flood
A flood is an overflow of water that submerges land.[1] The European Union (EU) Floods Directive defines a flood as a covering by water of land not normally covered by water.[2] In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries,[3] or may be due to accumulation of rainwater on saturated ground in an areal flood. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area. Floods can also occur in rivers, when flow exceeds the capacity of the river channel, particularly at bends or meanders. Floods often cause damage to homes and businesses if they are placed in natural flood plains of rivers. While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and commerce by being near water. That humans continue to inhabit areas threatened by flood damage is evidence that the perceived value of living near the water exceeds the cost of repeated periodic flooding. The word "flood" comes from the Old English flod, a word common to Germanic languages (compare German Flut, Dutch vloed from the same root as is seen in flow, float; also compare with Latin fluctus, flumen). Deluge myths are mythical stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution, and are featured in the mythology of many cultures. Contents [hide] • 1 Principal types and causes o 1.1 Areal o 1.2 Riverine o 1.3 Estuarine o 1.4 Coastal o 1.5 Catastrophic o 1.6 Human-induced • 2 Effects o 2.1 Primary effects o 2.2 Secondary effects o 2.3 Tertiary and long-term effects • 3 Control o 3.1 Europe o 3.2 North America o 3.3 Asia o 3.4 Africa o 3.5 Clean-up safety • 4 Benefits • 5 Computer modelling • 6 Deadliest floods • 7 See also • 8 References • 9 Bibliography • 10 External links [edit]Principal types and causes [edit]Areal Floods often happen over flat or low-lying areas when the ground is saturated and water either cannot run off, or cannot run off quickly enough to stop accumulating. This may be later followed by a river flood as water moves away from the areal floodplain into local rivers and streams. Floods can occur if water accumulates across an impermeable surface (e.g. from rainfall) and cannot rapidly dissipate (i.e. gentle orientation or low evaporation). A series of storms moving over the same area can cause areal flash flooding. A muddy flood is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bed load. Muddy runoff is more likely detected when it reaches inhabited areas. Muddy floods are therefore a hill slope process, and confusion with mudflows produced by mass movements should be avoided. [edit]Riverine Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Causes include heavy rains from monsoons, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack. Unexpected drainage obstructions such as landslides, ice, or debris can cause slow flooding upstream of the obstruction. Fast kinds: include river flash floods resulting from convective precipitation (intensethunderstorms) or sudden release from an upstream impoundment created behind a dam,landslide, or glacier. Dam-building beavers can flood low-lying urban and rural areas, often causing significant damage. [edit]Estuarine Commonly caused by a combination of sea tidal surges caused by storm-force winds and high river stages due to heavy rain. [edit]Coastal Caused by severe sea storms, or as a result of another hazard (e.g. tsunami or hurricane). A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. [edit]Catastrophic Caused by a significant and unexpected event e.g. dam breakage, or as a result of another hazard (e.g. earthquake or volcanic eruption). See outburst flood. [edit]Human-induced Accidental damage by workmen to tunnels or pipes. [edit]Effects [edit]Primary effects Physical damage – damage to structures, including bridges, buildings, sewerage systems, roadways, and canals. [edit]Secondary effects Water supplies – Contamination of water. Clean drinking water will become scarce. Diseases – Unhygienic conditions. Spread of water-borne diseases. Crops and food supplies – Shortage of food crops can be caused due to loss of entire harvest.[4] However, lowlands near rivers depend upon river silt deposited by floods in order to add nutrients to the local soil. Trees – Non-tolerant species can die from suffocation.[5] Transport – Transport links destroyed, so hard to get emergency aid to those who need it. [edit]Tertiary and long-term effects Economic – economic hardship due to temporary decline in tourism, rebuilding costs, food shortage leading to price increase, etc. Psychological – flooding can be highly traumatic for individuals, in particular where deaths, serious injuries and loss of property occurs.
A flood is an overflow of water that submerges land.[1] The European Union (EU) Floods Directive defines a flood as a covering by water of land not normally covered by water.[2] In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries,[3] or may be due to accumulation of rainwater on saturated ground in an areal flood. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area. Floods can also occur in rivers, when flow exceeds the capacity of the river channel, particularly at bends or meanders. Floods often cause damage to homes and businesses if they are placed in natural flood plains of rivers. While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and commerce by being near water. That humans continue to inhabit areas threatened by flood damage is evidence that the perceived value of living near the water exceeds the cost of repeated periodic flooding. The word "flood" comes from the Old English flod, a word common to Germanic languages (compare German Flut, Dutch vloed from the same root as is seen in flow, float; also compare with Latin fluctus, flumen). Deluge myths are mythical stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution, and are featured in the mythology of many cultures. Contents [hide] • 1 Principal types and causes o 1.1 Areal o 1.2 Riverine o 1.3 Estuarine o 1.4 Coastal o 1.5 Catastrophic o 1.6 Human-induced • 2 Effects o 2.1 Primary effects o 2.2 Secondary effects o 2.3 Tertiary and long-term effects • 3 Control o 3.1 Europe o 3.2 North America o 3.3 Asia o 3.4 Africa o 3.5 Clean-up safety • 4 Benefits • 5 Computer modelling • 6 Deadliest floods • 7 See also • 8 References • 9 Bibliography • 10 External links [edit]Principal types and causes [edit]Areal Floods often happen over flat or low-lying areas when the ground is saturated and water either cannot run off, or cannot run off quickly enough to stop accumulating. This may be later followed by a river flood as water moves away from the areal floodplain into local rivers and streams. Floods can occur if water accumulates across an impermeable surface (e.g. from rainfall) and cannot rapidly dissipate (i.e. gentle orientation or low evaporation). A series of storms moving over the same area can cause areal flash flooding. A muddy flood is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bed load. Muddy runoff is more likely detected when it reaches inhabited areas. Muddy floods are therefore a hill slope process, and confusion with mudflows produced by mass movements should be avoided. [edit]Riverine Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Causes include heavy rains from monsoons, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack. Unexpected drainage obstructions such as landslides, ice, or debris can cause slow flooding upstream of the obstruction. Fast kinds: include river flash floods resulting from convective precipitation (intensethunderstorms) or sudden release from an upstream impoundment created behind a dam,landslide, or glacier. Dam-building beavers can flood low-lying urban and rural areas, often causing significant damage. [edit]Estuarine Commonly caused by a combination of sea tidal surges caused by storm-force winds and high river stages due to heavy rain. [edit]Coastal Caused by severe sea storms, or as a result of another hazard (e.g. tsunami or hurricane). A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. [edit]Catastrophic Caused by a significant and unexpected event e.g. dam breakage, or as a result of another hazard (e.g. earthquake or volcanic eruption). See outburst flood. [edit]Human-induced Accidental damage by workmen to tunnels or pipes. [edit]Effects [edit]Primary effects Physical damage – damage to structures, including bridges, buildings, sewerage systems, roadways, and canals. [edit]Secondary effects Water supplies – Contamination of water. Clean drinking water will become scarce. Diseases – Unhygienic conditions. Spread of water-borne diseases. Crops and food supplies – Shortage of food crops can be caused due to loss of entire harvest.[4] However, lowlands near rivers depend upon river silt deposited by floods in order to add nutrients to the local soil. Trees – Non-tolerant species can die from suffocation.[5] Transport – Transport links destroyed, so hard to get emergency aid to those who need it. [edit]Tertiary and long-term effects Economic – economic hardship due to temporary decline in tourism, rebuilding costs, food shortage leading to price increase, etc. Psychological – flooding can be highly traumatic for individuals, in particular where deaths, serious injuries and loss of property occurs.
No comments:
Post a Comment