Effects of Sand Dune and Vegetation in the Coastal Area of Sri Lanka at the Indian Ocean Tsunami
Effects of Sand Dune and Vegetation in the Coastal Area of Sri Lanka at the Indian Ocean Tsunami
复制标题
印度洋海啸对斯里兰卡沿海地区沙丘和植被的影响
DOI：
10.1142/9789812708915_0015
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发表时间：
2006
影响因子：
1.5
通讯作者：
M. Mowjood
中科院分区：
文献类型：
--
作者：
N. Tanaka;Y. Sasaki;M. Mowjood
本研究以2004年12月26日印度洋海啸发生后的实地观测为基础，探讨了海岸植被和沙丘对海啸防护的影响。根据代表植被的生境和树木的林分结构，将其分为六种类型。利用观测到的树种特征，分析了植被结构对阻力的影响。阻力系数（包括树木的垂直结构Cd_（all）和单位面积植被厚度dNu（d：树木的参考直径，Nu：单位面积的树木数））随树种分类而变化很大。通过野外调查和数据分析，发现红树林中的针根型（Rhizophora apiculata）和红根型（Rhizophora mucronata），以及生长在海滩沙地上的代表性树种露兜树（Pandanus odoratissimus），由于其复杂的气生根结构，在海啸灾害中的防护效果尤为显著。通过对代表性树木的拉拔试验，研究了树木的断裂力矩。断裂力矩的阈值进行了比较，位于海啸损坏的网站上的树木上的阻力矩。破碎力矩方程较好地反映了代表性物种对海啸高度的限制。它得出了一个关于哪种物种能更好地承受海啸波影响的假设。沙丘和泻湖是斯里兰卡海岸带大部分地区的典型景观。沙丘与植被的组合对海啸的阻延起着重要的作用。在垂直方向上，两层森林的P。小乔木和大乔木的水平森林结构对增加阻力、截留漂浮物、断枝、房屋和人也很重要。在今后的沿海景观规划、恢复和海啸灾害测绘中应考虑到这些信息。
This study explored the effects of coastal vegetation and sand dune on tsunami protection based on field observations carried out after the Indian Ocean tsunami on December 26, 2004. The representative vegetation was classified into six types according to their habitat and the stand structures of the trees. The impact of vegetation structure on drag forces was analyzed using the observed characteristics of the tree species. The drag coefficient, including the vertical stand structures of the trees,Cd-all, and the vegetation thickness in a unit area,dNu(d: reference diameter of trees,Nu: number of trees per unit area), varied greatly with the species classification. Based on the field survey and data analysis,Rhizophora apiculataandRhizophora mucronata(Rhizophora apiculata-type), kinds of mangroves, andPandanus odoratissimus, representative tree that grows in beach sand, were found to be especially effective in providing protection from tsunami-damage due to their complex aerial root structures. The breaking moment of the trees was investigated through a pulling test for the representative trees. The threshold value for breaking moment was compared to the drag-force moment acting on the trees located at the tsunami-damaged site. The breaking moment equation represents well the limitation of the representative species with the tsunami height. It arrives at a hypothesis about which species could better withstand the effects of a tsunami wave. Sand dune and lagoon is a typical landscape in most part of the coastal zone of Sri Lanka. The combination of the sand dune followed by vegetation toward landside played an important role in retarding tsunami. Two layers of forest in the vertical direction withP. odoratissimusandCasuarina equisetifoliaand a horizontal forest structure of small and large diameter trees were also important for increasing drag, trapping floating objects, broken branches, houses, and people. These information should be considered in future coastal landscape planning, rehabilitation, and tsunami hazard mapping.