不同海岸防風林型態與風速之關係試驗

The Relationship Between Different Windbreak Types in coastland and Wind Velocity

江永哲(Yung-Cheh Chiang) ； 游繁結(Fan-Chieh Yu) ； 黄隆明(Long-Ming Huang)

《中華水土保持學報》 18卷1期 (1987/05) Pp. 14-26

https://doi.org/10.29417/JCSWC.198705_18(1).0002

摘要

由於目前海岸防風林之營造所採樹種係以木麻黃單純林爲主，因此以往有關海岸防風林功效之試驗，係多針對木麻黃單純林加以探討，本文爲瞭解不同海岸防風林型態與風速之關係，特別勘選其他樹種之單純林、或有混交、或有築堤造林等不同型態之海岸林，以探究其彼此間對於防風性能上的差異。爲此，本文分別選擇竹灣、小門、麥寮、竹圍等具有不同型態之海岸防風林爲試驗地，測定其林前、林後不同位置之風速垂直剖面分佈，並根據動量方程式之理論求算林帶阻力係數，以比較不同防風林型態差異之效果，由試驗結果得如下之結論：（1）海岸防風林其阻力係數値隨林帶寬度之增大而增加，特別在林前進入林帶中時阻力係數急速增加，顯然可見防風網及防風林之功效。（2）混交林之林帶阻力係數高於木麻黃單純林，顯然混交林有較強阻抗風力之效應。（3）築堤造林地之林帶阻力係數高於一般造林地，顯然築堤造林有較強阻抗風力之效應。（4）落葉前後木麻黃單純林之林帶阻力係數高於黃槿單純林，顯然木麻黃單純林有較強阻抗風力之效應。

並列摘要

Since coastal windbreaks had mainly been built of the pure stand of Casuarina, there were many experiments and discussions concerning the efficacy of coastal windbreaks for the sake of researching the pure stand of Casuarina. Therefore, in order to comprehend the relations between various styles of coastal windbreaks and wind velocity, and moreover, to find out the differences in efficacy among different windbreaks, we have chosen many other plants and built them in different ways, such as pure stand, mixed stand, embankment afforestation, etc. We took Chu-wan, Hsiao-men, Mai-Iiao, and Chu-wei as our experimental regions just because of those various styles of coastal windbreaks. We measured the distribution of perpendicular profile of wind velocity in many different positions from the front to the back of the stand, and then put the drag coefficient into calculation by the theory of momentum equation to compare the distinction (in efficacy) of diverse windbreaks. According to our experimental results, we can conclude as follows: 1. The drag coefficient becomes greater in proportion to the width of the windbreaks, and it rapidly increases especially when entering the front windbreaks. It shows that windbreaks and windbreak nets take great effect to resist wind. 2. The drag coefficient of mixed stand is larger than that of the pure stand of Casuarina. Apparently, mixed stand is better for reducing wind velocity. 3. The drag coefficient of embankment afforestation is larger than that of common windbreaks. It is apparent that embankment afforestation can produce more efficacy to resist the force of wind. 4. Whether the leaves fall or not, the drag coefficient of the pure stand of Casuarina is larger than that of the pure stand of Hibiscus Tiliaceus Linn. It is evident that the pure stand of Casuarina can produce more efficacy to resist the force of wind.