Zone Functions Using Remote Sensing

There is an increasing demand amongst resource managers for cost-effective watershed-scale inventories of riparian buffer condition and function. Recent developments in image processing software and decreasing satellite imagery costs enable a new methodology that can help meet this demand. ASTER satellite imagery, which has 15 metre pixel size, is processed with image segmentation software to identify riparian buffers and stands of riparian vegetation. Field data from a stratified sample of locations are used to identify the attributes of the riparian buffers (such as Manning’s n) adjacent to different land uses. Field data are also used to identify the attributes of the riparian vegetation (such as average diameter at breast height and average tree height). These attributes are then spatially extrapolated across a large (16 000 km) watershed using a land use and vegetation classification derived from remote sensing. An independent set of field data is used to assess the classification accuracy and to assess the reliability of the attributes predicted by the classification. The spatially extrapolated attributes are used to calculate indices that describe some of the functions performed by riparian buffers and riparian vegetation at a whole-of-watershed scale. These function indices describe the hydrologic, geomorphic and ecological functions of the riparian zone. The hydrologic index describes runoff interception while the geomorphic indices describe sediment trapping, and bank reinforcement. The geochemical index describes pollutant trapping. The ecological indices describe stream shading and large wood recruitment. This paper contains a description and discussion of these indices, with some illustrative results for the large wood recruitment index. A more detailed description of the theory and results of the large wood recruitment index are contained in a companion paper. KEY TERMS: vegetation mapping; watershed, riparian functions, prioritization