Design flow estimates require evaluation of catchment properties such as catchment area, catchment slope, and stream length. Detailed terrain data can be expensive to purchase, especially in regional Australia where terrain capture must be commissioned. It has become common practice to supplement terrain data with Shuttle Radar Topography Mission (SRTM) data with a grid resolution of down to approximately 30 m. But when is it inappropriate to use SRTM data? And how does it affect the estimation of design flows? This study examines the accuracy of SRTM data in terms of hydrological properties and results. Detailed light detection and ranging (LiDAR) terrain data is used as a comparison, testing SRTM data’s ability to represent steep, flat and moderate catchments especially in relation to small catchments. Interest was also focused on the delineation of catchments along linear infrastructure where many contiguous catchments can be processed through automated techniques. This study looks to answer the question of when it is or isn’t appropriate to use SRTM data in hydrological studies. The results should help guide future studies and help assess when purchase of detailed terrain data such as LiDAR is necessary.