Measuring peatland channel erosion in the high Andes from very high-resolution DEMs

The bofedales (high-altitude peatlands) of the tropical Andes are a critical source of water and forage for local camelid livestock, but local reports and field observations indicate increasing degradation in many areas. Channel erosion caused by increased glacial runoff or precipitation is one possible explanation. The objective of this study was to evaluate this hypothesis by developing a method for measuring channel incision in high-resolution DEMs (digital elevation models), and then testing whether a relationship existed between the degree of channel incision and apparent bofedal health. DEMs were generated from high-resolution ( 0.5 m), commercially-available DigitalGlobe stereo image pairs, and verified using a limited set of available field measurements. Channel depth, width, and cross-sectional area, as well as peatland slope, was then manually obtained for a number of randomly selected bofedales. Mean NDVI was used as a proxy for bofedal health, and was obtained from Landsat imagery. A multiple linear regression was conducted to assess the degree to which the explanatory variables (channel depth, channel width, channel cross-sectional area, and bofedal slope) could predict peatland NDVI. We will present details of the DEM generation, characterization of channel incision and bofedal topography, and links to bofedal health as measured by NDVI.