Cross-Sections and Dimensions: A LiDAR-Based GIS Tool for Bankfull Channel Mapping

Accurate and reproducible delineation of stream bankfull geometry remains a persistent challenge in environmental planning. To address this gap, we developed the Cross-Sections and Dimensions Tool—an automated, slope-based method for extracting stream cross-sections and estimating bankfull width using high-resolution elevation data. The tool applies a configurable slope threshold to identify bank edges, generates perpendicular cross-sections from a stream centreline, and stores all outputs in a structured geodatabase to ensure transparency and reproducibility.,Validation against expert-delineated bankfull polygons across 191 km of stream length in the Greater Melbourne region, Australia, demonstrated strong spatial agreement, with an average F1 score (a balanced measure of prediction-observation overlap) of 74% and a mean absolute error of 0.6 m in bankfull elevation. The tool was most reliable in larger streams (Strahler order 5 and above) with low to moderate vegetation canopy cover (<80%). Notably, the tool effectively replicated the practical visibility limits of small or indistinct channels typically encountered by human mappers.,This approach advances geomorphic feature extraction by grounding bankfull delineation in deterministic geometry rather than hydrological recurrence or black-box modelling. In practice, it enables scalable, transparent, and repeatable analysis of stream morphology for ecological assessment, infrastructure planning, and catchment management.