In this paper, an optimization model has been developed for computing the optimum sizing of a combined structural flood control system. The combination of a dam and a levee has been considered in this study without losing the generality of approach for other structural combinations. Compared to the previous studies, this study uses less simplicity assumptions. For example the geometry of the river and the levee were considered with more details and the levee were considered non-symmetric along the river axis. The optimization problem formed a large-scale nonlinear model with the objective to maximize the expected annual net benefits of the developed system, to result the optimum design return period (i.e. design flood), as well as, the optimum size of the system components, such as dam height, spillway dimensions, and levee’s height and setback. The Tang-e-sorkh River and the flood control system (under study) in Shiraz, Iran, have been selected as a case study. The model solution proposed a combined dam and levee system, with a design return period of 1000 years.

This paper has paid to review one of the structural flood control methods (levees). In order to speed up the design of levees, an optimization method has been proposed in this paper which can be a good alternative for the usual design methods. The advantage of using optimization method is that one can reach the optimal option by solving model for one time (or several times for further analysis) and there is no need to review various single options. Benefit-cost analysis has been used to optimize the dimensions of levee containing height of it and it's distance from the river bank. Obtained optimization model is a non-linear one that has been solved by LINGO 12 software. In this study, proposed system of flood control in dry Maali Abad river (TangeSorkh) of Shiraz has been studied. According to this studies and the execution of model, 20-year return period flood had the highest annual net benefit and was selected as the design flood. The obtained values for the height of levee and it's setback are respectively 1.7 and 6.1 meters.

Levees are man-made embankments built to prevent the rivers from overflowing their banks. A levee is a naturally elongated ridge or artificially constructed fill or wall that regulates the water level. It is usually earthen and often parallel to a river course in its floodplain or along low-lying coastlines. The levee construction is a common and very old method of river flood control recently used considerably as an engineering operation to reduce or prevent the detrimental effects of floodwaters. It can be used either alone or together with other methods to minimize the floodwater damage. The engineered earthen levees have three general types: compact, semi-compact, and uncompact. The formers are usually and traditionally used in high property value, population and land use areas, or in controlled compaction, steep-sloped embankments utilized on good foundation conditions during construction. The semi-compact or uncompact levees are generally used in low value, poor foundation areas or those with high rainfall during the construction season. Compared to other floodwater control methods, levees are more efficient because they are not only quite cost-effective, but also provide more safety factors for slope stability. The artificial levees are aimed at preventing the adjoining countryside flooding and slowing the waterways' natural course changes to provide reliable shipping lanes for maritime commerce over time. In addition, they also confine the river flow causing higher and faster water flow. Levee construction materials should be coarse enough to withstand the erosion caused by the flowing water, their shear strength should be enough to satisfy the levee's slope stability, and they should be sufficiently impermeable. By other definition, they should also contain fine aggregates to prevent the extra seepage that has undesirable effects on the levee's slope stability; therefore, making specific arrangements to reduce repercussions deems necessary. Massive constructions that require large amounts of materials need to use the available on-site materials to reduce the transportation distance and hence, the project construction cost; using on-site materials is a significant advantage the levee construction enjoys. As mentioned before, since the levee construction needs both coarse-and fine-grained materials to reduce permeability, the best choice can be the coarse-grained soil containing clay; therefore, both GC (clayey gravel) and SC (clayey sand) soil types take priority over any other types. Hence, evaluating the amount of the soil fine aggregates and the effects of compaction percentage on the permeability coefficient and on other strength parameters to meet the economic, speed, and time requirements of the levee construction is quite important. This research studies the effects of compaction percentage and the amount of fine aggregates on the SC soil permeability and on the steady and unsteady seepage flow through levees. Accordingly, three levee samples A, B, and C (from Mehran River borrow area) with respectively 12. 8, 20, and 28. 4% fine aggregates and 60, 70, 85, and 100% compaction have been selected to carry out the permeability tests. The results of the tests with different compaction and fine aggregate percentages showed that an increase in each sample’ s compaction percentage (from 60 to 100, 70 to 100, and 85 to 100) decreased the permeability coefficient 25, 14. 3, and 8. 91 times, respectively. At every compaction percentage, sample A's permeability coefficient was 1. 2 times greater than the sample B and 1. 69 times greater than the sample C and greater than the sample B was 1. 41 times greater than the sample C. Next, using the numerical modeling, both the flow rate (in the steady state) and phreatic line (in the unsteady state) through the levee were studied with different compaction percentages and the results showed that in simulating the unsteady seepage through the levee, the phreatic line did not intersect the downstream slope and was significantly far from it. The results of this research can be used to either design or construction of levees; furthermore, it can be used to analyze the effect of the soil compaction percentage on permeability parameter during the levees’ construction.

Design of flood control systems are subjected to different kinds of uncertainties of hydrologic, hydraulic, geotechnical, and economic along, due to inherent behavior of flooding and random errors associated with measurement. The purpose of this paper is sensitivity analysis to determining the effect of uncertainties on the dimensions of design parameters.Therefore, using LINGO software a nonlinear optimization model based on risk analysis in both deterministic and probabilistic scheme have been developed for design of one of the most common structural flood control measure. In The probabilistic design , each of uncertainties once separately and once again all together are applied and Monte Carlo simulation for uncertainty analysis has been used. In this paper a reach in the Moali-abad river at north of Shiraz city, has been considered as case study. According to the results of probabilistic and deterministic models, the optimum return period equal to 20 years. Unlike the deterministic model that every output (design parameters) is single valued, stochastic model gives a range for each parameter that its value affected by the uncertainty imposed. The results show that applying the hydrologic uncertainty in the design is more efficient than economic uncertainty, and the economic one is more efficient than the hydraulic uncertainty. In the situation of limited time and budget, it has suggested that at least hydrologic uncertainty has been considered in design.

The man’s craving for water has inspired many civilizations to be formed near rivers. The social and economic destructive consequences of flood in human societies are considered undeniable facts. Today human trespasses on riversides and also vegetation destruction have caused increase in flood damages. These factors lead to be not only vital and financial damages, but also damages such as soil erosion in upstream and soil deposition in downstream. This research aims to decrease flood damages using structural methods as well as investigating and finding proper locations to construct protective levees in high risk areas via studying torrent area of riversides. In this research, the Genetic Algorithm (GA) are applied to maximize the benefit of flood control and also to minimize the cost of protective levees construction. Therefore, the fitness function of the research is defined to maximize net benefit of the project. The objective of the present paper is to evaluate this method for decreasing flood damages in the “Sarm” and “Khoor Abad” rivers, located in Qom province in Iran. The proper location and height of levees are defined whether the factor of “the level of saved losses to the region by constructing protective levees minus the cost of constructing protective levees” is maximized. The results indicate that by constructing protective levees the rate of damages reduces up to 99% in comparison with a non-constructed protective levees scenario.

Uncertainty analysis is an essential part of every project dealing with uncertain phenomena, therefore the policy -makers might face unexpected happenings that may delay, or at the extremes, cause complete failure of any projects. Uncertainty analysis is usually preformed in the framework of risk management. The Monte Carlo simulation method is used for integrated and simultaneous analysis of different combinations of uncertainties. This method is a powerful tool to study the various states of the outcomes of a system due to the uncertainties that have significant advantages such as considering all the uncertainties and the ability to show different aspects of the utility function. Existence of dependent random variables is quite common and likely in natural and engineered systems. In order to evaluate the need for correlation actions uncertainty, the design of flood control systems in terms of hydrological, hydraulic and economic uncertainties is discussed. In particular, design of levees that are one of the most common structural flood control, has been studied. In the developed nonlinear optimization model, uncertainty once without correlation and again by considering correlation was achieved. Models have been solved by LINGO-13 software. In the model without correlation, the height and other dimensions of levee is less than what the model with correlation predicts. The results indicated that ignoring the type and level of correlations between each uncertainty, combinations of the outputs of the system will provide results that are impossible in the real world and are somewhat far from reality.

Increasing encroachment on rivers along with climate change has increased major floods. Levees are considered the most important structures to protect river banks and floodplains from flooding due to their simplicity of structure, inexpensive materials, and ease of implementation. In this research, an attempt was made to introduce a new approach in geometric modeling, to develop mathematical relationships to calculate the volumes of levees based on different location of each scenario in the floodplain. Study scenarios supply the protection of three kilometers of the Chabahar-Zahedan arterial road and its widening, which is located in the floodplain of the Karvandar River in southeastern Iran. Hydraulic simulations implemented in HEC-RAS for the existing condition and 13 different scenarios with 13 unique topographies based on the new approach, and the rate of reduction of the flood zone and embankment volume of levees for each scenario calculated in ArcMap. Based on the results, changes in the volume of embankments in different scenarios did not correlate well with the flood zone area reduction. Due to the direct dependence of scouring and thus geometry and volumes of levees on flow velocity, by calculating the flow maximum velocity in the study interval, the dimensionless coefficients of maximum velocity in different scenarios were calculated and applied to the calculated volumes of levees. Thus, by this approach and using quadratic polynomial equations, the coefficient of determination (R2) increased from 0.35, 0.48 and 0.50 to acceptable values ​​of 0.88, 0.91 and 0.92, for floods with return periods of 50, 100 and 200 years, respectively, which indicate the high efficiency of the proposed approach and also increasing in R2 values with an increase in the flood return period. Moreover, results show that the computational accuracy of regression relationships in the scenarios with levee locations in the middle distances from the road axis is higher than other scenarios which are closer or farther. This result is due to more irregular river geometry in the scenarios closer to the road and the intensification of nonlinear changes in flood parameters in the farther scenarios.

The present study is aimed to optimum design the one of the structural methods of flood control (Levees) based on dynamic programming (DP). In order to accelerate computing time, a model was created based on the combination of discrete differential dynamic programming and genetic algorithm (GA-DDDP). The objective function of this model is to minimize the total costs, including the cost of constructing the structure and residual damage cost. For this purpose, the length of the studied river was divided into three reaches and the optimal dimensions of the four sections were obtained as output results. Modeling and running was done by coding in MATLAB software and the results showed that the running time of GA-DDDP combined model is just 11% of the time to running the classic dynamic planning model. Also in this study, the results of the four-section model were compared with the simpler single-section model (equivalent section). The results show that the simplification of model to one section causes the increasing costs to about 20%.

flood control is one of the important requirements in development projects of major water resources. In this regard, the main purpose is to reduce or eliminate the economic, social and environmental damages that are caused by floods. On the other hand, many irrigation and drainage networks are in the vicinity of the rivers and, therefore, the occurrence of floods can cause irreparable damage to the land and network structure. Embankment failure due to water overtopping during floods is a common phenomenon which brings great financial losses, human casualties and environmental damages. Therefore, this research was aimed at investigating the mechanism as well as the effective variables on embankment failures...

A site evaluation was made for a low-lying property in an old river levee/marsh association, used marginally for cattle raising, which was contaminated due to historical practices. Contamination was related to geomorphology: the lowest areas contained 79 % of the contaminated samples. Other contaminated samples were all rear access roads (probable intentional dumping). There were no samples in the higher, levee areas away from roads with hydrocarbon concentrations above 3,000 mg/kg. Medium and high impact levels, corresponding to average hydrocarbon concentrations of 13,400 mg/kg and 109,700 mg/kg, respectively, were found in 28 % and 27 % of the property area. The medium impact level was predicted to have a reduced pasture production potential of ~ 50 % while at the high impact level practically no pasture production was predicted. Toxicological risk to cattle is present in only 12 % of the sample points although almost all of these are in very marshy areas not apt for cattle raising. Because the hydrocarbons at this tropical site are very weathered, acute toxicity was not related to hydrocarbon concentration. Although slightly more than half of the property has hydrocarbon concentrations above the permissible limit, only about one-third of the contaminated area is apt for cattle raising. This study, based on hydrocarbon distribution related to site geomorphology, soil toxicity bioassay, risk assessment to cattle and evaluation of pasture production allowed to made a more accurate assessment and definition of future use of the site. These criteria could be used for diagnostic studies of sites with similar tropical conditions.