Analysis of River Density Characteristics for Debris-Flow-Prone Streams in Taiwan

• Main Authors: Pin-chen Wang, 王品臻
• Other Authors: Chyan-Deng Jan
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/80666051930803403291

碩士 === 國立成功大學 === 水利及海洋工程學系碩博士班 === 95 === The river density of a watershed is an important geomorphic parameter to understanding the distribution characteristics of the debris-flow-prone streams which could help evaluate the potential of debris-flow occurrence. This study established a calculation method to evaluate the river density of the debris-flow-prone streams by geographical information system (GIS) and testified the method by comparing the results calculated by artificial method and GIS method. The testified result shows the results calculated by artificial method are close to those calculated by geographical information system method, when the grid area is between 0.150- 0.225km2, which means the method proposed in this study could estimate the rivers density of the debris-flow-prone streams properly. Then, based on this method, the river densities of 88 debris-flow-prone steams of which basin area were greater than 5 km2 were calculated in this study. The results found the river densities of debris-flow-prone steams lay mostly between 0.5 - 2 km/km2, and more than one half of the steams lay between 1.3- 1.7km/km2. Besides, this study also discussed the relationship of the rivers densities of the 88 debris-flow-prone streams and the other 7 environmental factors (Including the average altitude, basin area, average slope, form factor of basin, annual rainfall, rock property, potential occurring degree of debris-flow-prone streams). The result shows the average altitude, average slope and form factor of basin of 88 debris-flow-prone streams are negatively related to rivers density, which means the factors decrease while the rivers density increases. The relationship between the rivers density and annual rainfall is not obvious. The results of rivers density and rock property shows the rivers densities in volcanic-rock regions are larger than those in the sedimentary-rock regions, while the rivers densities in sedimentary-rock regions are larger than those in the metamorphic-rock regions. The rivers densities of low potential occurring degree streams are smaller than those of medium or higher potential occurring degree streams.