Whangārei Harbour Sedimentation Report

The Northland Regional Council and Northport commissioned NIWA to determine historical rates of sediment accumulation and contemporary sources of catchment sediments depositing in the Whangārei Harbour system.

The results of this study will provide resource planners, politicians and the public with valuable information regarding sediment accumulation rates and the present-day sources of sediment accumulating in the Whangarei Harbour system. This together with previous studies of sedimentation in the Kaipara Harbour and the Bay of Islands system will help NRC to make informed management decisions on activities that contribute to sediment erosion and prioritise land management initiatives to reduce sediment erosion and runoff to estuaries. In addition, NRC is working with the Whangarei District Council and the community to develop a catchment management plan for the Whangārei Harbour. The information from this report will be valuable for the development of water management objectives, limits, and targets for the harbour catchment.

Due to the size of the document it has been broken into the following parts and can be downloaded below:

Part 1

Executive summary

1 Introduction
1.1 Background
1.2 Study objectives
1.3 Recent sedimentation in NZ estuaries and coastal marine environments
1.4 Study area

2 Methods
2.1 Strategy
2.2 Mud-transport modelling
2.3 Sediment accumulation rates
2.4 Long-term catchment sediment yield
2.5 Sediment source determination

3 Results
3.1 Modelled sedimentation patterns

Part 2

3 Results (continued)
3.2 Sediment accumulation rates
3.3 Spatial variations in recent sediment accumulation rates

Part 3

3 Results (continued)
3.4 Long-term average catchment sediment yield
3.5 Contemporary sediment sources

4 Synthesis
4.1 Recent sedimentation history of Whangarei Harbour
4.2 Sediment accommodation space and sea-level rise
4.3 Influence of catchment deforestation on sedimentation rates
4.4 Catchment sediment yield
4.5 Comparison of sedimentation rates in North Island estuaries
4.6 Sediment sources

5 Acknowledgements

6 References