關渡紅樹林植群變遷之衝擊評估
Resource
Journal of Taiwan Water conservancy, Vol. 53, No. 2, June 2005
Journal
Journal of Taiwan Water conservancy
Journal Volume
Vol. 53
Journal Issue
No. 2
Pages
-
Date Issued
2005-06
Date
2005-06
Abstract
According to the analysis of cross-sectional elevation survey by Water Resources
Agency form 1989 to 2000, authors found that the cross-section of K01, K02 and K03,
which positions were around the Gunadu Nature Reserve, were deposited year by year.
Furthermore, the coverage area of mangrove has increased form 10.5 ha in 1989 to
23.6 ha in 1994. It is found that mangrove can reduce the flow velocity and therefore
speed up sediment deposition.
The quasi-two-dimensional model, NETSTARS, was used to calculate the
flooding impact around this region. The simulated results show that 5 year return
period flood will bypass the dike after increasing 10% of Manning’s n. Moreover, 10
year and 20 year return period floods will also bypass the dike with mangrove spread
effects.
A horizontal two-dimensional model, TABS-2, was also applied in this study to
simulate the sediment transport characteristics of this tidal wetland. The results reveal
that significant sediment deposition occurs due to the extensive root network of
mangrove. The deposition depth is about 1.3mm, 4.5mm and 2.7mm at node 1546,
1740 and 2090 during 2 year return period flood event.
The increase of mangrove in this area has some adverse effects on the river
hydraulic characteristics, including velocity retardation, increase of water surface
elevation and sediment deposition. It is also found that mangrove spread threat Uca
(Thalassuca) Formosensis Rathbun which is an endemic species of the fiddler crab in
Taiwan and now disappeared in Guandu Nature Reserve. It was therefore suggested
that we should take action to prevent this worse condition carry on as soon as
possible.
Subjects
Guandu Nature Reserve, mangrove, wetland, hydraulic simulation, sediment routing, ecological impact
SDGs
Type
journal article
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