Landslide initiation and runout susceptibility modeling in the context of hill cutting and rapid urbanization: a combined approach of weights of evidence and spatial multicriteria

Rainfall induced landslides are a common threat to the communities living on dangerous hillslopes in Chittagong Metropolitan Area, Bangladesh. Extreme population pressure, indiscriminate hill cutting, increased precipitation events due to global warming and associated unplanned urbanization in the hills are exaggerating landslide events. The aim of this article is to prepare a scientifically accurate landslide susceptibility map by combining landslide initiation and runout maps. Land cover, slope, soil permeability, surface geology, precipitation, aspect, and distance to hill cut, road cut, drainage and stream network factor maps were selected by conditional independence test. The locations of 56 landslides were collected by field surveying. A weight of evidence(Wo E) method was applied to calculate the positive(presence of landslides) and negative(absence of landslides) factor weights. A combination of analytical hierarchical process(AHP) and fuzzymembership standardization(weighs from 0 to 1) was applied for performing a spatial multi-criteria evaluation. Expert opinion guided the decision rule for AHP. The Flow-R tool that allows modeling landslide runout from the initiation sources was applied. The flow direction was calculated using the modified Holmgren's algorithm. The AHP landslide initiation and runout susceptibility maps were used to prepare a combined landslide susceptibility map. The relative operating characteristic curve was used for model validation purpose. The accuracy of Wo E, AHP, and combined susceptibility map was calculated 96%, 97%, and 98%, respectively.

Experimental analysis on air-to-water sound transmission loss in shallow water

The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,2013.During the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately.Through analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is evident.The wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics.