to 41 m, but one year after grading 22% of the waterbars had failed, leading to a 15% increase in mean segment length. Graded road segments in José Basin produced eight and three times more sediment per unit area than ungraded segments in WY2008 and WY2009, respectively, and this can be attributed to extensive rilling. Sediment production rates decreased by 40-60% from the first to the second year after grading. Sediment production and delivery from forest roads can be reduced by: 1) using more than 30% gravel cover on native surface roads, 2) minimizing grading, and 3) improving the construction of waterbars to better withstand and direct overland flow. | |
| dc.format.medium | born digital | |
| dc.format.medium | masters theses | |
| dc.identifier | Stafford_colostate_0053N_10420.pdf | |
| dc.identifier.uri | http://hdl.handle.net/10217/47458 | |
| dc.language | English | |
| dc.language.iso | eng | |
| dc.publisher | Colorado State University. Libraries | |
| dc.relation.ispartof | 2000-2019 | |
| dc.rights | Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright. | |
| dc.subject | erosion | |
| dc.subject | sediment | |
| dc.subject | road | |
| dc.title | Sediment production and delivery from hillslopes and forest roads in the southern Sierra Nevada, California | |
| dc.type | Text | |
| dcterms.rights.dpla | This Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). | |
| thesis.degree.discipline | Forest, Rangeland, and Watershed Stewardship | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.S.) |
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