Understanding the process of securing the city of Rasht in order to deal with natural hazards (floods and inundation)

Academic thesis for obtaining a master's degree

Department: Natural geography orientation: Climatology

Abstract

Flood is one of the phenomena in nature that mankind has witnessed since long ago. In Iran, due to the large area, multiple climates and temporal and spatial density of rainfall in most watersheds, every year we see huge floods in most regions of the country. The city of Rasht is not exempted from this natural phenomenon and there have been many destructive floods in the past few years. The security process includes all kinds of measures that are taken before the accident to control and reduce the possible loss of life and money caused by the flood. It is necessary to pay attention to these methods due to the inadequacy of physical methods. In this research, the rainfall statistics of the last 30 years in Shahr-Rasht station were extracted, then the rainfall status and the possibility of flooding, as well as the volume of runoff caused by rainfall in the legal limits of the city, the total area of ??the basin, the place of concentration and the direction of the flow of wastewater from the rainfall around this city were determined using the geographic information system. The research method is descriptive-analytical and management and operational measures can be mentioned according to the practical model of immunization.

Keyword: Flood management, urban flooding, immunization, Rasht city

Introduction

Previously, it was thought that the occurrence of natural disasters in urban areas has less effects and consequences compared to rural areas. But today, due to the specific changes that have occurred in the structure and organization of cities, it has made them very vulnerable to unexpected events (Asgari, 2012: 49). A flood is a sudden event that many factors are involved in its occurrence. These factors can be generally classified into three main groups: climate, regional and basin characteristics, and human activities. The surface areas of Rasht city are among the areas that sometimes suffer from floods. Among others, we can mention the floods of 1969 and recent years. According to the collected statistics and information, one of the most important reasons for the aggravation of flood damage in Rasht in recent years is the destruction of vegetation, the construction of inappropriate structures, unauthorized encroachment and occupation of the river, and lack of attention to advance knowledge and flood forecasting and warning systems. Since the study area contains a large population, the experiences of past events have proven that planning and preparing for a crisis has a great impact on reducing damages. On the other hand, according to Article 1 of the Law on Prevention and Combating Flood Hazards approved on 9/2/1343, in order to protect people's lives and property from floods, the Ministry of Interior is obliged to carry out the urban security process to deal with floods. (Sahibqarani, 1371). One of the important measures to prepare for the crisis caused by the flood is to pay attention to education and culture. In principle, it can be said that the success of other activities related to crisis management depends on foreknowledge (Habibi, 2008).

Immunization process includes all kinds of actions that are carried out before the incident to control and reduce the possible loss of life and money caused by floods. One of the most important security methods can be mentioned the managerial and operational measures.

The purpose of this study is to identify the points of accumulation of runoff in the city and reduce the problems and dissatisfaction of the people due to this, collect the surface water of the roads and transfer it to the main drainage network in order to protect the roads and roads from destruction caused by the increase of water and floods and reduce the interruption and slowness of traffic, reduce the costs of cleaning and collecting surface water during rains, improve and increase the beauty and pleasantness of the environment urban areas, transferring water from problem areas to water-receiving areas, reducing the possibility of flooding in high-risk areas, following the future development of the city from the proposed drainage situation, securing more residential, commercial and service areas, reducing the costs imposed on private individuals and government organizations, increasing people's cooperation with the municipality and other relevant departments as a result of observing the favorable effects of project implementation, facilitating the estimation of hydrological calculations related to the city such as discharge from the city surface, preparing the ground for better use of runoff from the city for sewage treatment, water transfer For agriculture and industrial purposes, it is better to preserve the agricultural and agricultural lands on the edge of the city from the risk of waterlogging and flooding, as well as to prevent these lands from becoming stagnant.

Chapter One

Research Overview

Introduction

Problem Statement

Research Question

Research Objectives

Research Hypothesis

Research Method

Information Collection Method

Information Collection Tool

Introduction

Natural Disasters They always affect the planet and cause harm to people such as injury, malnutrition, mental stress and death. Earthquakes and floods are considered as the most important natural disasters in our country, and what makes these disasters a disaster is the lack of awareness to deal with their consequences and prevent the impact of natural disasters on health-economic and environmental pillars. The word "flood" means overflowing water, submerging an area of ??land and becoming a storm. Basically, the magnitude of floods and their repetition over time depends on the intensity of rainfall, the permeability of the land and the topography of the region. Heavy rain, melting snow, changing riverbeds and destruction of dams and dams are among the factors that may cause floods. Urban constructions and removal of plants reduce the amount of infiltrated water and increase the surface water. On the one hand, the large volume of water increases the magnitude of the flood, and on the other hand, with the increase in erosion, it creates sediments, which, by leaving them, reduce the capacity of the main river bed. The above usually have a gradual effect, but sudden and catastrophic floods are often caused by the destruction of dams and dams. In Iran, although rainfall is low in many places, in most areas, 60% of the annual rainfall may occur in one night. This factor, together with the steep mountain slopes of Alborz and Zagros - which place our cities in their range - has caused flooding to be one of the concerns of some people - almost in all seasons of the year. Floods in Iran are very polluted due to geological features and environmental destruction and bring a lot of mud. For this reason, most floods in Iran cause a lot of damage. Floods cost the national economy 200 million tomans a day. According to one of the reports of the National Disaster Preparedness and Control Plan, Iran has faced 967 floods in the past 25 years, of which 117 were very important and caused a lot of damage and casualties. During these years, with an average of 39 floods per year, 916 billion and 200 million Tomans have been damaged in the country, and the average annual damage was 36 billion and 600 million Tomans. During the last 25 years (from 1351 to 1375), 42.5 million people of the country have been affected by floods. During this period, 2 million 892 thousand 400 people became homeless and an average of 500 residential units were destroyed or damaged every year. In another report of the country's unexpected events headquarters, it is stated that only in 1370, 61 floods and 27 earthquakes occurred in the country. Building houses in the river banks, that too with inappropriate materials, has been the main cause of flood damage in many cities of the country. In the cities of many countries that have similar conditions with us in terms of the presence of rivers, many houses are built on the banks of the rivers due to the high value of the land or to take advantage of the beauty of the river, but delicate expert measures are also used to predict the risks of flooding. Often, in such cities, basement construction permits are never granted. Houses are built in such a way that water can easily pass through the infrastructure. Permitting the construction of basements in buildings that are built near the road or the banks of rivers, excessive development of the city which destroys its permeability due to the change of the land cover, narrowing the channels and important routes of the cities, concreting them that increases the acceleration of water, pumping water to high altitudes that are sensitive to landslides, and so on. . . Among the management mistakes that municipalities and city managers should not commit. In Gilan province, due to heavy rainfall and lack of proper planning by the city officials, this problem is more observed. In fact, after every rainfall, most of the small and big cities of the province suffer from dangers such as floods and inundation, and in the meantime, the city of Rasht is very vulnerable to any heavy rainfall and the roads are blocked in most of its streets, causing many problems for the residents of this city.