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Sitka Sedge State Natural Area Hydrology Modeling

Oregon Parks and Recreation Department (OPRD) has contracted Pacific Groundwater Group (PGG) and Environmental Science Associates (ESA) to perform a comprehensive hydrological analysis of potential interactions between tidal surface water inside the Beltz Dike and groundwater levels in the neighboring town of Tierra del Mar, Oregon.  This work will build on initial hydrological modeling, groundwater analysis, and data collection from previous years. Outcomes of detailed modeling and analysis will inform future decisions for habitat restoration on OPRD property, especially regarding potential effects on groundwater that might result from increased tidal exchange in the estuary.

As of February 2018, a series of groundwater monitoring wells have been installed along with surface water monitoring stilling wells in key locations. Data collection is scheduled to continue for at least six weeks, and will continue until at least one major storm event is captured so that the hydrological characterizations include a representative range of groundwater conditions. After data collection is complete, PGG and ESA will proceed to creating a conceptual model of existing hydrological conditions, and then to creation of predictive models that can incorporate different tidal scenarios. There will be two in-person stakeholder meetings in 2018.  The first meeting will present results of existing conditions conceptual model development, present proposed methods for performing predictive groundwater modeling, and allow stakeholders to provide input and help guide methodology for further predictive modeling.  The first step in predictive modeling will be to find the thresholds of surface water inundation of the marsh at which groundwater effects would be expected in Tierra del Mar and to identify suitable parameters for estimation of sea level rise and climate change. The second meeting will present results of initial predictive modeling and thresholds for groundwater effects, and will focus on identification of potential further refinements and scenarios to be assessed by the predictive models.  PGG/ESA will then assess all of the identified scenarios and produce a final report detailing the predicted effects of each of the scenarios tested.

Sitka Sedge Hydrological Analysis Statement of Work (10/2017)

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