The issues of scouring around a bridge have become prominent in recent research mainly due to recurrent extreme weather events. Thus, designing a bridge with the appropriate protection measures is essential to safeguard it against failure, which may take place due to scouring from high flows resulting from extreme weather events. Bridges may become partially or entirely submerged during extreme weather events such as large floods and are subject to pressure-flow scour, a condition where the flow is directed downward and under the bridge deck, creating an increase in flow velocity and a corresponding increase in bed scour. This study aims to explore the pressure-flow scour depth under a bridge deck without piers in the presence of two vertical wall abutments under clear water experiments. Sixty-six tests were conducted involving the approach flow depth, bed material size, contraction length, contraction width, and bridge opening for both pressure and free surface flow conditions. An empirical equation was deduced to determine the maximum scour depth, which could be applied as a preliminary design for bridges under pressure-flow conditions. The experimental data were used to determine the performance of the earlier models of pressure-flow scour. The results revealed that for pressure-flow conditions, the maximum scour depth increased by a factor between 2.15 and 9.81 times the maximum scour depth under free surface flow conditions. With same flow depth, when the relative bridge length was increased from 5 to 7.5 and 7.5 to 10, the maximum scour depth decreased by up to about 7.4% and 2.3%, respectively. When the relative bridge width was decreased from 5.5 to 5.2 and 5.2 to 4.4, the maximum scour depth increased by up to about 45.6% and 81.2%, respectively.

Scour is the most dangerous hazard that can affect waterways, since it is responsible for more than sixty percent of the failures that have been reported, including the scour that is caused by floods at water structures. The influence of partially free and submerged flow at a pipe culvert on scour bed morphology was experimentally studied. In addition, three different diameters of the pipe culverts that were used with four Froude numbers for seven different water depths upstream of the culverts were included. The results show that at low Froude number for different heights of water, upstream and downstream are slightly different regarding the height of the water. To illustrate, at high Froude numbers, the height of the water has a very slight difference upstream, whereas there is a large and noticeable decrease in water heights and an increase in velocity downstream. When the height of water increases, the scour depth increases upstream and downstream. The increase downstream is more noticeable. That is because the scour increases when the submergence ratio and water velocity increase, in addition to the water depths with high submergence ratios cause a larger scour hole.

The potential effects of Grand Ethiopian Renaissance Dam (GERD) failure on the downstream countries were numerically assessed. Flow discharge reaching Lake Nasser and the corresponding water levels were determined, and the inundated areas were defined as a result of GERD failure. High-resolution digital elevation model was developed with 2670-km length starting from GERD till Aswan High Dam. GERD’s reservoir, urban, and rural lands downstream of the GERD were presented using a numerical model. The modeled areas included parts of Ethiopia, Sudan, and Egypt, not to mention Toshka Spillway. The model areas were not divided into parts because of calculating the water levels at the existence of intermediate dams as model outputs. In case possible failure of GERD, Roseires and Sennar dams could collapse. Meanwhile, Merowe dam can sustain with the operation of its emergency spillway. Wave height reaches 100-m downstream of the GERD and 64-m and 31-m downstream of the Roseires and Merowe dams, respectively.

Realising the need for improving irrigation system management, the Bahr Sanhoor Canal (BSC) was selected as a case study, and the effect of covering a reach with a concrete box culvert where the irrigation canal passes through a crowded rural area on the efficiency of the canal system was examined. The field inspection of the canal system revealed multiple problems. Two alternatives for improving irrigation management were introduced. A local alternative was offered by applying a suitable numerical model to enhance the efficiency of the current status of the canal system, the water level upstream of the covered part reached 13.54 m, this solution will lower the water levels by approximately 2 m, which is below the bank levels at an affordable cost. Additionally, it will help to avoid the risk of inundating the adjacent residential area. A sustainable and environmental alternative was considered to offer a new path in which the covered reach passed outside the residential area. This alternative is permanent and sustainable. Although the proposed second path to the right of the residential area is the long-term recommendation and is sustainable, any path of flow to either the left or right of the BSC will be associated with initial high costs. The two proposed alternatives may help decision makers improve the performance of irrigation systems.

Radial gates are more common than vertical sluice gates for a number of reasons. They are simpler to use, cause less flow disturbance, require less lifting force, and deliver better discharge. Radial gates are commonly used in new barrages, such as the New Assuit Barrage. Prior researchers used physical investigations to study the efficiency of stilling basin downstream radial gates, but physical studies cost a lot of money and time, so numerical solutions should be investigated. The current study aimed to explore numerically the influence of stilling basin shape and baffle block arrangement on the stability of bed protection, near-bed velocity, energy dissipation, and hydraulic jump characteristics downstream of radial gates. Different 12 discharges were investigated, and their results were compared with previous physical results to verify the performance of the numerical results. The results obtained from the numerical model from all trials are almost identical to the physical model results. Five different alternative designs were carried out numerically to enhance the design of the New Assuit Barrage (NAB) spillway stilling basin. Results showed that alternatives 4 (changing the geometry of the basin by removing the end step and concrete slab) and 5 (as alternative 4 in addition to adding rounded baffle blocks presented in two rows arranged in a staggered way) gave good velocity distribution with low turbulence, low values of near-bed velocities, and stability of bed protection. Also, it is more economical because of the lower cost of concrete and excavation.

This study presents one of the first integrated numerical and experimental studies focusing on the effect of pipeline vibrations on canal bed scour for suspended pipelines through extensive analysis, encompassing 300 numerical simulations and 25 complementary laboratory experiments. Numerical outcomes were validated against experimental measurements, demonstrating strong conformity with discrepancies consistently within ±10%, therefore emphasizing the reliability of our numerical modelling approach. The study findings explicitly reveal that scour depth and morphology were substantially affected by pipeline height, vibration amplitude, pipeline diameter, and flow conditions (represented by the Froude number). Specifically, temporal evolution significantly influences scour development, with vibration amplitude playing a particularly decisive role. Increasing the vibration amplitude from a baseline value of (A/D = 0.2) to double, triple, and quadruple this value resulted in respective increases in scour depth of approximately 12, 47, and 71%. A 27% reduction in scour depth when the pipeline diameter is reduced by 40%. The critical influence of Froude number and vibration frequency. Consequently, these quantitative insights underscore the critical necessity of accurately considering pipeline-induced vibrations in the hydraulic design and protection strategies of river-crossing pipelines to effectively mitigate associated scour risks.