WHAT IS FLOOD?
A simple definition of flooding is water where it is not wanted. Another, more comprehensive definition of a flood is: http://www.floodsite.net/juniorfloodsite/html/en/student/thingstoknow/hydrology/floodtypes.html A flood is a hazard that can occur in many countries of the world. You have probably seen many floods on the news happening somewhere in the world and maybe close to where you live. Floods bring misery to those that live in the area. They can cause loss of life and often cause a great disruption of daily life: water can come into people’s houses, drinking water and electricity supplies may break down, roads can be blocked, people cannot go to work or to school. Floods all over the world cause enormous damages every year like economic damages, damage to the natural environment and damage to national heritage sites. A flood is a situation in which water temporarily covers land where it normally doesn’t. This water comes from the sea, lakes, rivers, canals or sewers. It can also be rainwater.
what is a 100-year flood and how is it determined?
In the 1960�s, the United States government decided to use the 1-percent annual exceedance probability (AEP) flood as the basis for the National Flood Insurance Program. The 1-percent AEP flood was thought to be a fair balance between protecting the public and overly stringent regulation. Because the 1-percent AEP flood has a 1 in 100 chance of being equaled or exceeded in any 1 year, and it has an average recurrence interval of 100 years, it often is referred to as the �100-year flood�. Scientists and engineers frequently use statistical probability (chance) to put a context to floods and their occurrence. If the probability of a particular flood magnitude being equaled or exceeded is known, then risk can be assessed. To determine these probabilities all the annual peak streamflow values measured at a streamgage are examined. A streamgage is a location on a river where the height of the water and the quantity of flow (streamflow) are recorded. The U.S. Geological Survey (USGS) operates more than 7,500 streamgages nationwide (see map) that allow for assessment of the probability of floods. Examining all the annual peak streamflow values that occurred at a streamgage with time allows us to estimate the AEP for various flood magnitudes. For example, we can say there is a 1 in 100 chance that next year�s flood will equal or exceed the 1-percent AEP flood. More recently, people talk about larger floods, such as the �500-year flood,� as tolerance for risk is reduced and increased protection from flooding is desired. The �500-year flood� corresponds to an AEP of 0.2-percent, which means a flood of that size or greater has a 0.2-percent chance (or 1 in 500 chance) of occurring in a given year.
http://www.ga.gov.au/hazards/flood/flood-basics/what/flood-terms.html FLOOD TERM
A floodplain is an area of land adjacent to a creek, river, estuary, lake, dam or artificial channel, which is subject to inundation by floodwater. Most cities and towns in NORTH EASTERN BIHAR, for example DARBHANGA , are located on floodplains. There are ample benefits associated with making use of fertile floodplain lands, but they come with an obvious draw by definition, floodplain land is subject to flooding. FLOOD STUDY
A flood study is the scientific investigation of flooding in a particular area, usually the catchment of a river system. It may involve hydrologic and hydraulic investigations, and a statistical analysis of the frequency with which floods have occurred. The purpose of a flood study is to predict the height of water and the extent to which it will inundate the landscape in a modelled flood event. FLOOD MAP
A flood map is the visual representation of the information contained in a flood study. It is the final outcome of a multitude of measurement, engineering, and data analysis tasks. The elevations of...
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