The complex dynamic equilibrium state of rivers, in which the amount of deposition and erosion are in balance, has been a fundamental research topic in river engineering. In this research, three advanced machine learning approaches, including M5 Model Tree (M5Tree), Multivariate Adaptive Regression Splines (MARS) and Least Square Support Vector Regression (LSSVR), are employed to gain new insights and develop more accurate methods for assessment of the longitudinal slope (S), water-surface width (W) and mean water depth (D) of rivers in regime state. Geometric and hydraulic characteristic of 85 cross-sections of Gamasiab River (located in western of Iran), Kaaj River (located in southwestern of Iran) and Behesht-Abad River (located in southwestern of Iran) are used to train and evaluate the employed methods (M5Tree, MARS, and LSSVR). Seven different models comprising various combinations of effective parameters influencing regime river geometry (the flow discharge (Q), median bed grain size (d₅₀) and Shields parameter (τ*)), are developed to evaluate the effect of each of these variables on the prediction of the geometry of regime rivers (S, W and D). The M5Tree method outperformed the other approaches with respect to correlation coefficient (R) values of 0.872, 0.951, and 0.770 and Mean Absolute Relative Error (MARE) values of 0.484, 0.102, and 0.126 for slope, width, and depth prediction, respectively. Furthermore, the flow discharge Q was the key variable governing regime channel width and depth while the regime channel slope was found to be mainly controlled by the Shields parameter.

Extreme rainfall–related urban flooding and consequently, basement flooding due to sewer surcharge, has become one of the most significant drivers of disaster losses in Canada. It has been recommended that homeowners living in flood-prone regions protect their properties against basement flooding by installing backwater valves on sewer laterals and branch lines connected to plumbing fixtures. The most common causes of valve failure are identified and categorized into the following groups: (1) flow rates; (2) valve condition; (3) lateral slope; (4) lateral condition; and (5) wastewater material. A testing protocol developed through experimental design with respect to the failure-mode classifications is proposed to determine the lifecycles and maintenance intervals for different backwater valve models. The results may be used to create policies and recommend maintenance procedures to ensure an acceptable level of backwater valve function and to mitigate the occurrence of basement flooding events due to sewer surcharge.

This study assesses the advantages and limitations of developing design storms using the partial duration series exceedance-based (PDS-E) rainfall frequency model in comparison with the annual maximum series (AMS) model. Rainfall records were obtained from 21 rainfall gauges in Ontario. A procedure to develop the PDS-E was derived, addressing sensitivities to missing values, selection of thresholds, and quantile and confidence limit estimates. The reference values of 1-h duration and 2- and 5-year return period design rainfall intensities were 10% and 3% greater in PDS-E than in AMS data, on average, indicating the merits of using PDS-E data for exceedance-based modeling of frequent events. The PDS-E estimates of 1-h duration and 5-year return period events were 3.5% greater than AMS estimates. The use of the PDS-E method over the AMS method for developing design storms for stormwater infrastructure is recommended.

So far, few studies have focused on the concept of critical flow velocity rather than bed shear stress for incipient sediment motion. Moreover, few studies have focused on sediment mixtures (graded sediment) and shape rather than uniform sediment for incipient motion condition. Different experiments were conducted at a hydraulic laboratory at the University of Guilan in 2015 to determine hydraulic parameters on the incipient motion condition. The aim of this study is to conduct a comparison between uniform and graded sediments, and a comparison between round and angular sediments. Experiments included rounded uniform bed sediments of 5.17, 10.35, 14 and 20.7 mm, angular uniform sediment of 10.35 mm, and graded sediment. Results demonstrated that angular sediment has a higher critical shear velocity than rounded sediment for incipient motion. Results also showed that for a given bed sediment, although critical shield stress and relative roughness increased with the bed slope, the particle Froude number (based on critical velocity) decreased. In terms of the sediment mixture, the critical shear stress (V_c*) was higher for the graded sediment than for the three finer uniform sediment sizes. The finer fractions of the mixture have a higher particle Froude number than their corresponding uniform sediment value, while the coarser fractions of the mixture showed a lower stability than their corresponding uniform sediment value. Results demonstrated that the reduction in the particle Froude number was more evident in lower relative roughness conditions. The current study provides a clearer insight into the interaction between initial sediment transport and flow characteristic, especially particle Froude number for incipient motion in natural rivers where stream beds have different gravel size distribution.

The Kabul River Basin (KRB) is witnessing frequent flood and drought events that influence food production and distribution. The KRB is one of the world’s poorest regions regarding food security. Food security issues in the KRB include shifts in short-term climate cycles with significant river flow variations that result in inadequate water distribution. Due to the lack of hydro-infrastructure, low irrigation efficiency, and continuing wars, the Afghanistan portion of the KRB has experienced low agricultural land expansion opportunities for food production. This research assesses the relationship between flood mitigation, flow balances, and food production and, cumulatively, assesses the social and economic well-being of the population of the KRB. SWAT modeling and climate change (CCSM4) implications are utilized to assess how these relationships impact the social and economic well-being of the population in the KRB. The intricacies of transboundary exchange and cooperation indicate that the conservation of ~38% of the water volume would nearly double the low flows in the dry season and result in the retention of ~2B m³/y of water for agricultural developmental use. Results show that the peak flood flow routing in reservoirs on the Afghanistan side of the KRB would have a substantial positive impact on agricultural products and, therefore, food security. Water volume conservation has the potential to provide ~44% more arable land with water, allowing a ~51% increase in crop yield, provided that improved irrigation efficiency techniques are utilized.