Some new projects are considered in the eastern coasts of Dammam city, Saudi Arabia Dredging operations would significantly alter coast hydrological and sediment transport processes. It is important that the project areas must keep flushing the fresh sea water in and out with good water quality parameters, which are currently facing increased pressure from urbanization and navigation requirements in conjunction with industrial developments. A suspended solids or sediments are expected to affect the flora and fauna in that area. A numerical modeling study in needed to study the effect of dredging and in particular the suspended sediments concentrations (mg/L) changed in the region. The results were obtained using finite element method and Newton-Raphson iterations.
Dredging is critical to maritime trade and many recreational pursuits. Extensive dredging and gravel extraction in those coastal areas are for the purpose of extending the coasts, to build a new fish market, and for other purposes. Effective sediment management tools are of fundamental importance for coastal and water authorities to reduce the costs for maintenance dredging and waterway building activities. In this context reliable in situ data of siltation rates and suspended solid concentrations are a precondition to understand the mechanisms that control sediment transport and to optimize for example strategies for dredging and dumping material. Also for numerical computer models the availability of appropriate validation datasets is essential.
During dredging and disposal operations, there is an increase in the total suspended solids (TSS) in the area of activity. TSS, is sometimes referred to as suspended solids, is a simple measure of the dry-weight mass of nondissolved solids suspended per unit volume of water (usually expressed in mg/L). TSS includes inorganic solids such as clay, silt, sand, etc. as well as organic solids such as algae, zooplankton, and detritus [
Following the progress in surveying technology for field data and computer application, models in 1-D, 2-D and 3-D for sediment transportation have been developed in the cases of rivers, estuaries, lakes and reservoirs (e.g., [2-4]). Fassnacht (1997, [
The proposed fish market location at the eastern part of Dammam city coasts is shown in
culation, deposition/re-suspension and erosion [
The equation of continuity is given by Kolar et al. 1994, [
where
h is mean water depth, m is change in water level, m H is total water depth, m U is velocity component in x-direction, m/s V is velocity component in y-direction, m/s T is time, s Q is injected water, m3/s.
As the continuity equation includes three unknown variables u, v, and h, we need two more equations to complete the solution of the problem. These are given by the momentum equations in two directions
The Coriolis parameter f, is defined as
where is the latitude and is the Earth’s rate of rotation equal to 7.2722 × 10-5 s-1. The wind shear stress parameter, k, is defined as:
and:
Change in water level, m
H Total water depth, m
u Velocity in x-direction, m/s
v Velocity in y-direction, m/s
t Time, s
g Acceleration of gravity, m/s2
The Earth’s rate of rotation, s-1
Latitude, deg
C Chézy bottom friction coefficient, m1/2/s
a Density of air, kg/m3
CD Wind drag coefficient
Fluid density, kg/m3
Wx Wind velocity in x-direction, m/s
Wy Wind velocity in y-direction, m/s
W Wind speed, m/s
uo Velocity of injected water in x-direction, m/s
vo Velocity of injected water in y-direction, m/s.
The momentum equations together with the equation of continuity complete the specification of the shallow water flow problem.
The area of study is divided into small regions of finite elements consisting of 241 nodes (
Two types of inputs exist; either input for each node or input on areal regions. Inputs at boundary nodes were given values so that we obtain a wave fluctuation of 0.5 m mean sea level (MSL). Each node has two unknowns, the flow rate Q and the water surface elevation z.
For N nodes in an inlet system, the total numbers of unknowns are 2N, thus, 2N equations are needed to determine values of the unknowns. The finite difference representations of the shallow-water equations with the boundary conditions and the junction conditions constitute a system of 2N nonlinear algebraic equations. To solve these equations we use the generalized NewtonRaphson iteration method [
Initial results of the model regarding flow directions show that it depends mostly on wind direction and geometry of the region bed (
The model was verified by measured data of TSS contents at sites Dammam eastern coasts [
resulting from natural processes or normal navigation activities [
The transportation of suspended solids Dammam coastal areas are jointly controlled by region inflow, tidal current and bottom vertical shear near the seabed. In this work, a 2D model to simulate the transportation of suspended solids was developed in which the mechanisms of advection, diffusion, flocculation settling of particles, scouring and silting of the seabed and the carrying capacity of wave and tide were involved. The model was run for 10 executive days to simulate sediment transportation and was verified with normal field data. The results showed that the modeled contents of suspended solids matched well with the existing readings. Modeled distributions of suspended reflected basically the overall behaviors of sediment transportation.