Analyses of gravity grain flows

This investigation consists of two separate parts. In the first part the subaqueous flow of a cloud of coarse particles down an inclined bed was investigated experimentally and theoretically. This work is relevant to the mechanics of transportation of ocean bed sediment in the form of submarine grain flows. It was found experimentally that after an initial growth period, the cloud collapsed as a result of sedimentation. A theoretical analysis for the development of a two-dimensional cloud was derived based upon the overall conservation equations; the sediment mass balance equation, the ambient fluid entrainment equation and the linear momentum equation along the bed.The second part of the thesis is a study of the flow and spreading of a finite mass of dry cohesionless granular material released from rest on rough inclines. Firstly, a two-dimensional depth-averaged model which describes both the longitudinal and the lateral spreading during flow down a rough inclined plane was developed. From the results of the numerical studies, it was concluded that the lateral spreading is insignificant relative to the longitudinal spreading. Therefore, a depth-averaged model which describes the one-dimensional longitudinal spreading down rough, curved beds was developed. It was concluded that the traveling distance and velocity of the center of mass of a rock pile can be approximately predicted by a simple analysis of a point mass sliding down the same incline. The long runout distance of the leading edge of the slide debris can result from extreme spreading of the pile as it accelerates down the slope after initial release

Hydrological assessment of some old dams in Saudi Arabia under the current climate, environmental conditions, and the use of the advanced technology

Abstract Dams were built in Saudi Arabia (SA) starting from the late fifties. The rainfall record at that time is rather short since the early rainfall records in the study area were in the mid-sixties. Therefore, due to the recent changes in climatic conditions worldwide and having longer rainfall records nowadays, it is very important to assess the existing dams under the current conditions. The assessment is based on some criteria: the length of the rainfall records, the rainfall storm hyetographs, storm duration, the type of the rainfall frequency distribution, topographic data, and the current land use/land cover conditions. Fourteen dams in the Riyadh region are chosen, as a pilot study, to perform the proposed dam evaluation procedure. Later, the study can be extended to any region in SA. The results show that increasing the record length leads to a convergence of the rainfall to an asymptotic value. The minimum record length to produce stable statistical rainfall is about 20 years. Nine out of fourteen dams have a storage capacity less than the 5-year return period. The statistical analysis showed that the measured rainfall in some past years corresponds to 50 and 100 years return periods. Gumbel Type I distribution, which was used in the analysis of the old dams, does not seem to be the best distribution under the recent climate data. The dams should also be assessed under the effects of climate change and urban expansion

The impact of rainfall distribution patterns on hydrological and hydraulic response in arid regions:case study Medina, Saudi Arabia

Abstract Rainfall distribution patterns (RDPs) are crucial for hydrologic design. Hydrologic modeling is based on Soil Conservation Services (SCS) type RDPs (SCS type I, IA, II, and III). SCS type II method is widely used by hydrologists in arid regions. These RDPs were designed for the USA and similar temperate regions. There is no scientific justification for using SCS type II method in arid regions. The consequences of using SCS type II have impacts on the hydrologic and hydraulic modeling studies. The current paper investigates the validity of the SCS type II and in arid regions. New temporal RDPs were applied and compared with SCS type II RDPs. The produced peak discharges, volumes, maximum inundation depths, top widths, and velocities from both approaches were analyzed. An application is made on the protection channel in Taibah and Islamic Universities campuses in Medina, Saudi Arabia. A methodology was followed which included frequency analysis, catchment modeling, hydrological modeling, and hydraulic modeling. Results indicated that there are considerable consequences on infrastructural design, and hydrologic and hydraulic parameters if inappropriate RDPs are used. The investigation confirmed that the SCS type RDPs do not reflect the actual flood features in arid regions