**1. Introduction**

Every construction project, regardless of size, scope, complexity, nature, or location, has unique risks. Failure to manage relevant projects correctly also increases the risk and causes losses to the balance sheet. It should be emphasized that a risk, even

if small, in the project may create uncertainties during the implementation phase and lead to negative consequences that may affect the success of the project. Additionally, new risks may arise at different stages of a project. However, it is clear that high risks waste resources, increase project costs, reduce efficiency, and extend project completion time. Therefore, it is of great importance to correctly identify and manage risks at every stage of the project. Risk definitions are of greater importance in the management of water resource structures such as dams and storage facilities, which are built for public service purposes and are vital for living life downstream.

Although dams provide benefits such as domestic and industrial water supply, electrical energy production, and agricultural irrigation, they may cause some environmental impacts. These affect communities through resettlement and other socio-economic impacts, result in environmental concerns, and create sedimentation problems in the long term. In addition to all the negative consequences, if they collapse, they can cause major disasters resulting in great loss of life and property. These problems and concerns need to be alleviated through proper planning and incorporating various improvement techniques according to the demands of society. Hariri-Ardebeli [1] suggests that these expectations can be most effectively met by implementing systematic risk management that includes factors such as sustainability and public participation during dam planning, construction, and operation stages.

According to 2016 data in the USA, there are over 90,000 small or large dams and approximately 18% of them are defined as high-hazard dams. It has also been observed that the average lifespan of dams is over 50 years. It has been stated that at least 64 billion dollars are needed to meet the current safety requirements of these dams across the country [1]. The number of large dams in Turkey is close to 1500 and their average age exceeds 30 years. These dams have costs of up to 10 billion dollars for changing physical conditions and updated safety requirements. Significant damage occurred in 40 dams by two major earthquakes (Mw7.8 and Mw7.6) on February 06, 2023 [2, 3] and the cost of the damage to these dams was determined as 4.0 billion dollars [4]. All these developments necessitate the effective use of water resources for social life (water and food safety as well as the danger of downstream life), and the need for all risks (especially during the operation phase) to be well identified and managed effectively.

Safety concern for a dam structure is mainly affected by ground motion and result in loss of stability and some physical defects in the structure [5]. Pre-planning for dams and earthquake mitigation generally uses simplified procedures. An assessment of the overall stability of the structure should be included. Simplified procedures are generally used for pre-planning earth-rockfill dams. The analysis of concrete dams exposed to earthquakes must include an assessment of the stability of the entire structure to withstand lateral forces and moments [6, 7]. Various methods from simplified analysis to sophisticated techniques are used to analyze seismic loads acting on concrete structures. It should be noted that seismic analysis is the first step in determining the overall risk of a dam structure.

This chapter considers a portfolio of dams on two tributaries of the main river of Euphrates Basin. The main River, with its tributaries of Murat, Perisuyu, and Karasu has a 2800 km length. It flows through Iraq into the Gulf in the south. The flows upstream and on the Syrian border are 650 cubic meters per second and 950 cubic meters per second, respectively. Within the basin, 40 large dams are constructed to use the basin's energy and irrigation potential. This article assesses the overall risk of 11 large dams in the two Euphrates River cascade systems. In other words, this study summarizes the safety of dam structures during the operational phase, especially


**Table 1.**

*Characteristics of large dams on two tributaries of Euphrates [8].*

*Risk Management of Large Dams under Operation Stage and Case Studies for Cascade System DOI: http://dx.doi.org/10.5772/intechopen.113342*

with regard to the risks to life downstream, highlights the methods used for the overall risks of the structures involved, and highlights the risks posed by dams.

The author discusses individual structures and cascading structures in the country's largest watershed. **Table 1** introduces the general characteristics of dams. This paper refers to some studies done previously [9–11]. The author and his co-workers have completed many international and national projects about dam safety and risk management of earth structures relating to water resources and introduced a lot of studies in congress, symposium, and journals. These studies mainly concentrate on dam safety concepts in majoring and risk management of dams and their appurtenant structures in minoring [12–28].
