الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 284 |  |  |
| | | from | 284 | | |
Abstract
Khor Arbaat is the main source of water supply for Port Sudan City, which is the capital of the Red Sea State, and second City in Sudan after Khartoum. Khor Arbaat originates from the Red Sea Hills and empties its water into the Red Sea Coast. Khor Arbaat is about 50 km to the city, and the Wadi has a length of 160 km with steep slope of 6 – 10 m per one kilometer which to high velocity of up to 4 m/sec. Therefore the Khor carries large quantities of sediments (up to 1553113.44 tons annually), which deposit in dams’ reservoirs during the flood periods. Khor Arbaat receives high flood in summer (June, July, and August) and winter (November, December) seasons, but these quantities of water are useless.
There are three dams constructed on the Khor; Upper Gate Dam 1, Sea Port Corporation Dam 2, and Fourth Reservoir Dam 3 were designed for the water supply of Port Sudan town, they generally suffer from siltation and their storage capacity is decreased due to floodwater. The steep slopes of the watershed, the high rainfall, the soil type of the watersheds area, the less vegetation cover make the situation more conductive for greater erosion to take place in the Khor Arbaat catchment during rainy seasons.
This study aims to reach the optimum design of dams located on steeper slope areas such as Khor Arbaat in Eastern Sudan, and contribute to any mitigation measures that can be taken in order to reduce the amount of sediment inflow. This study proposed sediment settling basin to remove sediments by settling them into the basin.
The physical , topographical and hydrological characteristics of the watershed was related to the design of settling basin through developing the digital elevation model (DEM), watershed delineation, stream networks using GIS capabilities.
In this research, the total sediment loads were computed and the annual quantities of sediment which will be deposited in settling basin in future were predicted. In this study analysis was carried for thirty two sediment bed materials samples from different locations within upstream and downstream of Khor Arbaat dams. Sediment grading curves of bed materials samples were determined using sieve analysis, hydrometer test, and Atterberg limits. The grading curves described the sizes, distribution and pattern of deposition of sediment particles. The field investigation also included the siltation measurements inside Upper Gate Dam1 and dry siltation inside SPC Dam 2. GPS and GIS applications were used for determine samples location and other measurements.
In this research; Rainfall- Runoff process for Khor Arbaat watershed that lies in the northwest coast of the Red Sea was studied, the drainage watershed that contributes to seasonal floods was described, and the surface runoff volume, flow peak and flood hydrograph were predicted using HEC-HMS3.5 Model. Statistical rainfall analysis was done for yearly, monthly, daily rainfall data gauging stations surrounding the Arbaat watershed. The consistency of rainfall data was verified, and the areal rainfall was estimated using the Isohyetal Map of the area, the results were used as input to the HEC-HMS meteorological component.
The Rainfall- Runoff study for this research is important to estimate the daily suspended sediment load (Ton/day) from surface runoff of Khor Arbaat using (Qs = 0.00864.C.Qw).For estimating suspended sediment concentration (SSC); Turbidity (NTU) water quality values are transformed to (SSC) using linear and noun linear equations. The turbidity method led to suitable values of concentration to estimating the annual suspended sediment discharge. However, for estimate sediment bed load; Strand and Pemberton Procedure (15 - 35 % as suspended load) was used.
For the selection of the best location of sediment settling basin; the research proposed to be located 8.6 kilometers downstream of U/S Upper Gate Dam 1 on Khor Arbaat. This proposed location was selected using Satellite Images and largest cross-sectional area within minimum flow velocity by Global Mapper 13.0 & OriginPro.8.
To design Arbaat Settling Basin; the design of basin depends mostly on the sediment particle sizes entering to the basin and it’s settling velocities and flow discharge diverted through the basin. This study used theoretical and empirical equations to determine the appropriate size (Lb*Wb*hu) of basin to trap a fraction of the sediments targeted by the design. The optimum settling basin dimensions which seem to be suitable are 1500x 500 x 2.0 m. Also, for these settling basin dimensions, the detention basin should be enough to receive about 59% of the suspended sediment load and all the sediment of sizes larger than 0.03 mm should be settled in the settling basin with basin trap efficiency 63.2%. Settling Basin design is proposed as sediment control strategies to achieve the long-term sustainable operation of Khor Arbaat dams, beside heightening and maintenance of the existing dams and enlarging the storage capacities of new dams in future. A key to optimizing the design of these dams which are located in steeper slope areas to sustain its long term operation; install accurate suspended sediment concentration gauging stations, and install accurate flow and rainfall gauging stations along the Khor.
The Economic study for this research is significant to select the feasible supply of water to the Pot Sudan town; the study shows that the Sediment Settling Basin at the present time is suitable. Because the cost of Settling Basin construction (50*106 Dollar) is feasible and provided 105,000 m3 /day, compared with the cost of Water Desalination and Water from River Nile at Atbara (300*106 - 550*106 Dollar).