應用碎形理論推估土壤表層之含水量

Estimation of Surface Soil Moisture Using Fractal

何竣璿(Chun-Hsuan He)

指導教授 ： 陳彥璋

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2014年)

https://doi.org/10.6841/NTUT.2014.00764

摘要

土壤含水量為地表蒸發的水文循環中一個重要的因子，其資訊可應用於許多領域，如進行水庫管理、乾旱預警系統、灌溉管理調度與作物產量預估等。而土壤含水量雖可於現地採樣計算，但需要專業的儀器與知識，且採樣僅能得知小面積的資訊，若要得知大面積的土壤含水量需要耗費大量的人力及物力，因較難實行。
土壤表面因乾燥而產生龜裂的現象常被用來描述土地乾旱的狀況，土壤龜裂現象與土壤含水量應有一定之關係，因此本研究以碎形理論（fractal theory）來解讀土壤龜裂所代表的土壤含水量。先以現地採樣的土壤經烘箱烘乾，利用重量法測土壤含水量，並採用盒子維度法（box dimension）將影像中土壤龜裂的裂痕量化成碎形維度（fractal dimension），對應其土壤含水量，建立碎形維度與土壤含水量的關係方程式，進而應用碎形理論的特性推估大面積的土壤含水量的情形。
本研究以石門水庫底泥為樣本建立碎形維度及土壤含水量率定方程式，並以不同溫度、厚度及土壤種類探討碎形維度的變化，實驗得知在不同溫度及土壤厚度太薄時皆會影響碎形維度變化，不同土壤種類因土壤特性不同使土壤表面龜裂的時間和龜裂裂痕數量有所差異，因此各種土壤的碎形維度-含水量率定方程式只限定該土壤使用。

關鍵字

土壤含水量 ； 碎形理論 ； 盒子維度

並列摘要

The soil moisture content is a very important factor in the hydrological cycle of surface evaporation. Its information could be used in many fields, such as reservoir management, early drought warning systems, irrigation scheduling and management, and crop yield estimations. Although soil moisture content could be calculated with in situ sampling, but professional equipment and knowledge are needed and such sampling could only provide information for a small area. In order to obtain the soil moisture content for a large area, a lot of manpower and resources are needed and it is more difficult to implement.
Soil surface cracks due to dryness are phenomenon often used to describe drought conditions. Soil cracking phenomenon and moisture content have a certain relationship, so this study used the fractal theory to interpret the soil moisture content represented by soil cracks. The soil gathered in situ was dried with an oven first, then its soil moisture content was measured using the gravimetric method and the soil cracks in the image were quantized into fractal dimension using the box-counting dimension method, corresponding to its soil moisture. A relationship equation was established between fractal dimension and soil moisture content, so the fractal theory could be used to estimate the soil moisture content of large areas.
This study used sediment samples from the Shimen Reservoir to establish the fractal dimension and soil moisture content calibration equation and used different temperatures, thickness, and soil types to investigate fractal dimension changes. Experiment results showed that fractal dimension changes were affected by different temperatures and thin soil and different soil properties caused differences in the time required in generating surface cracks and the amount of cracks. Thus, the fractal dimension and soil moisture content calibration equation was limited to soil types.

並列關鍵字

soil moisture ； fractal theory ； box dimension

參考文獻

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