RESUMEN
Shallow landslides, triggered by extreme rainfall, are a significant hazard in mountainous landscapes. The hazard posed by shallow landslides depends on the availability and strength of colluvial material in landslide source areas and the frequency and intensity of extreme rainfall events. Here we investigate how the time taken to accumulate colluvium affects landslide triggering rate in the Southern Appalachian Mountains, USA and how this may affect future landslide hazards. We calculated the failure potential of 283 hollows by comparing colluvium depths to the minimum (critical) soil depth required for landslide initiation in each hollow. Our data show that most hollow soil depths are close to their critical depth, with 62% of hollows having soils that are too thin to fail. Our results, supported by numerical modeling, reveal that landslide frequency in many humid landscapes may be insensitive to projected changes in the frequency of intense rainfall events.
RESUMEN
The aggregate relationship between homicide and alcohol availability is well established across a number of national and sub-national settings in North America, Europe and some parts of Asia. However, results linking youth homicide and alcohol availability at the retail level are largely absent from the literature, especially at the city level and across longer time periods. In a multivariate, pooled time series and cross-section study, youth homicide offending rates for two age groups, 13-17 and 18-24, were analysed for the 91 largest cities in the USA between 1984 and 2006. Data for social and economic characteristics, drug use, street gang activity and gun availability were also used as time series measures. Data on the availability of alcohol for each city were gathered from the US Census of Economic Activity, which is conducted every 5 years. These data were used to construct an annual time series for the density of retail alcohol outlets in each city. Results indicated that net of other variables, several of which had significant impacts on youth homicide, the density of alcohol outlets had a significant positive effect on youth homicide for those aged 13-17 and 18-24. Such positive effects have been found for adults in national and neighbourhood level studies, but this is the first study to report such evidence for teenagers and young adults. An important policy implication of these findings is that the reduction of the density of retail alcohol outlets in a city may be an effective tool for violent crime reduction among such youth.