SLiX: A GIS Toolbox to Support AlongStream Knickzones Detection through the Computation and Mapping of the Stream LengthGradient (SL) Index The stream lengthgradient (SL) index is widely used in geomorphological studies aimed at detecting knickzones, which are extensive alongstream deviations from the typical concaveup shape assumed for stream longitudinal profiles at steadystate conditions. In particular, SL was practical for identifying anomalous gradients along bedrock stream channels in mountainous catchments. This work presents the GIS toolbox SLiX designed to extract values of the SL index, starting from Digital Elevation Models (DEMs). SLiX is also suitable for the spatial analysis of the SL values, allowing for the identification of landscape portions where anomalous high values of SL occur and, consequently, those catchment sectors where stream channels show peaks in the erosional dynamic. The SLiX main outputs are (i) point shapefiles containing, among stream channels attributes, the extracted values of SL along the stream network analyzed, and (ii) SL anomaly maps in GeoTIFF format, computed through the Hotspot and Cluster Analysis (HCA), that permit the detection of the catchment sectors where the major SL anomalies occur and consequently the principal knickzones. The application of the proposed tool within an experimental catchment located in the Northern Apennines of Italy demonstrated the proper functionality and the potential of its use for different geomorphological and environmental studies. The accurate and costeffective detection of anomalous changes in stream gradient ensured by SLiX is of great interest and can be useful for studies aimed at unravelling the Earth processes responsible of their formation (e.g., active hillslope processes, such as landslides directly interacting with the streambed, presence of geological structures, and meander cutoff). The applications of SLiX have clear implications for preliminary analyses, at a regional scale in different morphoclimatic contexts, for the hydrological management of river basins andor to prevent geological hazards related to the fluvial erosional dynamics.

A D8compatible highefficient channel head recognition method Abstract   As the resolution of DEMs is becoming higher, both the efficiency and accuracy of channel head recognition are important for drainage network extraction. In this paper, a D8compatible highefficient channel head recognition method is proposed. For each potential channel, this method first calculates a geomorphologic parameter series along the flow path, and then determines the channel head by detecting the change point in the series. Instead of directly using one threshold value for a whole region that is still commonly used in D8based methods, the proposed method recognizes channel heads by their local geomorphology one by one. The proposed method is applied with high resolution DEMs for different terrains, and the identified channel heads and extracted drainage networks show good agreement with observations. In comparison with a popular software with stateoftheart channel head recognition method, the proposed one shows similar accuracy but much higher computational efficiency.