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88-513: Around 1700, country estates for several noblemen were established in the former flood plain of the river Leine . In 1726, the Herrenhäuser Allee (Herrenhausen alley) was planted just through the gardens, connecting Hanover with the royal palace and gardens of Herrenhausen in the boroughs of the city; it is almost exactly one geographical mile (1.8553 km or 1.1528 mi) long, and consists of four rows of lime trees . In 1768

176-449: A dam , landslide, or glacier . In one instance, a flash flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the flow rate increased from about 50 to 1,500 cubic feet per second (1.4 to 42 m /s) in just one minute. Two larger floods occurred at the same site within a week, but no one was at the waterfall on those days. The deadly flood resulted from

264-646: A flash flood . Flash floods usually result from intense rainfall over a relatively small area, or if the area was already saturated from previous precipitation. The amount, location, and timing of water reaching a drainage channel from natural precipitation and controlled or uncontrolled reservoir releases determines the flow at downstream locations. Some precipitation evaporates, some slowly percolates through soil, some may be temporarily sequestered as snow or ice, and some may produce rapid runoff from surfaces including rock, pavement, roofs, and saturated or frozen ground. The fraction of incident precipitation promptly reaching

352-515: A landslide , earthquake or volcanic eruption . Examples include outburst floods and lahars . Tsunamis can cause catastrophic coastal flooding , most commonly resulting from undersea earthquakes. The primary effects of flooding include loss of life and damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals. The economic impacts caused by flooding can be severe. Every year flooding causes countries billions of dollars worth of damage that threatens

440-464: A river . Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high discharge . The soils usually consist of clays, silts , sands, and gravels deposited during floods. Because of regular flooding, floodplains frequently have high soil-fertility since nutrients are deposited with the flood waters. This can encourage farming ; some important agricultural regions, such as

528-484: A tropical cyclone or an extratropical cyclone , falls within this category. A storm surge is "an additional rise of water generated by a storm, over and above the predicted astronomical tides". Due to the effects of climate change (e.g. sea level rise and an increase in extreme weather events) and an increase in the population living in coastal areas, the damage caused by coastal flood events has intensified and more people are being affected. Flooding in estuaries

616-407: A channel. Sediments from the crevasse spread out as delta -shaped deposits with numerous distributary channels. Crevasse formation is most common in sections of rivers where the river bed is accumulating sediments ( aggrading ). Repeated flooding eventually builds up an alluvial ridge, whose natural levees and abandoned meander loops may stand well above most of the floodplain. The alluvial ridge

704-468: A country can be lost in extreme flood circumstances. Some tree species may not survive prolonged flooding of their root systems. Flooding in areas where people live also has significant economic implications for affected neighborhoods. In the United States , industry experts estimate that wet basements can lower property values by 10–25 percent and are cited among the top reasons for not purchasing

792-538: A drainage channel has been observed from nil for light rain on dry, level ground to as high as 170 percent for warm rain on accumulated snow. Most precipitation records are based on a measured depth of water received within a fixed time interval. Frequency of a precipitation threshold of interest may be determined from the number of measurements exceeding that threshold value within the total time period for which observations are available. Individual data points are converted to intensity by dividing each measured depth by

880-627: A few minutes for roof and parking lot drainage structures, while cumulative rainfall over several days would be critical for river basins. Water flowing downhill ultimately encounters downstream conditions slowing movement. The final limitation in coastal flooding lands is often the ocean or some coastal flooding bars which form natural lakes . In flooding low lands, elevation changes such as tidal fluctuations are significant determinants of coastal and estuarine flooding. Less predictable events like tsunamis and storm surges may also cause elevation changes in large bodies of water. Elevation of flowing water

968-605: A few. Gastrointestinal disease and diarrheal diseases are very common due to a lack of clean water during a flood. Most of clean water supplies are contaminated when flooding occurs. Hepatitis A and E are common because of the lack of sanitation in the water and in living quarters depending on where the flood is and how prepared the community is for a flood. When floods hit, people lose nearly all their crops, livestock, and food reserves and face starvation. Floods also frequently damage power transmission and sometimes power generation , which then has knock-on effects caused by

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1056-554: A flood-prone property to qualify for government-subsidized insurance, a local community must adopt an ordinance that protects the floodway and requires that new residential structures built in Special Flood Hazard Areas be elevated to at least the level of the 100-year flood. Commercial structures can be elevated or floodproofed to or above this level. In some areas without detailed study information, structures may be required to be elevated to at least two feet above

1144-445: A floodplain. The quantity of sediments in a floodplain greatly exceeds the river load of sediments. Thus, floodplains are an important storage site for sediments during their transport from where they are generated to their ultimate depositional environment. When the rate at which the river is cutting downwards becomes great enough that overbank flows become infrequent, the river is said to have abandoned its floodplain. Portions of

1232-728: A home. According to the U.S. Federal Emergency Management Agency (FEMA), almost 40 percent of small businesses never reopen their doors following a flooding disaster. In the United States, insurance is available against flood damage to both homes and businesses. Economic hardship due to a temporary decline in tourism, rebuilding costs, or food shortages leading to price increases is a common after-effect of severe flooding. The impact on those affected may cause psychological damage to those affected, in particular where deaths, serious injuries and loss of property occur. Fatalities connected directly to floods are usually caused by drowning ;

1320-486: A more distant point controls at higher water levels. Effective flood channel geometry may be changed by growth of vegetation, accumulation of ice or debris, or construction of bridges, buildings, or levees within the flood channel. Periodic floods occur on many rivers, forming a surrounding region known as the flood plain . Even when rainfall is relatively light, the shorelines of lakes and bays can be flooded by severe winds—such as during hurricanes —that blow water into

1408-526: A three-day flood of the Meuse and Rhine Rivers in 1993 found average sedimentation rates in the floodplain of between 0.57 and 1.0 kg/m . Higher rates were found on the levees (4 kg/m or more) and on low-lying areas (1.6 kg/m ). Sedimentation from the overbank flow is concentrated on natural levees, crevasse splays , and in wetlands and shallow lakes of flood basins. Natural levees are ridges along river banks that form from rapid deposition from

1496-413: A thunderstorm over part of the drainage basin, where steep, bare rock slopes are common and the thin soil was already saturated. Flash floods are the most common flood type in normally-dry channels in arid zones, known as arroyos in the southwest United States and many other names elsewhere. In that setting, the first flood water to arrive is depleted as it wets the sandy stream bed. The leading edge of

1584-520: A type of hybrid river/areal flooding can occur, known locally as "overland flooding". This is different from "overland flow" defined as "surface runoff". The Red River Valley is a former glacial lakebed, created by Lake Agassiz , and over a length of 550 mi (890 km), the river course drops only 236 ft (72 m), for an average slope of about 5 inches per mile (or 8.2 cm per kilometer). In this very large area, spring snowmelt happens at different rates in different places, and if winter snowfall

1672-546: Is a problem in freshwater systems. Much of the phosphorus in freshwater systems comes from municipal wastewater treatment plants and agricultural runoff. Stream connectivity controls whether phosphorus cycling is mediated by floodplain sediments or by external processes. Under conditions of stream connectivity, phosphorus is better able to be cycled, and sediments and nutrients are more readily retained. Water in freshwater streams ends up in either short-term storage in plants or algae or long-term in sediments. Wet/dry cycling within

1760-406: Is advantageous for the rapid colonization of large areas of the floodplain. This allows them to take advantage of shifting floodplain geometry. For example, floodplain trees are fast-growing and tolerant of root disturbance. Opportunists (such as birds) are attracted to the rich food supply provided by the flood pulse. Floodplain ecosystems have distinct biozones. In Europe, as one moves away from

1848-405: Is also the intentional flooding of land that would otherwise remain dry. This may take place for agricultural, military, or river-management purposes. For example, agricultural flooding may occur in preparing paddy fields for the growing of semi-aquatic rice in many countries. Flooding may occur as an overflow of water from water bodies, such as a river , lake , sea or ocean. In these cases,

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1936-659: Is an overflow of water ( or rarely other fluids ) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide . Floods are of significant concern in agriculture , civil engineering and public health . Human changes to the environment often increase the intensity and frequency of flooding. Examples for human changes are land use changes such as deforestation and removal of wetlands , changes in waterway course or flood controls such as with levees . Global environmental issues also influence causes of floods, namely climate change which causes an intensification of

2024-498: Is any area subject to inundation by a 100-year flood. A problem is that any alteration of the watershed upstream of the point in question can potentially affect the ability of the watershed to handle water, and thus potentially affects the levels of the periodic floods. A large shopping center and parking lot, for example, may raise the levels of 5-year, 100-year, and other floods, but the maps are rarely adjusted and are frequently rendered obsolete by subsequent development. In order for

2112-419: Is common when heavy flows move uprooted woody vegetation and flood-damaged structures and vehicles, including boats and railway equipment. Recent field measurements during the 2010–11 Queensland floods showed that any criterion solely based upon the flow velocity, water depth or specific momentum cannot account for the hazards caused by velocity and water depth fluctuations. These considerations ignore further

2200-493: Is commonly caused by a combination of storm surges caused by winds and low barometric pressure and large waves meeting high upstream river flows. The intentional flooding of land that would otherwise remain dry may take place for agricultural, military or river-management purposes. This is a form of hydraulic engineering . Agricultural flooding may occur in preparing paddy fields for the growing of semi-aquatic rice in many countries. Flooding for river management may occur in

2288-400: Is controlled by the geometry of the flow channel and, especially, by depth of channel, speed of flow and amount of sediments in it Flow channel restrictions like bridges and canyons tend to control water elevation above the restriction. The actual control point for any given reach of the drainage may change with changing water elevation, so a closer point may control for lower water levels until

2376-565: Is largely a result of flood control, hydroelectric development (such as reservoirs), and conversion of floodplains to agriculture use. Transportation and waste disposal also have detrimental effects. The result is the fragmentation of these ecosystems, resulting in loss of populations and diversity and endangering the remaining fragments of the ecosystem. Flood control creates a sharper boundary between water and land than in undisturbed floodplains, reducing physical diversity. Floodplain forests protect waterways from erosion and pollution and reduce

2464-461: Is more significant to flooding within small drainage basins. The most important upslope factor in determining flood magnitude is the land area of the watershed upstream of the area of interest. Rainfall intensity is the second most important factor for watersheds of less than approximately 30 square miles or 80 square kilometres. The main channel slope is the second most important factor for larger watersheds. Channel slope and rainfall intensity become

2552-708: Is topped by a channel belt formed by successive generations of channel migration and meander cutoff. At much longer intervals, the river may abandon the channel belt and build a new one at another position on the floodplain. This process is called avulsion and occurs at intervals of 10–1000 years. Historical avulsions leading to catastrophic flooding include the 1855 Yellow River flood and the 2008 Kosi River flood . Floodplains can form around rivers of any kind or size. Even relatively straight stretches of river are capable of producing floodplains. Mid-channel bars in braided rivers migrate downstream through processes resembling those in point bars of meandering rivers and can build up

2640-563: The Kosi River of India. Overbank flow takes place when the river is flooded with more water than can be accommodated by the river channel. Flow over the banks of the river deposits a thin veneer of sediments that is coarsest and thickest close to the channel. This is described as vertical accretion , since the deposits build upwards. In undisturbed river systems, overbank flow is frequent, typically occurring every one to two years, regardless of climate or topography. Sedimentation rates for

2728-463: The Nile and Mississippi river basins , heavily exploit floodplains. Agricultural and urban regions have developed near or on floodplains to take advantage of the rich soil and freshwater. However, the risk of inundation has led to increasing efforts to control flooding . Most floodplains are formed by deposition on the inside of river meanders and by overbank flow. Wherever the river meanders,

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2816-562: The Second World War ). Floods are caused by many factors or a combination of any of these generally prolonged heavy rainfall (locally concentrated or throughout a catchment area), highly accelerated snowmelt , severe winds over water, unusual high tides, tsunamis , or failure of dams, levees , retention ponds , or other structures that retained the water. Flooding can be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce

2904-557: The Yellow River in China – see list of deadliest floods . The worst of these, and the worst natural disaster (excluding famine and epidemics), was the 1931 China floods , estimated to have killed millions. This had been preceded by the 1887 Yellow River flood , which killed around one million people and is the second-worst natural disaster in history. The extent of floodplain inundation depends partly on flood magnitude, defined by

2992-684: The return period . In the United States, the Federal Emergency Management Agency (FEMA) manages the National Flood Insurance Program (NFIP). The NFIP offers insurance to properties located within a flood-prone area, as defined by the Flood Insurance Rate Map (FIRM), which depicts various flood risks for a community. The FIRM typically focuses on the delineation of the 100-year flood inundation area, also known within

3080-562: The water table is shallow, such as a floodplain , or from intense rain from one or a series of storms . Infiltration also is slow to negligible through frozen ground, rock, concrete , paving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience areal flooding during periods when precipitation exceeds evaporation. Floods occur in all types of river and stream channels, from

3168-591: The British troop vehicles damaged many of the lime trees of the old Herrenhäuser Allee. Their step-by-step restoration took until the 1970s. Since 1949, ownership of the Georgenpalais was transferred to the Wilhelm Busch Society, a literary society named after the famous German caricaturist, painter and poet Wilhelm Busch . They later rebuilt the damaged eastern wing of the building. Today

3256-740: The German lieutenant-general and art collector Johann Ludwig, Reichsgraf von Wallmoden-Gimborn acquired some of these gardens and merged them into the Wallmodengarten. Between 1780 and 1782 he built his own palace there, the Wallmodenschloss (also called Wallmodenpalais) to house his antiquities collection. In order to enlarge the royal gardens of Hanover, the Wallmoden palace and the Wallmoden garden 1817 were sold to George III , who had been King of Hanover since 1814. From 1818 on,

3344-560: The NFIP as the Special Flood Hazard Area. Where a detailed study of a waterway has been done, the 100-year floodplain will also include the floodway, the critical portion of the floodplain which includes the stream channel and any adjacent areas that must be kept free of encroachments that might block flood flows or restrict storage of flood waters. Another commonly encountered term is the Special Flood Hazard Area, which

3432-400: The abandoned floodplain may be preserved as fluvial terraces . Floodplains support diverse and productive ecosystems . They are characterized by considerable variability in space and time, which in turn produces some of the most species-rich of ecosystems. From the ecological perspective, the most distinctive aspect of floodplains is the flood pulse associated with annual floods, and so

3520-511: The advantages provided by the richness of the alluvial soil of the floodplain are severely offset by frequent floods brought on by cyclones and annual monsoon rains. These extreme weather events cause severe economic disruption and loss of human life in the densely-populated region. Floodplain soil composition is unique and varies widely based on microtopography. Floodplain forests have high topographic heterogeneity which creates variation in localized hydrologic conditions. Soil moisture within

3608-717: The adverse ecological impact of the inundation. That impact may also be adverse in a hydrogeological sense if the inundation lasts a long time. Examples for uncontrolled inundations are the second Siege of Leiden during the first part of the Eighty Years' War , the flooding of the Yser plain during the First World War , and the Inundation of Walcheren , and the Inundation of the Wieringermeer during

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3696-532: The alley by paying 3,000 Taler . To honour Helmcke's deed, a memorial stone was placed near the alley. In 1921 the City of Hanover bought both the Georgengarten and the Georgenpalais. During World War II the Georgenpalais was damaged severely by bombs during a Royal Air Force air raid. The Georgengarten was used to grow vegetables. In post war military occupation years, a lot of seeping engine oil and fuel of

3784-423: The amount of water damage and mold that grows after an incident. Research suggests that there will be an increase of 30–50% in adverse respiratory health outcomes caused by dampness and mold exposure for those living in coastal and wetland areas. Fungal contamination in homes is associated with increased allergic rhinitis and asthma. Vector borne diseases increase as well due to the increase in still water after

3872-480: The city end of the Herrenhäuser Allee, in 1857, a gate was built after plans made by Laves. The gate separated Königsworther Platz (Königsworther square) from the alley and the Georgengarten. In the 1960s, the gate was demolished, but in 2007, a replica with some remaining original parts was placed there. At the end of 19th century Napoleonic troops were going to cut down the whole Herrenhäuser Allee, but baker and grain dealer Johann Gerhard Helmcke (1780−1844) saved

3960-434: The deadliest floods worldwide, showing events with death tolls at or above 100,000 individuals. Floods (in particular more frequent or smaller floods) can also bring many benefits, such as recharging ground water , making soil more fertile and increasing nutrients in some soils. Flood waters provide much needed water resources in arid and semi-arid regions where precipitation can be very unevenly distributed throughout

4048-515: The direction of the meander without changing significantly in width. The point bar is built up to a level very close to that of the river banks. Significant net erosion of sediments occurs only when the meander cuts into higher ground. The overall effect is that, as the river meanders, it creates a level flood plain composed mostly of point bar deposits. The rate at which the channel shifts varies greatly, with reported rates ranging from too slow to measure to as much as 2,400 feet (730 m) per year for

4136-576: The field that is intended to impede the movement of the enemy. This may be done both for offensive and defensive purposes. Furthermore, in so far as the methods used are a form of hydraulic engineering, it may be useful to differentiate between controlled inundations and uncontrolled ones. Examples for controlled inundations include those in the Netherlands under the Dutch Republic and its successor states in that area and exemplified in

4224-470: The flood process; before, during and after. During floods accidents occur with falling debris or any of the many fast moving objects in the water. After the flood rescue attempts are where large numbers injuries can occur. Communicable diseases are increased due to many pathogens and bacteria that are being transported by the water .There are many waterborne diseases such as cholera , hepatitis A , hepatitis E and diarrheal diseases , to mention

4312-492: The flood thus advances more slowly than later and higher flows. As a result, the rising limb of the hydrograph becomes ever quicker as the flood moves downstream, until the flow rate is so great that the depletion by wetting soil becomes insignificant. Coastal areas may be flooded by storm surges combining with high tides and large wave events at sea, resulting in waves over-topping flood defenses or in severe cases by tsunami or tropical cyclones. A storm surge , from either

4400-448: The floodplain ecosystem is defined as the part of the river valley that is regularly flooded and dried. Floods bring in detrital material rich in nutrients and release nutrients from dry soil as it is flooded. The decomposition of terrestrial plants submerged by the floodwaters adds to the nutrient supply. The flooded littoral zone of the river (the zone closest to the river bank) provides an ideal environment for many aquatic species, so

4488-462: The floodplain has a big impact on phosphorus availability because it alters water level, redox state, pH, and physical properties of minerals. Dry soils that were previously inundated have reduced availability of phosphorus and increased affinity for obtaining phosphorus. Human floodplain alterations also impact the phosphorus cycle. Particulate phosphorus and soluble reactive phosphorus (SRP) can contribute to algal blooms and toxicity in waterways when

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4576-599: The floodplain. Other smaller-scale mitigation efforts include acquiring and demolishing flood-prone buildings or flood-proofing them. In some floodplains, such as the Inner Niger Delta of Mali , annual flooding events are a natural part of the local ecology and rural economy , allowing for the raising of crops through recessional agriculture . However, in Bangladesh , which occupies the Ganges Delta ,

4664-403: The floods have settled. The diseases that are vector borne are malaria , dengue , West Nile , and yellow fever . Floods have a huge impact on victims' psychosocial integrity . People suffer from a wide variety of losses and stress . One of the most treated illness in long-term health problems are depression caused by the flood and all the tragedy that flows with one. Below is a list of

4752-428: The flow rate exceeds the capacity of the river channel , particularly at bends or meanders in the waterway . Floods often cause damage to homes and businesses if these buildings are in the natural flood plains of rivers. People could avoid riverine flood damage by moving away from rivers. However, people in many countries have traditionally lived and worked by rivers because the land is usually flat and fertile . Also,

4840-404: The flowing water erodes the river bank on the outside of the meander. At the same time, sediments are simultaneously deposited in a bar on the inside of the meander. This is described as lateral accretion since the deposition builds the point bar laterally into the river channel. Erosion on the outside of the meander usually closely balances deposition on the inside so that the channel shifts in

4928-605: The form of diverting flood waters in a river at flood stage upstream from areas that are considered more valuable than the areas that are sacrificed in this way. This may be done ad hoc , or permanently, as in the so-called overlaten (literally "let-overs"), an intentionally lowered segment in Dutch riparian levees, like the Beerse Overlaat in the left levee of the Meuse between the villages of Gassel and Linden, North Brabant . Military inundation creates an obstacle in

5016-478: The house is used as a caricature museum and is named Wilhelm-Busch-Museum - Deutsches Museum für Karikatur und kritische Grafik . The Georgengarten now is a part of the famous Herrenhausen Gardens . The Leibniz Temple in the park is named in honour of the German polymath Gottfried Leibniz . Originally it was erected between 1787 and 1790 at the Hanover military parade place (now called Waterlooplatz); later it

5104-398: The human-caused disconnect between floodplains and rivers exacerbates the phosphorus overload. Floodplain soils tend to be high in eco-pollutants, especially persistent organic pollutant (POP) deposition. Proper understanding of the distribution of soil contaminants is difficult because of high variation in microtopography and soil texture within floodplains. Flood A flood

5192-465: The impact of floodwaters. The disturbance by humans of temperate floodplain ecosystems frustrates attempts to understand their natural behavior. Tropical rivers are less impacted by humans and provide models for temperate floodplain ecosystems, which are thought to share many of their ecological attributes. Excluding famines and epidemics , some of the worst natural disasters in history (measured by fatalities) have been river floods, particularly in

5280-403: The land in quantities that cannot be carried within stream channels or retained in natural ponds, lakes, and human-made reservoirs . About 30 percent of all precipitation becomes runoff and that amount might be increased by water from melting snow. River flooding is often caused by heavy rain, sometimes increased by melting snow. A flood that rises rapidly, with little or no warning, is called

5368-614: The livelihood of individuals. As a result, there is also significant socio-economic threats to vulnerable populations around the world from flooding. For example, in Bangladesh in 2007, a flood was responsible for the destruction of more than one million houses. And yearly in the United States, floods cause over $ 7 billion in damage. Flood waters typically inundate farm land, making the land unworkable and preventing crops from being planted or harvested, which can lead to shortages of food both for humans and farm animals. Entire harvests for

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5456-417: The location of the flood. Damage to roads and transport infrastructure may make it difficult to mobilize aid to those affected or to provide emergency health treatment. Flooding can cause chronically wet houses, leading to the growth of indoor mold and resulting in adverse health effects, particularly respiratory symptoms. Respiratory diseases are a common after the disaster has occurred. This depends on

5544-436: The loss of power. This includes loss of drinking water treatment and water supply, which may result in loss of drinking water or severe water contamination. It may also cause the loss of sewage disposal facilities. Lack of clean water combined with human sewage in the flood waters raises the risk of waterborne diseases , which can include typhoid , giardia , cryptosporidium , cholera and many other diseases depending upon

5632-617: The makeup towards ash (49%) with maple increasing to 14% and oak decreasing to 25%. Semiarid floodplains have a much lower species diversity. Species are adapted to alternating drought and flood. Extreme drying can destroy the ability of the floodplain ecosystem to shift to a healthy wet phase when flooded. Floodplain forests constituted 1% of the landscape of Europe in the 1800s. Much of this has been cleared by human activity, though floodplain forests have been impacted less than other kinds of forests. This makes them important refugia for biodiversity. Human destruction of floodplain ecosystems

5720-762: The nitrogen-to-phosphorus ratios are altered farther upstream. In areas where the phosphorus load is primarily particulate phosphorus, like the Mississippi River, the most effective ways of removing phosphorus upstream are sedimentation, soil accretion, and burial. In basins where SRP is the primary form of phosphorus, biological uptake in floodplain forests is the best way of removing nutrients. Phosphorus can transform between SRP and particulate phosphorus depending on ambient conditions or processes like decomposition, biological uptake, redoximorphic release, and sedimentation and accretion. In either phosphorus form, floodplain forests are beneficial as phosphorus sinks, and

5808-442: The overbank flow. Most of the suspended sand is deposited on the levees, leaving the silt and clay sediments to be deposited as floodplain mud further from the river. Levees are typically built up enough to be relatively well-drained compared with nearby wetlands, and levees in non-arid climates are often heavily vegetated. Crevasses are formed by breakout events from the main river channel. The river bank fails, and floodwaters scour

5896-423: The palace was named Georgenpalais and the gardens name changed into Georgengarten. In 1826 the architect and engineer Georg Ludwig Friedrich Laves designed two smaller wings adjacent to the left and right side of the Wallmodenschloss. From 1828 until 1843 the formal garden was redesigned as an English style landscape garden. Former water features, canals and so on, were enlarged into a pond. Between 1835 and 1841

5984-457: The period of time between observations. This intensity will be less than the actual peak intensity if the duration of the rainfall event was less than the fixed time interval for which measurements are reported. Convective precipitation events (thunderstorms) tend to produce shorter duration storm events than orographic precipitation. Duration, intensity, and frequency of rainfall events are important to flood prediction. Short duration precipitation

6072-586: The result of sustained rainfall, rapid snow melt, monsoons , or tropical cyclones . However, large rivers may have rapid flooding events in areas with dry climates, since they may have large basins but small river channels, and rainfall can be very intense in smaller areas of those basins. In extremely flat areas, such as the Red River Valley of the North in Minnesota , North Dakota , and Manitoba ,

6160-480: The risks associated with large debris entrained by the flow motion. Floods can be a huge destructive power. When water flows, it has the ability to demolish all kinds of buildings and objects, such as bridges, structures, houses, trees, and cars. Economical, social and natural environmental damages are common factors that are impacted by flooding events and the impacts that flooding has on these areas can be catastrophic. There have been numerous flood incidents around

6248-511: The river, the successive plant communities are bank vegetation (usually annuals); sedge and reeds; willow shrubs; willow-poplar forest; oak-ash forest; and broadleaf forest. Human disturbance creates wet meadows that replace much of the original ecosystem. The biozones reflect a soil moisture and oxygen gradient that in turn corresponds to a flooding frequency gradient. The primeval floodplain forests of Europe were dominated by oak (60%) elm (20%) and hornbeam (13%), but human disturbance has shifted

6336-454: The rivers provide easy travel and access to commerce and industry. Flooding can damage property and also lead to secondary impacts. These include in the short term an increased spread of waterborne diseases and vector-bourne disesases , for example those diseases transmitted by mosquitos. Flooding can also lead to long-term displacement of residents. Floods are an area of study of hydrology and hydraulic engineering . A large amount of

6424-497: The shore areas. Extreme flood events often result from coincidence such as unusually intense, warm rainfall melting heavy snow pack, producing channel obstructions from floating ice, and releasing small impoundments like beaver dams. Coincident events may cause extensive flooding to be more frequent than anticipated from simplistic statistical prediction models considering only precipitation runoff flowing within unobstructed drainage channels. Debris modification of channel geometry

6512-538: The smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the world's largest rivers. When overland flow occurs on tilled fields, it can result in a muddy flood where sediments are picked up by run off and carried as suspended matter or bed load . Localized flooding may be caused or exacerbated by drainage obstructions such as landslides , ice , debris , or beaver dams. Slow-rising floods most commonly occur in large rivers with large catchment areas . The increase in flow may be

6600-408: The spawning season for fish often coincides with the onset of flooding. Fish must grow quickly during the flood to survive the subsequent drop in water level. As the floodwaters recede, the littoral experiences blooms of microorganisms, while the banks of the river dry out and terrestrial plants germinate to stabilize the bank. The biota of floodplains has high annual growth and mortality rates, which

6688-527: The supply of vegetation that can absorb rainfall. During times of rain, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation, some evaporates, and the rest travels over the land as surface runoff . Floods occur when ponds, lakes, riverbeds, soil, and vegetation cannot absorb all the water. This has been exacerbated by human activities such as draining wetlands that naturally store large amounts of water and building paved surfaces that do not absorb any water. Water then runs off

6776-459: The surrounding grade. Many State and local governments have, in addition, adopted floodplain construction regulations which are more restrictive than those mandated by the NFIP. The US government also sponsors flood hazard mitigation efforts to reduce flood impacts. California 's Hazard Mitigation Program is one funding source for mitigation projects. A number of whole towns such as English, Indiana , have been completely relocated to remove them from

6864-727: The then head gardener, Christian Schaumburg, was responsible for some redesign. During these years, three bridges designed by Laves were built: 1837 the Fahrbrücke, in 1840 the Augustenbrücke, and in the same year, the Friederikenbrücke. The latter is the only remaining bridge of the three. Today it connects the Georgengarten and the Great Garden (Großer Garten) within the Herrenhausen Gardens. At

6952-440: The third most important factors for small and large watersheds, respectively. Time of Concentration is the time required for runoff from the most distant point of the upstream drainage area to reach the point of the drainage channel controlling flooding of the area of interest. The time of concentration defines the critical duration of peak rainfall for the area of interest. The critical duration of intense rainfall might be only

7040-699: The two Hollandic Water Lines , the Stelling van Amsterdam , the Frisian Water Line , the IJssel Line , the Peel-Raam Line , and the Grebbe line in that country. To count as controlled , a military inundation has to take the interests of the civilian population into account, by allowing them a timely evacuation , by making the inundation reversible , and by making an attempt to minimize

7128-672: The upper 30 cm of the soil profile also varies widely based on microtopography which affects oxygen availability. Floodplain soil stays aerated for long stretches of time in between flooding events, but during flooding, saturated soil can become oxygen-depleted if it stands stagnant for long enough. More soil oxygen is available at higher elevations farther from the river. Floodplain forests generally experience alternating periods of aerobic and anaerobic soil microbe activity which affects fine root development and desiccation. Floodplains have high buffering capacity for phosphorus to prevent nutrient loss to river outputs. Phosphorus nutrient loading

7216-441: The water cycle and sea level rise . For example, climate change makes extreme weather events more frequent and stronger. This leads to more intense floods and increased flood risk. Natural types of floods include river flooding, groundwater flooding coastal flooding and urban flooding sometimes known as flash flooding. Tidal flooding may include elements of both river and coastal flooding processes in estuary areas. There

7304-487: The water overtops or breaks levees , resulting in some of that water escaping its usual boundaries. Flooding may also occur due to an accumulation of rainwater on saturated ground. This is called an areal flood . The size of a lake or other body of water naturally varies with seasonal changes in precipitation and snow melt. Those changes in size are however not considered a flood unless they flood property or drown domestic animals . Floods can also occur in rivers when

7392-515: The waters in a flood are very deep and have strong currents . Deaths do not just occur from drowning, deaths are connected with dehydration , heat stroke , heart attack and any other illness that needs medical supplies that cannot be delivered. Injuries can lead to an excessive amount of morbidity when a flood occurs. Injuries are not isolated to just those who were directly in the flood, rescue teams and even people delivering supplies can sustain an injury. Injuries can occur anytime during

7480-450: The world which have caused devastating damage to infrastructure, the natural environment and human life. Floods can have devastating impacts to human societies. Flooding events worldwide are increasing in frequency and severity, leading to increasing costs to societies. Catastrophic riverine flooding can result from major infrastructure failures, often the collapse of a dam . It can also be caused by drainage channel modification from

7568-557: The world's population lives in close proximity to major coastlines , while many major cities and agricultural areas are located near floodplains . There is significant risk for increased coastal and fluvial flooding due to changing climatic conditions. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either infiltrate or run off . The excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which effectively stops infiltration, where

7656-765: Was heavy, a fast snowmelt can push water out of the banks of a tributary river so that it moves overland, to a point further downstream in the river or completely to another streambed. Overland flooding can be devastating because it is unpredictable, it can occur very suddenly with surprising speed, and in such flat land it can run for miles. It is these qualities that set it apart from simple "overland flow". Rapid flooding events, including flash floods , more often occur on smaller rivers, rivers with steep valleys, rivers that flow for much of their length over impermeable terrain, or normally-dry channels. The cause may be localized convective precipitation (intense thunderstorms ) or sudden release from an upstream impoundment created behind

7744-405: Was transferred to the Georgengarten. Today it is a popular venue during warm summer evenings, especially frequented by young people and students of the nearby Leibniz University Hannover . 52°23′09″N 9°42′29″E  /  52.38582°N 9.70814°E  / 52.38582; 9.70814 Flood plain A floodplain or flood plain or bottomlands is an area of land adjacent to

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