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Using monitoring, LiDAR and MODFLOW to Estimate Hyporheic Fluxes for a Dynamic Large River Riparian Area
Citation:
FAULKNER, B. R. Using monitoring, LiDAR and MODFLOW to Estimate Hyporheic Fluxes for a Dynamic Large River Riparian Area. In Proceedings, MODFLOW and More 2011 Conference, Golden, CO, June 05 - 08, 2011. International Ground Water Modeling Center, Golden, CO, 415-419, (2011).
Impact/Purpose:
Poster for the proceedings of the MODFLOW and More 2011 Conference
Description:
In unrevetted reaches, the Willamette River in northwest Oregon is a dynamic anastomosing system. Riparian zones are frequently divided into multiple islands during most of the wet winter season. The dividing stream channels are mostly absent during the dry summer season. This poses challenges for developing ground water flow models which incorporate river stage and the changing channel positions. This application of MODFLOW relies heavily on monitoring and LiDAR data collected from recent flights for the Willamette Valley for estimating both river stage and elevation. Steady-state models for both the wet and dry seasons were developed and they show dramatically differing hyporheic flow nets. During the dry season, hyporheic flow pathlines are deep and tend to orient parallel to the slope of the floodplain. Flow speeds are mostly less than 5 cm per day. During the wet season, hyporheic pathlines are much shallower, and driven laterally from the main river through islands to rapidly seep into cutoffs and alcoves. Flow speeds are on the order of one to two meters per day. Revetment removal is being considered in some areas of the Willamette Valley as a means of recovering the natural river riparian zone geomorphology. Since hyporheic flow is linked to beneficial ecosystem services, such as nutrient attenuation and salmon habitat cooling, the flow patterns revealed in these modeling results have implications for revetment removal as a restoration practice.
