Catchment-scale LiDAR-based SedNetNZ modelling in the Upper Waitomo catchment

The Waikato Regional Council (WRC) commissioned this study to model erosion and suspended sediment loads in the upper Waitomo catchment using a LiDAR-based version of the SedNetNZ model. The work built a new digital stream network and landslide susceptibility layer to better represent the catchment's karst landscape, including its sinkholes and subsurface drainage, and used these to model current sediment sources alongside three future erosion mitigation scenarios.

The modelling shows shallow landslides are the largest source of sediment in the catchment, followed by surface erosion and riverbank erosion. Even under full implementation of the most ambitious mitigation scenario, further reductions would still be needed to meet the national bottom line for visual water clarity at the catchment's state of the environment monitoring site, and the report assesses the cost-effectiveness of the different mitigation options.