A 2-D, DIFFUSION-BASED, WETLAND FLOW MODEL

Surface water flow in wetlands occurs typically in a low gradient envi ronment where topographic and flow resistance variations control the d ischarge distribution. it is within this fluid mechanical regime that the biochemical processes constituting wetland ecology take place. Pre sented herein are the basics of a mathematical model that takes advant age of the hydraulics typical of wetlands. The resulting model, in the form of a 2-D, non-linear diffusion equation, allows incorporation of spatial variations in Bow resistance and topography, The applicabilit y of the model to one- and two-dimensional wetland type flow is demons trated using two cases: a laboratory experiment and a wetland pond. Re sults illustrate the versatility of the formulation and the important influence of topography variations on flow depth and velocity variatio ns. The use of a fixed rectangular calculation domain to simulate the flow pattern in wetlands with irregular wet boundaries is the most sig nificant practical aspect of the WETFLOW model. Future research will c oncentrate on dealing with extreme heterogeneity in the elevation and Bow resistance distributions, through a combination of measurements an d use of stochastic fractals to represent property distributions (Molt and Boman, 1993, Water Resour. Res., 29: 3769-3774). Experimental stu dies are needed to quantify the relationship of Bow resistance to diff erent combinations of slope, water depth, and a suitable measure of ve getation density for a wetland ecosystem. (C) 1997 Elsevier Science B. V.