泥石流流域系统的超熵

SUPERENTROPY IN DRAINAGE-SYSTEM OF DEBRIS FLOW

超熵是用以表征流域系统稳定性的新型定量指标。本文提出了以沟谷纵剖面形态指数N表达超熵数学式,并以成昆、南昆铁路沟谷为例,试用手泥石流沟的判别与活动性评价。

Superentropy in drainage - system expressing non - linearity and non - balance entropy was advanced by Yue and Ai (1989), and could more represent stability of a drainage -system, because ordinary drainage -system is a geomorphical dissipative structure which is far from the balance. Model shape of a small basin, particularity a debris flow basin, is fanned or rhombus. For a small and ideal basin with uniform conditions producing water and sand, the strahler's curve is h/H= (a/A)N/2. So, the superentropy in a small basin can be expressed by a forming index N of longitudinal profile of a valley as:The formula expressed the superentropy by the N make to calculate the ?xP to be simple, and find audio -visual relation between the ?xP and stability and development of the basin.Firstly, evolutional period of the debris flow basin on geomorphology can be divided by the ?xP value and corresponding value N. Demarcation value of the ?xP between stable and non-stable basins is 0, and corresponding N is 2. As the ?xP<0 or the N<2, then the drainage - system is not stable and belongs to a growing period on geomorphology, and as the ?xP≥O or the N≥2, then the drainage-system tends to stable and belongs to a old period.Further, geomorphic stage on mobility of the debris flow can be divided by character- istic values of the ?xP and corresponding value N.The topographic factor represented by the N is essential but is not ample because of other factors forming debris flow have yet a good lot. Thus the ?xP or the N can be one of main indexs for differentiation and appraisal of the debris flow.Finally, the paper tries to use the superentropy and the N value for differentiating debris flow valley and appraising activity of the debris flow with Chengdu - Kunming and Nanning-Kunming railways as examples. In the examples, disparity of the values N between the valleys, where the debris flow is growing or nothing, is obvious. Serious degree and property of the debris flow is related to the value N also. The result is more satisfied.