Integrated rainfall–runoff and flood inundation modeling for flash flood risk assessment under data scarcity in arid regions: Wadi Fatimah basin case study,Saudi Arabia

This paper presents a proposed integrated approach for flood hazardous evaluation in arid and semi-arid areas. Wadi Fatimah in Saudi Arabia is utilized for implementation of such an approach. The approach consists of four stages. In the first stage, a statistical analysis of rainfall data is performed to determine the design storms at specified return periods. In the second stage, geological and geomorphologic analyses are followed to estimate the geomorphic parameters. The third stage concerned with land use and land cover analyses linked with hydrological analysis to estimate the hydrographs. The fourth stage is related to the delineation of the inundation area under two scenarios: the presence and absence of the dam. The statistical analysis proved that some rainfall stations do not follow a Gumbel distribution. The presence of the dam reduces the inundation depth by about 10 %. The reduction in the inundation area due the presence of the dam is about 25 %.     

Effect of temperature, pressure, salinity, and surfactant concentration on IFT for surfactant flooding optimization

In this research, effect of temperature, pressure, salinity, surfactant concentration, and surfactant type on interfacial tension (IFT) and critical micelle concentration of Saudi Arabian crude oil and various aqueous phases were investigated. The temperature ranged from ambient condition to 90°C, and the pressures were varied from atmospheric to 4,000 psi (27.58 MPa). Surfactant solutions were prepared using several aqueous phases, i.e., purified water, 10% brine consisting of 100% NaCl, 10% brine consisting of 95% NaCl and 5% CaCl₂, and 10% brine consisting of 83% NaCl and 17% CaCl₂. Out of 13 commercial surfactants, only three surfactants showed good solubility in pure water and brine. Those are Zonyl FSE Fluorosurfactant®, Triton X-100®, and Triton X-405®. Therefore, they were investigated thoroughly by measuring their efficiency in reducing the crude oil-aqueous phase IFT. Based on this screening process, laboratory surfactant flooding experiments for crude oil recovery were conducted using Triton X-405 and Triton X-100. The chemical flood was made at both original oil in place and at residual oil in place subsequent to conventional water flooding. Based on the obtained results, both surfactants were efficient, and more oil was recovered than that obtained through water flooding. Comparing both surfactant solutions, it was observed that Triton X-405 was more efficient than Triton X-100 at the same surfactant concentration and reservoir conditions.     

Investigation on crude oil penetration depth into soils

The main objectives of this paper are to study crude oil migration as a toxic fluid, its rate of penetration, and its consequences for eventual treatment. To achieve these objectives, an experimental model was designed comprising two separated columns, filled with soil and other rock types to simulate a real case scenario. Crude oil penetration depth versus time was recorded by taking soil samples whereas water samples were collected from the wet system to analyze the penetrating liquid. The results show that penetration depth was greater in the wet system during the early stages rather than in the dry system. However, with time, penetration becomes more developed in both systems. Overall penetration in the final stage was found to be significantly higher in the dry system. In addition, it was observed that during crude oil migration in dry system, chromatographic separation of crude oil components has occurred obviously. The obtained results reveal that immediate treatment must be performed in both systems but particularly in the wet system, due to its higher initial penetration rate.     

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

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.     

Influence of temporal fluctuations and spatial heterogeneity on pollution transport in porous media

The combined influence of temporal fluctuations and spatial heterogeneity on non-reactive solute transport mechanisms in porous media can be understood by performing simulations of steady and unsteady flow and transport in heterogeneous media. The study focuses on issues such as the degree of heterogeneity, correlation length, separation of the combined effects of temporal and spatial variations, and ergodicity conditions under unsteady flow conditions. It is shown that the effect of temporal variations on solute transport is masked by the strong effect of spatial heterogeneity. There is no obvious difference in plume shape between steady and unsteady flow conditions; the first and the second spatial moments of the plume of the unsteady-state flow condition fluctuate around the steady-state flow condition with the same period of oscillations as the input signal at small storage coefficient (S????0.001). At a relatively high standard deviation in hydraulic conductivity and a small storage coefficient, the unsteady flow condition sharpens the temporal variations in macrodispersion coefficients. The magnitude of the longitudinal macrodispersion coefficient under unsteady flow condition is almost doubled at the maximum values. However, the transverse macrodispersion coefficient fluctuates around zero. The Kubo number and Peclet number ranges are 1.2?C64 and 10?C250, respectively.     

Stochastic modelling of a diffusive wave for flood propagation using the random walk particle tracking method in a hypothetical city

Deterministic numerical schemes have been widely used for the solution of the diffusive wave (DW) equation, however, these schemes are computationally costly and suffer instability issues. This paper presents a stochastic random walk particle tracking (RWPT) method to solve such an equation for a dam‐break flow problem. Three different wave duration scenarios are presented for simulations of the DW for flood flows in a hypothetical city. The hypothetical city is represented by a domain of size 2,000 m by 500 m in x and y directions, respectively. The domain is divided into 25 m by 25 m cells. A dam is located at the upstream of the hypothetical city. Each scenario has a distinct propagation pattern after the dam is breached. Analysed and presented are 18 different simulations, which are composed of three different building configurations, two different bed slopes, and three different shapes of hydrographs. In this method, the flood volume is divided into a large number of particles where each particle carries a fixed amount of the flood volume. These particles undergo convective and diffusive movements, and their superposition represents propagation of the DW in the flow domain. The solution algorithm of the RWPT‐based equations is used to compute flood inundation depths in the hypothetical city. Comparison is drawn among the simulated results from three different shapes of the inflow hydrographs. The proposed stochastic method has two major advantages over traditional deterministic schemes: (a) greater efficiency, thus lesser computational costs, and (b) no instability issues.