Sediment (particularly muddy sediments) discharged into rivers, streams and harbours can negatively impact a range of values, including ecosystem health and the way people use water for recreational, cultural and spiritual purposes.
The main habitats monitored are unvegetated sediments (e.g. mud and sand areas) and areas vegetated with salt marsh and seagrass. Degraded habitat is a major contributor to reduced aquatic ecosystem health.
Usage guide: Toggle between tabs to see different sedimentation monitoring summaries. Click and drag the year slider on each map (if available) to see change over time, and hover over map data to see specific values. The chart below the map displays each sites' data temporally, hovering over lines will also show specific values and highlight that site on the map.
The depth of sediment overlying concrete pavers buried at discrete sites provides an indicator of estuary sedimentation. The map shows monitoring site (circles) annual sedimentation over a rolling five year period and the whole harbour average of these values (shaded region). Positive values indicate where there has been sediment deposition (accumulation) and negative values indicate erosion.
See Stevens 2022 for technical methods, data tables, and further information
At discrete fine scale and sedimentation monitoring sites, mud content is determined from laboratory analysis of surface sediment samples, and results are rated against thresholds derived from the New Zealand Estuary Trophic Index. A sample mud content of 25% is considered the threshold above which significant ecological changes in associated macroinvertebrate communities can occur.
See Stevens 2018a, Cummings et al. 2021 and Stevens 2022 for technical methods, data tables, and further information