Analyzing post-flood recovery after an extreme flood: North St. Vrain Creek, CO
| dc.contributor.author | Eidmann, Johanna S., author | |
| dc.contributor.author | Rathburn, Sara, advisor | |
| dc.contributor.author | Wohl, Ellen, committee member | |
| dc.contributor.author | Nelson, Peter, committee member | |
| dc.date.accessioned | 2018-09-10T20:04:59Z | |
| dc.date.available | 2018-09-10T20:04:59Z | |
| dc.date.issued | 2018 | |
| dc.description.abstract | Assessing the ongoing sediment remobilization and deposition following an extreme flood is important for understanding disturbance response and recovery, and for addressing the challenges to water resource management. From September 9-15, 2013, a tropical storm generated over 350 mm of precipitation across the Colorado Front Range. The resulting 200-year flood triggered landslides and extreme channel erosion along North St. Vrain Creek, which feeds Ralph Price Reservoir, water supply for the Cities of Lyons and Longmont, CO. The flood resulted in 10 m of aggradation upstream of the reservoir, transforming the reservoir inlet into an approach channel. 4 years after the flood, downstream transport of flood sediment and deposition in the reservoir continues. This research tracks the fate of flood-derived sediment to understand the evolution of the approach channel and delta to assess post-flood response processes and controls and to quantify sediment remobilization. Photographic analysis and DEM differencing of the approach channel indicates that the majority of channel response to the flood occurred within 1 year following the flood. Evolution of the channel from an initial plane bed occurred through channel incision of up to 2.5 m and widening of up to 10 m, forming a trapezoidal cross section. Channel geometry changes in years 2-5 post-flood are limited in spatial extent, largely dependent on sediment discharge and local variations in channel confinement. Bathymetric DEM differencing from 2014 and 2016 (years 1 and 3 post-flood) indicates a minimum sediment accumulation of 68,000 m3 on the delta plain, and progradation of 170 m of the delta front since the 2013 flood. Between fall 2016 and spring 2017, the reservoir level was dropped approximately 10 m during construction at the spillway, creating a base level drop, delta incision, and causing over 15,000 m3 of sediment to be transported further into the reservoir. Based on bathymetry and reservoir core analyses, a total of 74,000 m3 of sediment was deposited in the delta from 2014 through 2017, producing an estimated loss of 0.4% in reservoir storage capacity. Approximately 184,000 m3 (equivalent to another 1% of reservoir storage capacity) is estimated to remain in storage upstream of the reservoir. Although the approach channel appears to be adjusted to a typical snowmelt runoff, stored sediment remaining upstream of the reservoir indicates that complete recovery of the approach channel may not occur on a management time scale. The remaining large volume of sediment still in storage upstream highlights the potential for future disturbances to trigger additional sediment inputs. | |
| dc.format.medium | born digital | |
| dc.format.medium | masters theses | |
| dc.identifier | Eidmann_colostate_0053N_14981.pdf | |
| dc.identifier.uri | https://hdl.handle.net/10217/191391 | |
| 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.title | Analyzing post-flood recovery after an extreme flood: North St. Vrain Creek, CO | |
| 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 | Geosciences | |
| thesis.degree.grantor | Colorado State University | |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.S.) |
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