Hootsmans, James Antony Stewart (2015-08). River Restoration of the Upper Reach of the San Miguel River, Colorado: A Post Appraisal Geomorphological Analysis. Master's Thesis.
Thesis
The upper reach of the San Miguel River has undergone river restoration in a two-phase approach. The first phase was carried out in 2001; the second phase was completed in 2004. Although detailed plans were developed for the restoration of part of the river, only short-term (i.e., three year) monitoring occurred. Thus, one can ask: was river restoration on this part of the San Miguel River effective after ten years? For the purpose of this research, if the river channel and its meanders maintained the relative geometries, then the restoration is considered effective. To assess the effectiveness of the restoration, a one-km section of the San Miguel River in Telluride, Colorado, was studied. This section begins ~ 150 m above the confluence of the river with Bear Creek on the eastern side of Telluride and ends at the Mahoney Street Bridge on the western side. To answer the research question, changes in the channel width, meander location, and sinuosity were determined using a series of Google Earth(R) images, measured cross-sections at twenty-two sites and high-resolution video collected with an Unmanned Aerial Vehicle. In addition, published hydrological, ecological and geomorphological data collected by the State of Colorado, the USGS, NOAA and the Town of Telluride were used. These data include rates of sedimentation and discharge, weather patterns, aquatic biomass and vegetation presence, changes in land use, and alterations to the channel. The bank-to-bank width averaged ~10.2 -10.5 m in 2014, and depth ranged from 0.2 to 1 m, resulting in width/depth (W/D) ratios of >10. Sinuosity remained consistent at 1.16 during the period 1998 - 2014. Sediment continued to be deposited in the channel during the ten-year period despite the construction of a sediment retention basin at the start of the project. As a result of high volume of sediment, the Town of Telluride excavated the sediment retention pond yearly from 2001 to August 2014. Approximately, 500 m3 of sediment was removed annually. Hydrologically, no significant difference in mean discharge occurred from 1992-2014. Water chemistry parameters including nitrate, conductivity and dissolved oxygen were consistent between the upstream and the downstream sections. Dissolved oxygen concentrations were within the water quality limit of 6 mg/L (Class 1 Cold Water Biota). Conductivity levels increased consistently from 2004 - 2012, above the limit of 0.500 mS/cm for "good quality inland waters", as defined by national standards. By August 2014, the conductivity had returned to historical levels of 0.35 mS/cm. Total trout biomass roughly doubled from 22 to 44 kg/ha. Despite channel movement and sediment deposition, the restoration was considered effective.
The upper reach of the San Miguel River has undergone river restoration in a two-phase approach. The first phase was carried out in 2001; the second phase was completed in 2004. Although detailed plans were developed for the restoration of part of the river, only short-term (i.e., three year) monitoring occurred. Thus, one can ask: was river restoration on this part of the San Miguel River effective after ten years? For the purpose of this research, if the river channel and its meanders maintained the relative geometries, then the restoration is considered effective. To assess the effectiveness of the restoration, a one-km section of the San Miguel River in Telluride, Colorado, was studied. This section begins ~ 150 m above the confluence of the river with Bear Creek on the eastern side of Telluride and ends at the Mahoney Street Bridge on the western side.
To answer the research question, changes in the channel width, meander location, and sinuosity were determined using a series of Google Earth(R) images, measured cross-sections at twenty-two sites and high-resolution video collected with an Unmanned Aerial Vehicle. In addition, published hydrological, ecological and geomorphological data collected by the State of Colorado, the USGS, NOAA and the Town of Telluride were used. These data include rates of sedimentation and discharge, weather patterns, aquatic biomass and vegetation presence, changes in land use, and alterations to the channel.
The bank-to-bank width averaged ~10.2 -10.5 m in 2014, and depth ranged from 0.2 to 1 m, resulting in width/depth (W/D) ratios of >10. Sinuosity remained consistent at 1.16 during the period 1998 - 2014. Sediment continued to be deposited in the channel during the ten-year period despite the construction of a sediment retention basin at the start of the project. As a result of high volume of sediment, the Town of Telluride excavated the sediment retention pond yearly from 2001 to August 2014. Approximately, 500 m3 of sediment was removed annually. Hydrologically, no significant difference in mean discharge occurred from 1992-2014.
Water chemistry parameters including nitrate, conductivity and dissolved oxygen were consistent between the upstream and the downstream sections. Dissolved oxygen concentrations were within the water quality limit of 6 mg/L (Class 1 Cold Water Biota). Conductivity levels increased consistently from 2004 - 2012, above the limit of 0.500 mS/cm for "good quality inland waters", as defined by national standards. By August 2014, the conductivity had returned to historical levels of 0.35 mS/cm. Total trout biomass roughly doubled from 22 to 44 kg/ha. Despite channel movement and sediment deposition, the restoration was considered effective.
