花蓮濱海地區保安林變遷及功效之研究

中文摘要 本研究主要以花蓮2618、2602及2635號海岸保安林作為濱海地區保安林之代表，調查海岸林之防災功效及環境特性並加以規劃建議。藉由衛星影像在地景變遷的判識上，可了解保安林帶整體的變化及海岸線的退縮與否，結果顯示，面積增加的有草生地、沙灘沙洲地及建築用地；面積減少的有農業用地及林帶；面積趨於不變的有墓地及軍事用地。2602及2635號海岸保安林因部分面積被海水淹沒後無法恢復營林而解除，林分有逐漸減少的趨勢，其中又以編號2635號保安林的情況較為明顯。 在保安林帶效能分析方面，藉由微氣候調查，其結果顯示，林帶內之照度平均約為林帶外1/150，至於林帶內之日輻射量則平均約為林帶外1/5；夏季時，林帶外平均氣溫較林帶內平均高約2.3℃；冬季時，林帶外平均氣溫較林帶內平均高約0.4℃；林帶內平均氣壓略高於林帶外2mb；相對溼度顯示林內皆為舒適等級；林內則因風速極小仍趨近於零，種種結果皆表示保安林帶確實適合做為防風、避暑避寒及天然遊憩的理想地點。 當林帶寬度為10行，並同時搭配使用C型斷面時，可獲得最佳的保護效果；若進一步採用前後段皆為20行而間距15H（H：平均樹高）之分段式林帶，不但可提升消能效果，更可節省較多用地。 另外為了減緩颱風的破壞力，在2618號保安林區前緣，建議規劃設置防潮林，其林帶幅最小需有30至40 m寬，前端為低木灌叢帶，中間為易萌芽之矮林帶，後方則為高木林帶等所構成。在2602號保安林南側，可參照南濱公園再延續構築土堤設施，不但可阻擋外圍颱風期間強勁潮浪侵襲，且能更有效阻隔強風與保護區。Abstract This study using Hualien #2618, #2602 and #2635 protection forests as examples to investigate the effects of disaster prevention and environmental features of coastal forests and to plan on the recommendations. Identifying the changes of landscapes in satellite images allows the understanding of the overall changes of protection forests and whether the coastlines are moving backward. The results indicate that grasslands, beaches and dunes, and construction sites are increasing in area, while farming lands and forest zones are decreasing in area, with cemeteries and military sites remaining unchanged. Also, #2602 and #2635 protection forests, the latter being particularly obvious, are removed from the current list as they cannot be restored from partially drown in seawater, adding to the tendency of decreased area of forests. The efficacies of protection forest are analyzed by micro-climate study. The results indicate that the average illumination inside the forest zone is 1/150 of that outside; the solar radiation inside the forest zone is on average 1/5 of that outside. The average temperature outside forest zone is 2.3℃ higher than that inside in summer and 0.4℃ higher in winter. The average atmospheric pressure inside forest zone is about 2mb higher than that outside and the relative humidity inside the forest is shown to be comfortable. The wind speed inside the forest is as low as most zero. All these suggest that the protection forest zones really suit an ideal location for wind-proof, escape from summer and winter as well as natural recreation. Many studies conducted in Taiwan and overseas are summarized and indicate that a forest zone brings about best protection when it has a 10-row width with a C-shaped cross-section. And a forest zone in two sections, one at the front, the other behind, each with 20 rows and an interval of 15H (H: average tree height) not only can increase the energy insulating effect but also saves more land. To mitigate the damages caused by typhoon, it is recommended to plan on setting up tide-water control forest the front of #2618 Protection forest zone. Its width should be 30-40 m wide at minimum, consisting of shrub zone at the front, coppice zone that grows from seeds easily at the middle, and tall tree zone at the rear. It is advisable to extend the earth embankment of Nan-bin Park to be constructed south of the #2602 Protection forest, which will not only retard the striking of intense waves during a typhoon but also keep the strong wind away from protected area more effectively.目錄 第一章 緒論 1 一、前言 1 二、研究動機 1 三、研究目的 2 四、研究流程 3 第二章 前人研究 4 一、地景變遷分析之研究 4 二、風速與高度關係之研究 4 三、地形與風速風向分布之研究 5 四、防風林配置及寬度之研究 6 五、木麻黃生長條件之研究 9 六、微氣候相關之研究 9 第三章 試驗地點、材料與方法 11 一、試驗地點 11 (一)基本資料之蒐集 11 1.海岸特性 11 2.氣候 11 3.風速 12 4.雨量 13 5.颱風 13 (二)試區概況 14 1.編號2618號防風保安林 14 2.編號2602號飛砂防止保安林 16 3.編號2635號防風保安林 18 二、試驗材料與方法 21 (一)現況調查 21 1.編號2618號防風保安林 21 2.編號2602號飛砂防止保安林 21 3.編號2635號防風保安林 21 (二)地景變遷之探討 23 1.地景變遷分析之前置作業 24 2.地景類型之分類 26 3.地景類型圖之繪製 26 4.套疊分析 27 5.變遷分析 27 6.衛星影像植被光譜分析 29 (三)微氣候之探討 29 (四)海岸保安林帶寬度之探討 31 (五)海岸保安林帶連貫之探討 31 第四章 結果與討論 33 一、 保安林生態環境現況調查結果 33 (一)編號2618號防風保安林 33 (二)編號2602號飛砂防止保安林 38 (三)編號2635號防風保安林 42 二、地景變遷分析結果 47 三、微氣候調查與分析結果 53 (一)照度觀測結果 54 (二)日輻射量觀測結果 55 (三)最高及最低溫度觀測結果 55 (四)平均氣溫觀測結果 55 (五)相對溼度觀測結果 56 (六)氣壓觀測結果 58 (七)土壤水份觀測結果 59 (八)地溫觀測結果 59 (九)平均風速觀測結果 62 (十)淺丘地形對微氣候影響之探討 62 四、海岸保安林帶寬度（厚度）之建議方案 64 五、分段式海岸保安林之建議方案 66 六、海岸保安林連貫之建議方案 67 第五章 結論與建議 70 一、保安林生態環境方面 70 二、地景變遷方面 70 三、保安林立地環境方面 70 (一)照度及日輻射量 70 (二)最高、最低及平均溫度 70 (三)相對溼度 71 (四)氣壓 71 (五)土壤水份 71 (六)地溫 71 (七)平均風速 71 (八)淺丘地形對微氣候影響 71 四、建議未來關於保安林規劃與經營管理方面 72 (一)規劃生態體系經營模式 72 (二)規劃適宜之林帶寬度（厚度） 72 (三)規劃分段式林帶 72 (四)林帶連貫性之建議 72 參考文獻 7

飛砂移動機制之風洞試驗

This study was to explore the mechanism of Aeolian sand wind erosion. By the wind tunnel experiment, we tried to find out the Aeolian sand characteristics including density, diameter, texture, water content, shape etc. and the relationships between wind erosion amount and primary specific site characteristics of sand diameter, wind speed and water content. The study sites located at the near coast area around Houlong, Yuanli, Da-an and Da-jia in the central part of Taiwan. The densities were in the range of 2.62 and 2.67 g/cm^3 and the particle size distribution mainly ranged in 0.25-0.42 mm. Since the sand content was over 96% of all the samples, the soil texture was recognized as sandy soil by USDA soil classification. The water contents of all the samples were less than 1%: the highest highest observation of 0.967% in Houlong and the lowest one of 0.282% in Da-jia. After the shape analysis, Da-an sample was identified as sphere, Da-jia as flat shape and the others were between. According to the results of wind tunnel, the starting wind speeds of erosion in different diameters were as follows: 5.5-7.0 m/s of 0.15-0.84 mm and 5.0 m/s of <0.15 mm. Furthermore, when the water content below 1.22%, we had the maximum amount of wind erosion. The further study showed Aeolian wind erosion amount would be decreased from 1.22% to 1.84% and the minimum amount was exhibited of 1.84%. This study not only to demonstrate the severe wind erosion in the area but also concluded and identified several important mechanism characteristics of Aeolian sand erosion. We hope the knowledge and the research method could help our government to the urgent preventive contingency process of Aeolian wind erosion.本試驗為瞭解砂粒之移動機制，因而利用風洞進行不同砂粒粒徑、風速及含水率之觀測，實驗用砂取自於後龍、苑裡、大安及大甲濱海地區。砂粒物性實驗結果：各樣區土壤之質地皆為砂土，其密度介於2.62~2.67g/立方公分之間；粒徑分布在0.25~0.42mm者最多；而土壤含水率皆在1%以下，其中後龍樣區0.967%最高，大甲樣區0.282%最低；再由形狀係數得知，大安樣區砂粒接近球形，而大甲樣區則較為扁平。至於風洞實驗結果：砂粒粒徑介於0.15~0.84mm時，其起始風速為5.5~7m/s，又粒徑在0.15mm以下之砂粒，其起始風速為5m/s；當砂粒含水率低於1.22%時，飛砂量達到最大值；含水率由1.24%遞增至1.84%時，飛砂量急遽遞減；而含水率達1.84%時，對砂粒起動之抑制作用達到最大值