This research examined the influences of outflow characteristics affecting riverbank stability. The 130-km stretch of the Lower Osage River downstream from Bagnell Dam (Missouri, USA) provided an excellent case study for this purpose. The integrated BSTEM model with the HEC-RAS model was accurately calibrated and validated with data from the US Geological Survey. Then, the outflow characteristics (peak flow duration, flow drawdown rate, and low flow duration) were investigated individually. The results of this study showed that: (1) riverbank stability is little affected by the duration time of the peak flow, especially on the reaches far from the dam; (2) sudden flow drawdown significantly reduces riverbank stability; however, the impact of the drawdown rate decreases with distance from the dam; and (3) the duration of the low flow after peak flow influences the riverbank stability value proportional to the distance from the dam. The time of low flow before failure increases as the distance from the dam increases.

The study of flood risks has a fundamental role in ensuring the safety of cities near rivers and drawing up plans to protect them during future floods. This study aims to manage potential flood risks, and Tikrit city was used as a case study. The daily discharge of the Tigris River in the study area was provided by the Iraqi Ministry of Water Resources from 2019 to 2022. The HEC-RAS software was utilized to build a 2-D flood model to simulate potential flood scenarios. First, the model was calibrated by adjusting the value of Manning's coefficient (n), and it was found that n = 0.031 reflects the nature of the region because the Nash-Sutcliff Error (NSE) was 0.93. Then, the efficiency of the 2-D flood model was verified by comparing the model’s results with the study area’s satellite images, and the results showed a great match. Following that, the 2-D model was used under different flooding scenarios. The results showed that the size of areas exposed to flooding increased with the discharges passing through the Tigris River. For instance, increasing the discharge to 800m3/s increased the flooded areas by 13.7%, while increasing the discharge to 1500 m3/s increased the flooded areas by 90.7 % compared to the river’s normal flow. Also, the results showed that the eastern regions of the riverbanks are more vulnerable to flooding than the western side because the ground levels are low on the eastern side compared to the western part of the riverbanks.

The fluctuation of water level downstream from dams due to hydropower flow releases can negatively affect riverbank stability. This research aims to investigate riverbank instability resulting from the outflow variation of hydropower plants, using Bagnell Dam and the lower Osage River (Missouri, USA) as the basis of analysis. The effects of the water releases from the Bagnell Dam were investigated by computing a series of safety factors in relation to outflow events for 78 cross sections along the 130-km stretch of the lower Osage River using the BSTEM algorithm integrated into the HEC-RAS model package. The results showed that the rate of change in the flow magnitude at each cross section impacts the calculated safety factor. The flow release fluctuations will change the value of the safety factor along the river over time, as the safety factor value closely follows the variation in the flow rate. Also, the results show that the cross sections closer to Bagnell Dam are subjected to be more unstable than those farther downstream of Osage River.

The flood risk management is one of the primary concerns in water resources engineering. The flood occurs as a result of unexpected events in the hydrological cycle, such as rainfall in the upstream tributaries of the rivers. However, engineers have to have a precise tool to manage the risk of flood. Nowadays and due to the tremendous revolution in computers, which helps to build a credible mathematical models, management of flood become doable. In fact, expressive which model should be used is the challenge. This paper aims to review several hydraulics models that used in flood risk management.