Flood control methods Structural measuresMohammad Reza

The following sample essay on flood control methods; Structural measures

Mohammad Reza Ghaemdoust

Abstract

Regarding that flood risks threaten the lives of many humans, today’s understanding with such dangers and damages caused by it, as well as evaluation and coping with strategies, are those of great importance in urban management systems. Basically complete control and containment of flood is practically impossible due to physical and economic inability, except for some cases. Therefore, the concept of flood control in practice is reducing flood damage and defined as any method, activity and action taken to decrease the negative effects and impacts of flood to protect shores, human and their property, land and facilities adjacent to the rivers, and generally flood plains.

Usually economic, social, environmental issues, technical abilities, and the conditions of the area are effective in choosing flood control methods. In this studyStructural solutions are provided to reduce the vulnerability of the phenomenon and control it. Keywords: flood, flood dangers, structural solution, flood damages

Introduction

In Iran, based on natural geography and incident rate, in some areas, in some cases, the effects of flood damage are not less than earthquake, and lack of stopping from occurring can result in irreparable physical and financial losses.

In general, the flood is severe during rain or snow in a particular geographic region that causes river bed change and demolition of dams and waterways. Although Iran has dry climate in comparison with other countries, normally, the rainfall is about 651 mm per year.But rainfall in some parts of the country is rapid and fast and taking into account the drought of nature, after a rain, there is an instantaneous flow of water and the intensity of precipitation causes flood to damagehuge amount of people’s agricultural and financial resources.

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Addressing flood mitigation, as far as possible is one of the unstoppable measures. These actions are divided into three structural, non-structural, and combined categories. Structural method refers to all activities that by constructing engineering structures, trying to reduce peak flood, increasing river capacity and preventing river flooding and transferring and directing excess water to other areas, thereby reducing flood damage. These methods, known as flood control hardware, are commonly used before flooding. In this paper, we have tried to design structural methods for flood control in order to reduce the flood intensity and its damages.

Structural measures of flood control

In structural methods, the goal is to reduce flood and is based on physical protection by structures. These methods are applied before the occurrence of the floods and they are mainly used to prevent flooding. The river is organized with the aim of increasing the flow capacity and reducing the water level in order to protect the river itself and the flood area. Includes the following. Structures extended along from an angle with the water flow to part of the river’s width. These lateral walls, sometimes as a series of sequential and sometimes isolated, cause deviation of water from the location of the edges and direct it towards the middle of the rivers. Mainly in controlling erosion and protection of rivers, especially in the protection of the outer walls, route correction schemes and river widths are widely used.

These structures affect the flow direction and cause a change in the flow pattern of the river and the deviation of the flow from the erosional walls to the middle of the river. In order to protect the river’s surrounding lands against flood, a structure that is usually constructed in parallel with the river route is used. These walls hold the flood and prevent flood penetration into adjacent lands. These walls are made of building materials, stone, concrete or even reinforced concrete and should be designed against the forces involved.

Diversion channels are usually designed to transfer excess discharge to the river carrying capacity at critical points. Often, these channels begins in the upstream of the towns and after turning around the city at the right place, they come back to the river or may even be into another bigger river ora reservoir.Flood diversion of rivers is one of the best methods of flood control that generates overall flood control and avoids the risk of it from the river system. By the construction of a reservoir, excess water is stored for dehydration and prevented from running in the stream and creating flood.

Dam reservoir in addition to reducing peak flood can act as a delayed structure, widening the flood hydrograph and expanding its runoff with higher safety. Retarding basins or open dams are small dams only designed for flood control purposes. While the outlet of the reservoir dams is equipped with valves, the output of the retarding basins is uncontrolled and without valves. Automatic discharge is done according to the amount of water on the drainer. The use of several retarding reservoir can also be commonly used and may be economically and considerably more than one with high altitude.

Any type of operation to concentrate and extend decentralizedwater in order to improve the status of water and soil, vegetation, nourishment of underground aquifers, and prevents any waste of water is called flood spreading. In this way, by creating additional facilities, it is tried to either reduce the speed of water or increase the level of water in contact with the ground. This method is applicable when undergroundwater resources are free-flowing aquifers and the permeability of unsaturated layers and in particular the surface layers of the soil is relatively high. The advantages of this method are easily applied and simple calculations, the use of local construction facilities,thelack of need for special materials and experts, and cheapness.

Recharge wells are like pumping wells. In this method, by drilling the injection wells, surface water is sent to the wells and feed groundwater aquifers. In this method, in addition to the diversion facilities, transfer and sedimentation, several injection wells are needed that will increase the price of the project. But in areas where the price of land is high or there is not enough space this method can be used. In areas where the groundwater level is adjacent to the river bed, there is no possibility of penetration of the river water into the aquifer. In this situation, required space for penetration of water should be provided by a specific method. In this method, pumping water from underground aquifers and transferring them to another location will provide space for water penetration. Actually the lowering of the water level around the well causes the hydraulic gradient to escalate between the river and the well, and more water enters the river.

Conclusion

In this article, a relatively complete review of the flood control structural measures carried out. In accordance with the research presented, structural methods in order to control, reduce and confront to flood damage were discussed. Depending on the rainfall rate, the fertility of the land, geographical location, importance, availability of facilities, one or a setof these methods can beused. Knowing all kinds of these structural methods and familiarizing them with each other,while expressing the characteristics of eachone, can greatly help experts in choosing the right method.