Academic Thesis for Master Degree
Department of Natural Geography, Climatology in Environmental Planning
Abstract
Nowadays, the technology has reached the level of perfection to prevent the occurrence of harmful floods and change the factors of atmospheric elements. It should be searched on the ground, especially in the area of ??watersheds. In this regard, the first measure that is proposed to reduce the risk of flood is to control the flood at its source, i.e. under the watersheds. In this regard, the identification of flood-prone areas within the watershed should be more important, so the areas with high potential in flood production should be identified in order to provide the possibility of optimizing the operation or business at a smaller and less dangerous level. Flood control plans will be prevented. The purpose of this research is also to present an alternative method, by using it, it is possible to consider the mutual effects of effective factors on landslides, and determine the dangerous areas of landslides in the basin. In this research, an attempt has been made to introduce one of the methods of flood zoning using the integration of ARCVIEW and HEC-RAS software and the HEC-GeoRAS-431 add-on, while flood zoning in the Murghak river, the newest, most economical and shortest flood zoning method in terms of economy and time is introduced, its advantages and capabilities are examined. Also, sections of the river have been identified that have the largest flood width and extent with a return period of 25 years. These sections downstream of the river include the distance between the main road from Foman to Punel to the end of the river (entrance to the Anzali lagoon) in the last 8 km of the total of about 30 km of the river.
Key words: flood zoning, HEC-RAS hydraulic model, HEC-GeoRAS-431 extension. They are located near rivers. These structures mostly do not have maps to determine the flood extent. Meanwhile, one of the basic and important information in the studies of construction plans in the world is the use of flood zoning maps in the flood management studies of the plain. Before any investment or the implementation of development plans, the investigation and determination of flood-prone and high-risk areas in the rivers are on the agenda of relevant organizations (especially regional water companies). This will prevent irreparable damages from damaging floods to the facilities and structures built on the banks of the rivers. At present, the technology has reached the level of perfection to prevent the occurrence of such harmful events and prevent the occurrence of adverse events. Therefore, any effective solution should be sought on the ground, especially in the area of ??watersheds. In this regard, the first measure that is proposed to reduce the risk of flood is to control the flood at its source, i.e. below the watersheds. In this regard, the identification of flood-prone areas within the watershed should be more important, because due to the large size and extent of the watersheds, flood control and flood control are essential. The reservoirs cannot be accommodated and even in the case of lack of accuracy, it can intensify and cause a simultaneous change in the prices and islands of the basins. It is necessary to identify the areas that have a high potential in producing floods, so that the possibility of optimizing operations or business at a smaller and less dangerous level can be provided, and the additional costs of flood control plans can be prevented.
The aim of this research is also to present a reliable method, by using it, we can also consider the interaction effects of effective factors on flooding, and determine the dangerous areas of the floodplain in the basin. Flooding means the potential to produce floods in the sub-basins from the point of view of the impact and participation in flood characteristics. (level, flow, or width) of the basins. In other words, it means flooding, the separation of the hydrological reaction of the basin and the effect of the flood load in relation to the contribution of the sub-basin. The flood will be more in that sub-basin, but the sub-basins that have a more effective contribution to the flood characteristics in the output hydrograph of the main basin are more flood-prone than other sub-basins, as well as the flood index, which is an expression of the hydrodynamic effect produced on the surface of the sub-basins. (considering all the features of the sub-basins) in the increase or decrease of the flood characteristics of the basin, which can be measured by the water level, discharge, and flood zone for the participation of the sub-basin in the basin's outflow. In this study, an attempt has been made to introduce one of the flood zoning methods using the integration of ARCVIEW and HEC-RAS and HEC-GEORAS software, while zoning the flood in the central part of the Murgak river, the newest, most economical and shortest flood zoning method in terms of economy and time has been introduced, and its advantages and capabilities are examined.
1-2.Problem statement
Marghak is one of the permanent rivers in Fomanat study area and in Masal city of Gilan province, which plays a decisive role in the economy of the region. Determining the boundary and bed of this river is one of the main concerns of regional water companies and other related organizations. The presence of paddy fields, fish breeding ponds, industrial and agricultural facilities, and residential and commercial places in the boundaries of this river has made identifying its legal boundaries difficult. Also, illegal occupations by profiteers on the banks of the river cause many problems. One of the most important tasks in this field is determining the boundaries and extent of flooding along the riverbank, which prevents any kind of misuse.
1-3. Research objectives
- Identifying the capabilities of HEC-GeoRAS software in zoning the flood-prone areas along the Murgak river
- Identifying the flood-prone areas in the sections of the river in the discharges with different return periods
- Providing the necessary solutions to deal with the floods that occurred, especially in the sections of the river that are located in urban areas.
1-4. Research question
Does GIS software have the ability to create flood zoning maps with different return periods using mapped data?
1-5. Research Hypotheses
According to the objectives and the main question of the research, the following hypotheses are discussed and in this research, an attempt is made to discuss the hypotheses.
GIS software can create flood zoning maps.
These maps have the ability to identify high-risk areas.
The results of this research are consistent with the facts of the floods that occurred in the catchment area.
1-6. Research limitations and obstacles
Researchers always face limitations in their research. Limitations, as a fact, slow down the achievement of any goal, the present research is no exception to this rule. Therefore, the main limitations of this research are:
1 - Problems caused by field visits to Marghak River to control the harvested points as a result of field operations
2 - Lack of resources regarding the scope of the research
3 - Insufficient cooperation of the custodian organizations and lack of up-to-date information in this field.
1-7. Research steps
Firstly, using the mapped data of the area obtained in the boundary and bed determination project, including river plan maps with a scale of 1:2000, bed conditions, such as the main line of the river flow, sides and transverse sections and so on. The geometric data required to perform the simulation is determined (from the TIN map) Figure 3-4, then the data is entered into the HEC-RAS model. After that, flow data and boundary conditions are entered into the system and hydraulic calculations are performed.
The results are prepared in the form of input formats to the GIS environment, and in this environment, using the HEC-GeoRas431 add-on, the necessary processing is done, and finally, maps of water depth, water velocity, shear stress, and flow strength are created along the river span. These maps are transferred to Google Earth environment for better display. These maps accurately show the flood area with different return periods, and also show the sections of the river where the flood spreads and causes flooding, along with the depth of the flooding.
Determining the flood zones for floods in certain return periods is called flood zoning (Ministry of Energy, 1384). In other words, flood zoning is the determination of the extent of flood progress, its height and characteristics in different return periods. In flood zoning, it is aimed at that all the areas around Wasilab Dashta Airport should be divided into parts with different risks for the purpose of controlling land use and development, to be used in determining land use, identifying areas in flood insurance, and creating mandatory restrictions in high-risk areas.
Generally, flood zoning can be described as follows: Determining areas within the flood plain that are suitable for various land uses, including recreational spaces, agriculture, industrial areas, and similar uses. These areas are usually vulnerable to floods. All areas of Badas are divided into parts with different vulnerability in order to control users and development. Zoning can be used to specify and clarify the level of vulnerability to floods for potential users, identify areas for flood insurance, and create mandatory user restrictions in vulnerable areas.