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Estuary sedimentation: A review of estuarine sedimentation in the Waikato region

TR 2005/13

Report: TR05/13

Author: Shaw Mead, Andrew Moores (ASR Ltd., Marine Consulting and Research)

Abstract

Estuary sedimentation is a continual natural process. However, in many instances the activities on the land within a catchment lead to accelerated estuarine sedimentation. This document provides straight-forward descriptions of how estuarine sedimentation occurs and the methodologies that can be employed to evaluate rates of sedimentation. In addition, the available information on sedimentation rates and calculations of the sediment yield of estuaries within the Waikato region are presented. In the future, as new information comes to hand, this document will be continually updated.

Estuary Sedimentation: a Review of Estuarine Sedimentation in the Waikato Region [PDF, 1.9 MB]

Contents
Foreword I
1 Introduction 1
1.1 Defining Estuaries 1
1.2 Estuary Value 3
1.2.1 Ecosystem 3
1.2.2 Cultural Value of Estuaries 5
2 Sedimentation Processes 6
2.1 Sediment Sources 10
2.1.1 Catchment 10
2.1.2 Open Coast 12
2.1.3 The Estuary 12
2.2 Main Sources of Sediment to Estuaries in the Waikato Region 12
2.3 Physical Processes Within the Estuary 13
2.3.1 Flocculation 13
2.3.2 Sediment Transport and Accumulation 15
2.3.3 Sediment Budget 16
3 Monitoring Methods 17
3.1.1 Sediment Cores 17
3.1.2 Bed Level Monitoring 18
3.1.3 Grain Size Analysis 20
3.1.4 Ecological Monitoring 20
4 Sedimentation Information 22
4.1 West Coast 22
4.1.1 Whaingaroa (Raglan) Harbour 23
4.1.2 Kawhia Harbour 23
4.2 Coromandel Peninsula 24
4.2.1 Firth of Thames 25
4.2.2 Te Kouma Harbour 25
4.2.3 Manaia Harbour 26
4.2.4 Coromandel Harbour 26
4.2.5 Whangapoua Harbour 27
4.2.6 Whitianga Harbour 27
4.2.7 Tairua Harbour 28
4.2.8 Wharekawa Estuary 28
4.2.9 Whangamata Estuary 28
4.2.10 Otahu River 29
4.3 Data Limitations 30
5 Waikato Regional Sediment Yields 32
5.1 Estuary Data 32
6 Areas Where More Information is Needed 34
6.1 West Coast 34
6.2 East Coast 36
7 Literature Cited 41
Appendix 1 – A Variety of New Zealand Estuary Types 43
Appendix 2 - Whangamata Estuary Core 45