Hydrogeomorphic Model Research Articles

Embedding landscape processes into triangulated terrain models

Triangulated irregular networks (TIN) can form the basis for multiple‐resolution representations in distributed hydrogeomorphic simulations over complex basins. Current methods for deriving TIN meshes depend primarily on surface slope without considering other terrain attributes significant to the watershed response such as the specific basin area. As an alternative, we present a methodology for combining a hydrogeomorphic or landscape index with an unstructured triangulated mesh. Landscape indices provide a concise method for describing steady‐state terrain processes by isolating the dominant physical factors. The mesh‐generation algorithm results in an adaptive discretization that resembles the spatial pattern of the landscape index with a high resolution retained in areas expected to impact the basin response. We compare the proposed algorithm with a slope‐preserving method as a means for initializing the terrain representation in two TIN‐based hydrogeomorphic models. Through three case studies in saturation‐excess runoff, transport‐limited soil erosion and shallow landslide simulation, we assess the distributed model sensitivity to the triangulated terrain algorithm. Model comparisons reveal that the process‐based triangulations focus the distributed simulation in regions anticipated via a steady‐state index to affect the transient watershed response.

Plant Community Patterns of Low-Gradient Forested Floodplains in a New Jersey Urban Landscape

ARONSON, M. E J., C. A. HATFIELD, AND J. M. HARTMAN. (Graduate Program in Ecology and Evolution, Rutgers University, New Brunswick, NJ 08901-1582). Plant community patterns of low-gradient forested floodplains in a New Jersey urban landscape. J. Torrey Bot. Soc. 131: 232-242. 2004.-This study characterized the vegetation of floodplain forests along a 66 km stretch of the upper Passaic River in northern New Jersey, USA. Although the study wetlands lie in a highly disturbed region of New Jersey, they are intact and well-buffered floodplains. A characterization of wetlands in this region is imperative to properly assess and restore natural lands in this ever increasingly developed landscape. As in similar floodplain systems, there was a change in canopy composition along the 66 km stretch. Specifically, Quercus palustris dominated forests shifted to Acer saccharinum dominated forests near the midpoint of the sampled river section. Sub-canopy, shrub and ground vegetation were sampled but clear patterns were not detected with respect to position along the sampled river section. Species richness was lower than any other published descriptions for this type of floodplain system. The low species richness in all strata may be attributed to urban influences although this requires additional study. Exotic flora represented up to 20% of the total flora, but did not appear to correlate with river position or canopy composition. Our data provide quantitative vegetation descriptions of reference wetland standards for a hydrogeomorphic model for this river system.