Integrated hydrological and hydraulic modeling for predicting sediment transport in hydraulic road structure design: the case of oued ait ourir, high atlas, Morocco

The design and sizing of hydraulic road structures, such as bridges and trestle bridges, situated in wadis characterized by high sediment transport rates necessitate a systematic consideration of sediment transport in conjunction with fluid flow dynamics. In our investigation, we employ a sophisticated modeling approach to forecast sediment transport fluxes and deposition heights upstream of the RP 2009 structure along the Ait Ourir River, located within the "Ghdat" wadi watershed in the High Atlas region of Morocco, for a 100-year return period. Despite its recent construction in 2020, the existing structure is already susceptible to clogging following liquid flood events. Our modeling framework comprises a primary "sediment transport modeling" model incorporating 12 semi-empirical formulas, encompassing "local" and "global" sediment transport equations, renowned for their widespread utilization and recognition worldwide. Additionally, auxiliary models and tools, including ArcGIS modeling, HECHMS software, HECRAS hydraulic simulation, and granulometric curve analysis, are employed to calibrate the main model parameters, ensuring precise results. Furthermore, we adopt a confrontational approach with available field data to validate our model outcomes. Our analysis reveals a wide spectrum of specific solid flow values ranging from 0.001 m³/s/m (Einstein) to 2.667 m³/s/m (Schoklitsch). Notably, formulas such as Meyer Peter and Müller, Watanabe, Smart and Jaeggi, Ribberink, Camenen, and Larson, and Parker yield congruent results averaging 0.0028 m³/s/m, with centennial deposit heights akin to experimental measurements (2 m). These results predominantly conform to a dimensionless bedding mode represented by \({a\times \left( \theta -\theta cr\right)}^{b}\) ${a\times \left(\theta ,-,\theta ,c,r\right)}^b$ , characterized by empirical coefficients a and b. Furthermore, our findings suggest the potential extension of these models to river torrential floods (Froude number > 1) with a slope I = 2.6% and d50 = 13.3 mm, indicating broader applicability to sites within the Moroccan High Atlas exhibiting similar hydrological characteristics. While our study underscores the limitations of "global" formulas, it accentuates the significant role of solid transport (bedloading), despite the lack of field data and measurements.