East Branch Pecatonica River
Hydroecological Effects of Restoration
We are interested in quantifying the changes in floodplain hydrology and vegetation in response to restoration. Because floodplains represent the nexus between terrestrial and aquatic ecosystems, the fluxes of water within and at the boundaries of the floodplain are highly varied in both space and time and play a dominant role in driving ecosystem processes. These hydrologic fluxes include:
Groundwater flow including seepage faces
Several predictions of the effect of restoration include:
decrease in the depth to water table
increase in evapotranspiration
increase in wetland vegetation
Each hydrologic flux shown above will be monitored in the field and modeled in order to test hypotheses and different management scenarios at two different sites owned by TNC. The first site is the floodplain that was restored in 2006 (above figure on right) and the second site is a slightly smaller floodplain located approximately 1.7 km upstream of the 2006 restoration site. This second site was restored in early September 2008 (above figure on left shown before restoration). Because monitoring of the two sites began in the spring of 2007, our strategy is the collection of pre- and post-restoration data at the 2008 site to offer a comparison, while using the 2006 site as a space-for-time substitution in that it may represent conditions at the 2008 site two years in the future.
Riparian vegetation will be monitored at the community-level using ground-based vegetation surveys and remote sensing data collected from a small plane. The remote sensing equipment includes a thermal, 6-band near-infrared, and standard SLR camera.
Vegetation maps will be combined with simulated hydrologic data using a variably-saturated groundwater flow model to generate a dataset of combined hydrologic regime statistics and vegetation observations. Using this spatially-extensive dataset, non-linear vegetation models will be generated based on the hydrologic regime metrics (based on water-table depth and soil moisture) that best explain the occurrence of each vegetation community. For example, the occurrence of a wet-prairie community may be well explained by the median water table depth during the growing season.
These community-specific vegetation models will then be coupled to the variably-saturated groundwater flow model to create a hydroecologic model that will give spatially-extensive predictions of vegetation. Different management or climate scenarios could then be tested to determine impacts on vegetation patterning.
In addition to floodplain hydrology and vegetation, we will also be quantifying the changes in channel geometry and subsequent changes in flood hydraulics. Since the restoration process re-connects the channel with its floodplain during high flows, we predict that stream velocity and depth will decrease and width will increase for a given flood discharge.