Towards State-Wide and Province-Wide Wet-Areas Mapping through High-Resolution Digital Elevation Modelling, with Applications.

This presentation presents how high-resolution bare-earth digital elevation models (DEMs) can be used to map seasonally varying wet- to-dry soil moisture conditions across the landscapes of large regions. In so doing, this process can also be used to digitally model and map ridge-to-valley transitions and soil –drainage affected physical and chemical properties and processes. At the base is digital pixel-by-pixel determination of flow direction, and flow accumulation, followed by specific interpretations regarding stream flow initiation, and the elevation rise away from local stream channels and other open-water bodies. This rise is referred to as the cartographic depth-to-water index (DTW), set to zero at all down-slope open-water locations. This modelling and mapping approach has found many applications, including the state-wide wet-areas mapping for the purpose of forest operations planning across Maine, Vermont (USA) and several provinces in Canada (New Brunswick, Nova Scotia, and Alberta). Experiences has shown that using the globally available SRTM data generally leads to generally acceptable flow channel and wet-area maps where forest cover still varies from ridge tops to valleys without cut-over areas. Where this is not the case, it is best to use LiDAR-derived bare-earth DEMs, but these also need carefully programmed hydro-conditioned algorithms to ensure that the resulting flow accumulation patterns conform to actual stream channels across, e.g., roads and along floodplains. Applications pertain to, e.g., optimizing and evaluating hydrological infrastructure placements, scheduling off-road forest operations, and quantifying vegetational distribution patterns by soil moisture regime preferences.