Applying Logistic Regression Method to Analyze the Effects of Landslide on Rainfall Threshold Value for Debris Flow Warning –Using the Watershed of Chenyoulan Stream as An Example
Date Issued
2012
Date
2012
Author(s)
Zeng, Xun-Yuan
Abstract
The main purpose of this study is to investigate the effects of landslides and other physiographic factors on the rainfall threshold value for debris flow warning and then to evaluate it. In Taiwan, the rainfall threshold value for debris flow warning has been used for years as a basis to announce debris flow warning and it is amended annually or after the event of great mass movement disasters.
The site of this study was selected at Chenyoulan stream watershed. The statistics examines to landslide ratio, the average riverbed slope steepness , effective watershed area , form factor of watersheds and the debris flow take place higher relativity of physiographic factor, and among them with landslide ratio and debris flow to establish relationship most for notable. Then, with method of logistic regression was used for analysis, building a model to assess rainfall threshold value for debris flow warning with landslides and other physiography factors. In the meantime, compare the effect of two different rainfall-field division ,and the influence of physiographic factor conversion of membership function. From the result, Fan et al.(2003) the rain-field division method and the mode of has been convert to membership function physiography factor the best, the accuracy rate of debris flow occurrence reaches to 80% above. Therefore, consider the debris flow warning usually more conservative standard to publish a warning notice, this results to build a debris flow warning mode.
Deduce of the physical mechanism of mode and debris flow occurrence mutually matches. While landslide ratio (DN), average riverbed slope steepness (SN) and effective watershed area (AN) and form factor of watersheds (FN) increment, it takes place a probability to also immediately increase. If the debris flow takes place a probability(p) homology, the rainfall threshold value for debris flow warning to reduce while landslide ratio(DN), average riverbed slope steepness (SN) and effective watershed area (AN) and form factor of watersheds(FN) increment. This debris flow warnning mode, after to provide major disaster (as earthquake, typhoon pouring rain) ,through examine the quantity of four kinds of physiographic factors, is rapid to revise the rainfall threshold value for debris flow warning ,is well timed to reflect now condition.
Subjects
rainfall threshold value for debris flow warning
logistic regression
landslide
debris flow
Type
thesis
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