Concept of flood disasters
Flood disaster refers to the phenomenon of flooding and waterlogging
in low-lying areas caused by heavy rain, heavy rain or continuous
rainfall.Waterlogging mainly harms the growth of crops, causes crop
reduction or failure, and destroys the normal development of agricultural
production and other industries.The impact is comprehensive, it will
also endanger the safety of people's lives and property, and affect
the long-term stability of the country.
Two necessary conditions for disaster formation:
(1)Natural Conditions: flood is the direct cause of flood disasters.
Disasters may occur only when the natural variation intensity of flood
reaches a certain standard.The main influencing factors are geographical
location, climatic conditions and topography.
(2) Socio-economic conditions: only when floods occur in places where
human activities occur can they cause disasters.The areas most
threatened by floods are usually the middle and lower reaches of rivers,
which are often economically developed due to their abundant water
resources, flat land.The threat of flood disaster will restrict the social
and economic development and affect the safety of people's lives and
Types of flood disasters
Floods can be divided into river floods, lake floods, storm surge floods
and so on. Among them, river floods can be divided into the following
types according to their causes:
(1) Rainstorm flood: the most common and threatening flood, which is
formed by heavy rainfall, also referred to as rainwater.
(2)Mountain torrent: it is a flood that rises and falls sharply in
rivers.Mountain torrents are characterized by sudden, concentrated
rainfall and strong destructive force, often accompanied by debris
flows,landslides,collapse and other disasters.
(3)Snow-melting floods: mainly occur in high-latitude snow-covered
areas or mountain snow-covered areas.
(4)Ice flood: often occurs in the Yellow River, Songhua River and
other northern rivers.Due to a river section in the river flows from
low dimension to high latitude, when the temperature rises, the upstream
of the low latitude reaches thaws first, while the high latitude reaches
are still frozen, the upstream water and ice accumulate in the downstream
riverbed, forming ice dams, causing flooding;in addition, ice floods
may occur when rivers are frozen.
(5)Dam-break floods: floods caused by sudden break or collapse of dams
In addition, waterlogging can be divided into waterlogging and
“closed-door waterlogging”.Waterlogging refers to excessive rainfall
that cannot be discharged from rivers and causes waterlogging.
“Closed-door waterlogging”refers to the regional waterlogging disaster
caused by the high river water, which makes the lakes and depressions
in the lower reaches of the tributaries unable to discharge water.
Reasons for frequent floods in China
This is closely related to China's climate and geographical conditions.
China is located in the southeastern part of Eurasia, bordering on the
Pacific Ocean to the east, spanning three latitudes: high, medium and
low with obvious monsoon climate characteristics. In summer, the south
wind blows and the air is humid,the rainfall mostly concentrates in summer,
and mostly occurs in the form of rainstorm with high intensity.Not enough
space on the ground to disperse or store the water in a short period of
time which result in flooding.At the same time, the abnormal climate in
recent years and unreasonable human production activities,blind reclamation
and deforestation, sediment deposition in rivers and lakes, and land
reclamation,which are also the causes of floods.
Temporal and spatial distribution of flood disasters
Floods are often distributed in densely populated areas with high
agricultural reclamation, concentrated rivers and lakes, and abundant
rainfall,such as, warm temperate zone and subtropical zone in the
northern hemisphere. China and Bangladesh are the places with the most
frequent flooding disasters in the world,also serious in the United
States, Japan, India and Europe.According to historical statistics,
the most serious flooding areas in China are mainly the southeast coastal
areas, Hunan-Jiangxi areas and Huaihe River Basin,the secondary flood
areas are the middle and lower reaches of the Yangtze River, Nanling,
Wuyishan areas, Haihe and the lower reaches of the Yellow River, Sichuan
Basin, Liaohe River and Songhua River areas.The northwest, Inner Mongolia
and Qinghai-Tibet Plateau are the least flooded areas in China, followed
by the Loess Plateau, Yunnan-Guizhou Plateau and Northeast China.Generally
speaking, the general characteristics of flood distribution are more in
the east and less in the west, more coastal areas and less inland areas,
more plain lakes and less plateau mountainous areas, more mountains in
the east and south, less in the west and north.
Harm of flood disasters
Floods and waterlogging disasters occur frequently, spread widely, come
with ferocious force and great destructiveness, which not only flooded
houses, caused a large number of casualties, but also took away all the
goods in the residential areas, including grain, flooded farmland, destroyed
crops, resulting in a substantial reduction in food production, then lead
to famine.Floods can also damage factories, communications and transportation
facilities, causing damage to various sectors of the national economy.Since
the 21st century, great floodshave occurred in various countries of the world,
resulting in the deaths of tens of thousands of people and the displacement
of millions of people.
Flood disaster prevention measures include engineering measures
and non-engineering measures.
(1) Flood control engineering measures: including river embankments,
reservoirs,flooddiversion projects,flood storage,detention areas and
river regulation projects.Strengthening embankments, strengthening
embankment construction, river regulation and reservoir engineering
construction are the direct measures to avoid flood disasters.
Flood control project is a long-term and arduous task, according to the
natural and geographical conditions of the river basin, carry outcomprehensive
harnessing, build embankments,renovate river courses, and engineering
measures of storage, discharge, stagnation and grading should be taken
reasonably.Build dikes along rivers to protect both sides from flooding,
at the same time, measures such as river channel clearing and silting,
and manual cutting and straightening are adopted to increase the flood
discharge capacity of the reach.In the vicinity of key protected objects,
flood diversion works of rivers should be built, flood storage and detention
zones should be established, and joint use of rivers and dikes should be
coordinated to ensure the safety of protected objects.
Cities should focus on strengthening protection, improve flood control standards
for embankments along rivers and large and medium-sized cities, and strengthen
and raise embankments to meet the once-in-a-century standard, so as to meet
the needs of urban economic development.
(2)Non-engineering measures: mainly through the restoration of vegetation
to improve the climate and environment, do well in water and soil conservation.
Afforestation, such as closing mountains to plant trees and returning farmland
to forests, etc, also can promote the soil to absorb more water and weaken the
direct erosion of the ground by rainstorm.Prevent soil erosion, avoid silting
up lakes and rivers in the lower reaches, and ensure the discharge capacity of
rivers and the flood storage function of lakes.Long-term and sustained implementation
of soil and water conservation can fundamentally reduce the chances of flooding.
Self-rescue methods for flood disasters
(1) When a flood arrives, those who are too late to transfer should quickly move
to hillsides, highlands, buildings, flood shelters and other places nearby,
or immediately climb up roofs, high-rise buildings, big trees, high walls
and other places for temporary shelter.
(2) If floods continue to rise and temporary shelters are difficult to protect
themselves, they should make full use of the life-saving equipment prepared
to escape, or quickly find some door panels, tables and chairs, wooden beds,
large pieces of foam plastic and other floating materials to form rafts to escape.
(3) If surrounded by floods,try to contact the local government flood control
department as soon as possible, report our position and danger, and actively
Note: Never swim to escape, do not climb electrified poles, iron towers,
or to the roof of mud houses.
(4) If a person is involved in a flood, he or she must seize as much as possible
the fixed or floating things to find an opportunity to escape.
(5) When the high-voltage iron tower tilts or the wire ends droop, must be quickly
avoided to prevent electric shock.
(6) After the flood, we should do well in hygiene and epidemic prevention
to prevent the epidemic.