Raglan/Whaingaroa Fine Sediment Study - Catchment and Estuarine Modelling

The objective of the Raglan/Whaingaroa Fine Sediment Study is to simulate water and sediment fluxes from a catchment to an estuary over storm time-scales, by linking catchment, stream and estuarine models. Traditionally coastal ocean and river models have evolved separately because of differences in the dominant physical processes. The study aims to integrate three models: SHETRAN, RICOM and DHI. The study centres on fine sediment generation and transport, as this is the fraction that impacts on estuarine ecology. Field data was required to calibrate and verify the models and an extensive monitoring program was conducted during 2005 and 2006 to capture an event dataset for the catchment, stream and estuary simultaneously.

Six monitoring sites were established on small catchments (91 to 270 ha) in August 2005 with the aim of estimating the sediment concentrations and loads for one flood event. Three sites had forested land use and the remaining three sites had some pasture landuse. Water levels, velocities and turbidity were monitored continuously at all sites. Automatic water samplers were remotely triggered to collect during an event. Event started 24 January 2006, with two discrete flow and sediment peaks. Measurements included rainfall, water level (and calculated flow), turbidity. Automatic samplers used for water/sediment samples. Sediments analysed for grain size.

Raglan Harbour and Catchment

2005 onwards

Rainfall measured with tipping bucket rain gauges at seven sites around the catchment (every 15 minutes). Water levels and velocities monitored at 5 minute intervals by Starflows (Unidata, model 2001) and stored on data loggers (Unidata model 6004-2). Water levels were converted to flow using gaugings, stage-velocity and area relationships. Turbidity was measured with OBS turbidity sensors (5 min intervals). Automatic samplers triggered using a pager took samples every 30 minutes for the first 12 hours, and then hourly. More detailed methods given in McKergow et al. (2007)

Limited samples from Old Mt Rd site - sampler failed/malfuntioned both events - loads not calculated for this site. Other limitations discussed in report.

See NIWA and Waikato Regional Council

Project complete.