Effects of type, level and time of sand and gravel mining on particle size distributions of suspended sediment

Monitoring the sediment transport behavior induced by different interventions, particularly sand mining from rivers, is needed to adaptively manage the watersheds. The particle size distribution of the sus-pended sediment in up and downstream of rivers is one of the main indicators to know about fate of sediments, which may be varied in different conditions. We investigated the effect of some types of sand and gravel (i.e., manual and low, semi-heavy, and heavy machinery) mining on particle size distribution of suspended sediment in the Vaz-e-Owlya, Vaz-e-Sofla and Alesh-Roud riverine mines located in Ma-zandaran Province, northern Iran. The study was conducted on a monthly basis from February, 2012 to January, 2013. Laser granulometry was used to analyze the particle size distribution of suspended se-diment samples taken from up and downstream sections of the study mines. The results revealed that the level and intensity of mining activity affected particle size distribution of suspended sediments. Further statistical assessments in up and downstream sections of the mines proved that sorting, D50, mean, D90, kurtosis, skewness and D10 of the suspended sediment were not significantly influenced by mining activities at levels of 0.09, 0.11, 0.12, 0.15 to 0.69, 0.15–0.69, 0.77, 0.87, 0.97, respectively. While it was not statistically significant, we found that the type of mine and the level of the exploitation changed the particle size distribution of the suspended sediment.

Assessing the health and ecological security of a human induced watershed in central iran

Assessment of the watershed health and associated ecological security is crucial for the proper land resources management,notably when sufficient money and time have lacked.The present study aimed to prepare health and ecological security for the Pishkuh Watershed in Yazd Province,central Iran.To prepare the health atlas of the Pishkuh Watershed,the conceptual framework of pressure,state,response(PSR)was employed.The pressure index was investigated by analyzing the driving forces of natural and human-induced factors.Then,the existing conditions of the natural environment and the watershed performance were analyzed using the state index.Besides,the response index was also calculated as a criterion for expressing the degree of community response or different watershed outcomes to the driving forces imposed on the watershed system.The study results revealed that some 91 and 9%of the watershed were classified as moderately healthy and relatively unhealthy.The results of the ecological security index further showed that some 41%of the area was categorized as relatively poor status.The results of the current study can be used by local managers and decision-makers to adaptively designate appropriate,economic,and goal-targeted solutions for the resources management in the region.