Mapping Hydromorphic Areas and Drainage Networks in Tropical Riparian
Zones using Topographic Attributes
Abstract
Riparian areas and channel networks are important landscape
compartments, with key hydrological and ecologic functions. Hence,
defining their spatial boundaries is an important step towards
sustainable riparian management. In tropical countries, riparian areas
are rarely mapped, although they represent a crucial component of local
livelihoods and ecosystems. In this study, topographic attributes
generated with a 30m SRTM DEM were used to delineate wet areas and
stream networks of two small catchments in Central Brazil. The
topographic attributes were the local slope, the slope curvature, and
the Topographic Wetness Index-TWI, respectively. Threshold values of the
selected topographic attributes were calibrated in the Santa Maria
catchment, comparing the synthetic wet areas and drainage networks with
corresponding reference (map) features, and validated in the nearby
Santa Maria basin. Drainage network and wet area delineation accuracies
were estimated with multi-criteria and confusion matrix methods. The
drainage network delineation accuracy was 67.2% and 70.7%, and wet
area prediction accuracy was 72.7% and 73.8%, for the Santa Maria and
Gama catchments, respectively. The delineation errors resulted from
model incompleteness, DEM grid size and vertical inaccuracy, and from
cartographic misrepresentation of the reference maps. The method
performed equal or better than other studies in the literature, and
could be used for preliminary mapping of riparian areas of tropical
catchments.