Hammersmark, C. T. (2008). Assessing the Hydroecological Effects of Stream Restoration. Hydrologic Sciences. Doctor of Philosophy.
This dissertation consists of three studies undertaken to document and quantify the hydroecological effects of stream restoration. The study was conducted at the Bear Creek Meadow, a particularly well-documented “pond and plug” type stream restoration project, located in northeastern California.
The first study investigates the effects of stream restoration on hydrologic processes. A hydrologic model of the 230 ha meadow was developed, calibrated, validated, and used to simulate the system under pre- and post-restoration topographic conditions. Simulation results document three general hydrologic responses to the meadow restoration effort: 1) increased groundwater levels and volume of subsurface storage; 2) increased frequency and duration of floodplain inundation and decreased magnitude of flood peaks; and 3) decreased annual runoff and duration of baseflow.
The second study explores the relationship between temporally varying water-table elevations and plant community distributions in the restored riparian meadow. Vegetation was sampled throughout the meadow and TWINSPAN was used to classify the vegetation into four community types: Eleocharis macrostachya / Eleocharis acicularis, Downingia bacigalupii / Psilocarphus brevissimus, Carex nebrascensis / Juncus balticus, and Poa pratensis / Bromus japonicus. The hydrologic model was used to simulate a three-year time series of water-table depth for each plot, and nonmetric multidimensional scaling was utilized to investigate the relationships between community types and hydrologic variables. Community types were distributed along the hydrologic gradient at reasonably similar positions to those found in previous studies, however the range of water-table depths in this meadow was greater than previously observed, presumably due to the higher temporal resolution of water-table measurements, in addition to the intermittent nature of stream flow in Bear Creek and its substantial control of water-table elevations.