Climate change intensifies urban water challenges. Although water-sensitive urban design (WSUD) offers adaptive solutions, its implementation remains fragmented at catchment scale. This study addresses the lack of catchment-scale planning by automating P. A. Yeomans' agricultural keyline planning logic into a digital terrain analysis workflow. Using the SAGA geomorphon landform classification algorithm in QGIS, the methodology was tested on the Sandy Creek sub-catchment (3.2 km²) in Brisbane, Australia, with parameters optimised at a 1000m radial limit and 0.5° threshold angle. Analysis identified 1362 hollow zones, 75 of which exceeded the 500 m² significance threshold. Landuse analysis showed that 36% of these key points were on council land and 41% were within residential parcels. Validation against five historical reservoir locations confirmed spatial alignment within 100 m of all sites. This open-source workflow provides a data-driven framework for catchment-scale stormwater management that overcomes WSUD fragmentation using terrain-informed hydrological logic.