Helen Dahlke

Email:  hed23@cornell.edu
Phone: 607-255-0185
Office: 165 Riley Robb Hall
Advisor: Tammo Steenhuis
Degree Program: Ph.D. cand.

Background

I have studied at the Friedrich-Schiller University in Jena, Germany and graduated with a diploma in Geography and minors in Geology and Ecology. My diploma thesis focused on the terrain-based delineation of wetlands in South Africa using GIS.

Current Research Interests

Hillslope Hydrology, hydrological process research, variable source area (VSA) hydrology, landscape analysis, GIS & Applied Geophysics, vegetation analysis.

Research on VSA Hydrology

In my reasearch I look at hydrological processes of variable source areas (VSA). On two hillslopes I study subsurface flow pathways, groundwater table dynamics and spatio-temporal dynamics of VSAs in relation to soil and landscape characteristics. Main emphasis is especially put on the application of Ground Penetrating Radar (GPR) for the characterisation of soil properties and the localization of fragipans.

Development of a web tool to forecast spatially distributed runoff dynamics

Beside my research I am working on the development of an online-accessible Tool that is displaying the extent and dynamics of areas prone to generate runoff, also called hydrological sensitive areas (HSA), in the Salmon Creek watershed. The surface runoff potential is calculated on a daily basis using a water balance model (Thornthwaite-Mather) and free precipitation and temperature data from the National Climatic Data Center and is distributed via a soil topographic index to capture VSA dynamics. The tool is designed to interactively assist planners and especially farmers in the BMP planning process. It can be used to locate fields with low runoff risk that could, potentially receive more liberal nutrient applications without increasing the risk of NPS pollution. In addition data such as the soil drainage properties or the flood frequency of soils are provided to assist farmers in applying the Phosphorus Index for Best Manegement Practices planning. The VSA Tool for Salmon Creek .

Publications

Dahlke, H.E., Easton, Z.M., Fuka, D.R., Lyon, S.W. and, T. S. Steenhuis. 2009. Modeling Variable Source Area Dynamics in a CEAP Watershed. Ecohydrology (in print).

Dahlke, H.E., Behrens, T., Seibert, J., and L. Andersson. 2008. Test of statistical means for the extrapolation of soil depth point information using overlays of spatial environmental data and bootstrapping techniques. Hydrological Processes (submitted).

Archibald, J.A., Buchanan, B., Dahlke, H.E., Easton, Z.M., Marjerison, R.D., Sharma, A.N., Shaw, S.B. and M.T. Walter. 2008. A new paradigm for sizing riparian buffers to reduce risks of polluted storm water: A practical synthesis. ASCE J. of Irrigation and Drainage Engineering (submitted).

Dahlke, H.E., Easton, Z.M., Fuka, D.R., Rao, N.S., White, E.W., Veith, T., Schneiderman, E.M. and T S. Steenhuis. 2008. An interactive web tool to forecast spatially distributed runoff dynamics. Proceeding of the Conference of the 50th Anniversary of the National Sedimentation Laboratory, Oxford, MS, 03.-05. Sept. 2008.

de Alwis, D.A., Easton, Z. M., Dahlke, H.E., Philpot, W. D. and T. S. Steenhuis. 2007. Unsupervised classification of saturated areas using a time series of remotely sensed images. Hydrol. Earth Syst. Sci., 11, 1609-1620, 2007.full text

Helmschrot, J., Dahlke, H.E. 2006. Inventory and Monitoring of South African Wetlands Integrating Field Data, Earth Observation Data Analysis, and GIS-based Terrain Analysis. Globwetland Symposium 'Looking at wetlands from space', 19./20. October 2006, Frascati, Italy.