The effects of exposed pipe encasements on the local variation of hydrodynamic and sediment conditions in a river channel are examined. Laboratory experiments are performed to assess the response of water level, flow regime and bed deformation to several representative types of concrete encasements. The experimental conditions considered are: three types of exposed pipe encasements exposed on t...

Depending on their grain sizes (settling velocities), sed iments are t ransported in rivers as bed load, in suspens ion , or as wash load. The coarsest material rolls or bounces along the bot tom as bed load whereas finer material is placed into suspens ion by the water turbulence. The finest sed iments are t ranspor ted as wash load. evenly distr ibuted through the water depth and effectively ...

The effect of using coarse grain in the upper layer of a gravel-based reed bed is investigated. The aim for testing the “anti-sized” arrangement of gravel media is to seek a solution for the practical problem of medium clogging in reed beds that frequently takes place during the treatment of high strength wastewaters. Results from parallel operations of an anti-sized and a conventional “monosiz...

This study addressed a research concern that employing fixed value for the bed roughness coefficient in lowland rivers (mostly sand-bed rivers) is deemed practically questionable presence of mobile and time-dependent changes vegetation patches. Accordingly, we set up 45 cross-sections four streams to investigate seasonal flow resistance values within year. The results revealed significant sourc...

rivers are unstable environments affected by natural or human factors in changing their directions and patterns. in this study, the tectonic effects on the pattern of the gharasou river in the north of kermanshah city have been studied. aerial photos (years 1955 & 1990), satellite images (etm, year 2000) and topographic as well as geologic maps were used as research tools. the procedure of the ...

Abstract—Vegetation affects the mean and turbulent flow structure. It may increase flood risks and sediment transport. Therefore, it is important to develop analytical approaches for the bed shear stress on vegetated bed, to predict resistance caused by vegetation. In the recent years, experimental and numerical models have both been developed to model the effects of submerged vegetation on ope...

The distribution of some heavy metals, namely Cd, Pb, Zn, Fe, Cu, Cr and Mn in epipellic sediments of Igbede, Ojo and Ojora rivers of Lagos was studied weekly in the early summer (November) of 2003. The levels of selected trace metals were determined using Atomic Absorption Spectrophotometer (UNICAM 969 AAS SOLAR). Trends in heavy metal burdens in the sediments revealed weekly variations in all...