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The Potential Effect of Sea Level Rise on Estuarine Vegetation: Pilot Study - Coromandel Harbour

TR 2007/05
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Report: TR 2007/05

Author: Meg Graeme (Natural Solutions) and Jim Dahm (Eco Nomos Ltd)

Abstract

This pilot study aims to help Environment Waikato identify the potential impact of projected sea level rise on the extent and distribution of estuarine vegetation within Waikato estuaries. In particular, the report examines the potential influence of surrounding land uses on the response of estuarine vegetation to sea level rise.

Coromandel Harbour was chosen as the pilot study site as it has a range of different land uses around the harbour margin typical of the increasing human pressure on Waikato estuaries – including agricultural and urban land uses. The study investigated the influence of sea level rise and surrounding land use on estuarine vegetation in sites with different wave exposure and an area where estuarine wetland has already been significantly modified by human activities.

The objectives of the pilot study are to:

  1. Identify the factors influencing the boundaries of vegetation communities with existing sea level, particularly bed level and the effect of different wave exposure.
  2. Survey the harbour and low-lying harbour edge to identify areas where wetland vegetation might expand to with predicted sea level rise.
  3. Examine implications of various sea level rise scenarios for wetland loss/expansion.
  4. Identify any relevant recommendations for the management of harbour margin land uses to ensure the protection of estuarine wetland vegetation in the event of projected sea level rise.

The Potential Effect of Sea Level Rise on Estuarine Vegetation: Pilot Study - Coromandel Harbour [PDF, 1.1 MB]

Contents
1 Introduction 1
2 Objectives 2
3 Methods 2
3.1 Estuarine Vegetation Communities 2
3.2 Surveying and Study Sites 3
3.3 Analysis 3
4 Results 4
4.1 Survey Benchmarks and Tidal Parameters 4
4.2 Species Occurrence 5
4.3 Response to Most Likely Sea Level Rise 7
4.3.1 Exposed Site 9
4.3.2 Moderately Exposed Site 11
4.3.3 Modified Area - Long Bay Road Wetland 13
5 Conclusions and Management Recommendations 15
5.1 Summary of Conclusions 15
5.2 Recommendations 17
  References 42
  Appendices 43
Appendix 1: Estuarine vegetation communities 43
Appendix 2: Benchmarks 49
Appendix 3: Additional cross-sections 52