The model is fully three-dimensional and includes the lateral hyporheic zone in addition to the flow directly beneath the streambed. The primary model input parameters are stream velocity and slope, sediment permeability and porosity, and detailed measurements of the stream channel topography. The primary outputs are the distribution of water flux across the stream channel boundary, the resulting pore water flow paths, and the subsurface residence time distribution. I validated the bedform-exchange component of the model using a highly detailed two-dimensional dataset for exchange with ripples and dunes, and have applied the model to multiple three-dimensional datasets. A Schwarz-Christoffel conformal mapping procedure was used to align the topography with the flow direction in order to more accurately calculate the boundary head distribution over submerged topographic features in meandering channels. Lateral (floodplain) exchange was simulated using a finite-difference solution based on the in-stream head values and flume boundary conditions. The surface-subsurface boundary conditions are calculated by Fourier fitting the topography, shifting each term by a quarter of a wavelength, and piecewise scaling the resulting function based on local conditions. Groundwater discharge is simulated by raising head levels on the longitudinal boundaries.

The first part of this video shows 2D topography data being fit by sine curves. The second part shows each of these sine curves being shifted by a quarter wavelength to produce the head shape.


    Since then, my principle involvement has been in collaboration with USGS staff at sites in Indiana, Nebraska, and North Carolina. We performed solute tracer experiments and measured flow rates, sediment properties, and the system's bathymetry at each site. Data collection techniques at each site varied based on the system. In Indiana the stream was small, straight, and ditched. The elevation of the banks allowed for pictures to be taken, which could be pieced together into a detailed map of the system. This was a great advantage for locating measurements and provided a detailed outline of the stream. In Nebraska we hired a team to perform LIDAR of our reach, which provided a partial map along with detailed topography measurements. In North Carolina the stream came equipped with its own dam, with which we stopped much of the water flow and then released it, simulating a large flow event.

    These collaborative experiences have allowed me to meet interesting people, learn experimental techniques, and expand my perspective of environmental research. This type of research has also given me the opportunity to supervise undergraduates in a variety of field work settings.

Making measurements in Sugar Creek near Kentland, IN

Set-up for measuring fine topography

    Laboratory flumes allow individual conditions like slope, water depth, velocity, and sediment type to be adjusted, aiding in the identification of trends and theory formulation. While laboratory settings cannot replicate the full extent of conditions found in natural systems, the additional control makes them a valuable tool for the study of solute transport. My work in laboratory flumes has allowed me to verify several principles of hyporheic exchange and to demonstrate research topics to a variety of audiences.

Bedforms and dye in a laboratory flume