why is flooding more frequent and severe in areas that have been developed or altered than other areas?
145559
My answer is ot supposed to completly argue on the subject, but it may yet give something to think about!!\n\nBecause when humans come up in an area without changing it, they settle in an armless way (if they notice a flooding risk, they adapt themselves to the area: egyptian with the Nile 3000 years ago for exemple).\nOn the other hand, when they show up and develop altering the area situation, such things as flooding that did not happen before may occur. Which would explain why most of the disaster happen in these cases.\n\nMy opinion is that humans should always try to adapt themselves to the situations instead of trying to adapt the situations to themselves (which tend to be more and more frequent unfortunatly).
688080
yes\nhttp://news.yahoo.com/s/ap/20060516/ap_on_re_us/new_england_flooding;_ylt=AgDzbrtV57Qm6iRL7_1kSiCs0NUE;_ylu=X3oDMTA2Z2szazkxBHNlYwN0bQ--\nthis was my current event
66486
Surface maps only show the conditions near the surface (1000 mb), jet streams and upper level pressure systems have more to do with weather than surface conditions.  The winds and pressures at different elevations can vary greatly from those at the surface.
615594
I'm here.  So are lots of other people.  No, we are not still under flood waters.  Yes, a lot of the city was destroyed and still lies in ruins.  Come see for yourself.
341724
By erosion and quakes and volcanic activity and plate tectonics. that is the natural thing that change it. The unnatural things are construction like the Piramids and the California Aquaduct and power plants and buildings. And the distruction of the rain forests and exploration of the ocians. And so much more. The surface is in constant flux and always changing.
173786
Bangladesh is in a geographic position where numerous revers have run thru it and united in the Bay of Bengal. That places the country particularly vulnerable to flood. But most of these revers have source in Indian land and India has dams over some of the rivers. In the dry season due to dam on the common rivers Bangladesh suffers with dry river beds. During the rainy season India just opens gates of those dams and that makes the situation worse.
1002112
They happen so quickly, there's not a lot you can do in the moment.\n\nBut!  You can pick a place to live that's out of the danger zone appropriately.  You can live on a lake or river, as long as your house is out of the way of known flood zones (for instance, on a man-made lake, make sure your're house is higher in altitude than teh top of the spillway.  That'll make it as safe as you can.
9604
No. They are far too large for any single or even series of rainstorms to have any noticeable affect on the water level. However, if our weather patterns started to change significantly and over many years we had more and more rain, then the water level could rise. It would be a slow process.
964624
There is headward erision (where the upper course erodes at the head), Gulley Erosion( where it forms gorges and gulleys) and there is erosion by debris(bigger rocks or stones along the river bed). These can also cause potholes in the river bed.
363601
Yes, after constructing the dam, they do cause an area to be "flooded" but it is usually a very low-lying wet place anyways. The sad thing is that sometimes they take some historic sites, cemetaries, & even some people's homes. See website below about how Santee Lakes were created in SC. One of SC's Revolutionary War hero's homes *was covered for that purpose.\n\nSediment will keep building up behind a dam. I am not sure if this compromises the structure of the dam; I guess that depends on materials from which the dam was constructed.\n\nThese sediments will start filling in the lake.\n\nFish that go upstream to spawn will have a barrier so it may cut fish populations upstream.\n\nI can't think of anymore.\n\nDownstream is more detrimentally affected than the upstream.\n\nThere is less water being channeled through the stream/river bed. This can be a problem for cities that use the river as a water source or for irrigation.\n\nExample: Colorado River in western US has several dams of which the most notorious are the Glen River & Hoover Dam. I think there are about 6 or 7 along the entire stretch of the river. B/c of this, all the water in the river is completely depleted before it ever reaches the Gulf of California; it actually dries up before it gets there!\n\nKeep in mind, you are in an arid region which requires irrigation. But the whole point of me telling this is that dams are used to reservoir the water & that is where they mostly get their stores/supplies of water.\n\nAnyway, as with anything else, dams serve for good as well as they do for bad. It's just a matter of weighing the whole thing out.\n\n:)
418494
Generally, most river systems were formed on what were originally geological faults.  These areas were naturally lower then the surrounding land mass and as the surface water built up it would naturally drain towards the lowest point.\n\nAs to flooding this is usually where an excess of surface water has developed and the inability of the natural drain to remove or drain off the surface waters.  In this case the waters draining to the river bed simply rises to the point that the "bottle neck" can be over come and the excess water levels are removed from the area.  Once this happens the normal drain capacity and the normal inflow are balanced and the river returns to it's normal river bed.\n\nDave Cooke
715923
1.  Natural disaster...for obvious reasons\n2.  Growth and new industry\n3.  Lack of jobs and mass movement of people to better areas.
759317
The normal cycle is (very simplified): rain, transportation to sea, evaporation.\n\nThe main thing that mankind does to change this is after the rain has fallen and before it reaches the sea.  The main thing being irrigation which diverts water from the river into the surrounding land.  Obviously when water is soaked into the ground it cannot evaporate and so the 'residence time' in this part of the cycle is increased.\nBuilding damns and other structures (ie. cities) will also have similar effects by diverting the natural course of a river.\nWith global warming comes another problem.  Obviously the warmer something is the more energy it has.  This extra energy causes an unstable atmosphere leading to increased rainfall in some areas and less in others.  Rising sea temperature, which is also connected to global warming, will increase the rate of evaporation (which is why there are more hurricanes in the Atlantic).
336494
Rivers & streams are parts of drainage basins (aka watersheds). This means that they drain most of the surface water from an area.\n\nWhen it rains very heavily, it runs off & goes into the rivers & streams b/c they are lower in elevation. This is called surface runoff.\n\nRivers are only capable of handling a certain amount of water at a time. When it reaches flood stage it will overflow it's banks.\n\nAlthough it is possible for a lake to flood, more than likely it will not. It is less likely to get all the surface runoff from the surrounding area.\n\nOceans are not going to flood unless sea level rises. There is no real "normal" flood stage for oceans. Over time they transgress & regress in response to climate change. Water is constantly being evaporated from the oceans as well.\n\nMost of our precipitation comes from water vapor that was evaporated from the oceans. This is simply b/c oceans cover the majority of the planet.\n\nHope this helps.
338188
The causes of the floods in the Severn Valley in 1998 can be split into two sections: human and physical causes. The human causes of the floods were summed up by the then Shadow Countryside Minister Tim Yeo MP, he said ‘the flooding had increased because of the housing developments on Greenfield sites.’ By this he means that by concreting over the land humans have increased the rate of surface runoff and decreased the saturation levels of the ground. When surface runoff is high rainwater reaches the river faster. It would appear that the speed in which the water reached the river was too fast for the river to handle. The river filled up reaching bank-full discharge and then overflowing its banks onto the flood plain. The flood plain of the River Severn is built on, therefore, when the river floods it floods onto residential areas. With the building of these urban areas the amount of vegetation in the area surrounding the river was reduced, this affects the river two ways. It reduces the amount of interception, which in turn increases the speed of runoff into the river. The lack of vegetation also leads to the saturation of the ground. During the months of October and November the rainfall in the Severn Valley was high, as the water soaked into the ground it became saturated. More vegetation in the area would have meant the vegetation using the water would have decreased the amount of water in ground storage. Physical factors of the flood in 1998 are many; however, the most important one was the amount of rainfall. In October 1998 many areas received record amounts of rainfall caused by a ‘hurricane’. This ‘hurricane’ brought very heavy rain and strong winds. The fact the rain was heavy means that the river did not have time to dissipate the water quick enough and the runoff was too fast, making the river rise t such an extent that it flooded. The area of the river upstream was worst effected, the area drown stream was not so badly effected because the river widens down stream. The saturation of the ground meant that any precipitation after the ground began saturated just added to the floodwaters. Other physical factors include the flat and low-lying nature of the landscape surrounding the Severn. This meant that as the water breached the banks it just spread across the land: \n\n\nNumber of Affected Homesteads - 9,80,571 9. Number of Death - 918 10. Cattle heads killed - 26,564 11. Road Damaged (km)- 15,927 12. Embankment Damaged (km)- 4,528 13. Number of Damaged Bridge /Culverts- 6,890 14. Number of Educational Institutions - 1,718 15. Number of Flood Shelter - 2,716 16. Number of People take refuge - 10,49,525 Bangladesh - Floods OCHA Situation Report The Ministry of Disaster Management and Relief as of 15 September 1998 provided the following update on flood damage: Districts Affected: 52 Thanas affected: 366 Persons affected: 30.6 million Total dead: 783 Crops damaged: 1,497,500 (acres) Houses damaged: 894,015 Roads damaged: 15,900 (km) Embankment damaged: 4,451 (km) Shelters: 2,661 Sheltered people: 1 million
245619
FEMA defines it as: "the flood elevation that has a 1- percent chance of being equaled or exceeded each year." This doesn't mean the area can expect a flood every 100 years. The 100-year flood plain is often used by towns and cities when planning developments and roads. Structures or homes built within the 100-year flood plain often need special permits or flood insurance.
91009
It obstructs the natural flow of water, flooding areas previously dry and depriving downstream areas of water.