The human impact of reclamation on Auckland east coast creeks Thesis
- Author
- Wintrup, G.
- Year
- 1998
- Journal / Source
- Thesis for Auckland University
- Keywords
- Sedimentation, Reclamation, Mangrove, Salt marsh
- Summary
- This thesis reports on a project set up to establish whether there is a difference between natural and human aided rates of reclamation, based on an assumption that, if water movement is impeded and reduced particularly on the ebb tide, the rate of sedimentation will increase. THREATS IDENTIFIED AND/OR DESCRIBED: reclamation; environment modification SCOPE OF SPECIES, HABITATS AND ECOSYSTEMS IMPACTED: mangrove and estuaries SPATIAL EXTENT OF THREAT STUDIED: Specific sites (Waitaramoa, Waikopua and Okura on the Auckland east coast) were chosen based on the following: the site needed a freshwater flow from a river, creek or pipeline to show runoff from the surrounding catchment and the presence of salt swamp Avicennia marina var. resinfera and salt marsh species such as Juncus maritimus var. australiensis and Leptocarpus similis. TEMPORAL EXTENT OF THREAT STUDIED: see above summary DATASETS USED IN THE ANALYSES: Historical review and anecdotal evidence; mapped distribution of plants; Tidal variations data; sediment accumulation within a 50m2 grid. METHODOLOGY USED TO IDENTIFY AND DETERMINE SEVERITY OF THREAT: Measurement of tidal variations indicated time in and out of water for the specific plant zones (mangrove and salt marsh). Sediment accumulation was measured by using plastic plates placed on the substrate amongst mangroves in a 50m2 grid. Grids were placed 20m from the main channel with rows running parallel with the channel, because all sites had substantial stands of mangroves whereas the salt marsh species varied in abundance from site to site. KEY FINDINGS OF THE ANALYSIS: Reclamation occurred at the impacted sites. However, unexpected results for the sedimentation rates at natural and impacted sites meant that there needed to be a re-evaluation of the time scale on which reclamation occurred.
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