The Barotse Floodplain, also known as the Bulozi Plain , Lyondo or the Zambezi Floodplain, is one of Africa's great wetlands , on the Zambezi River in the Western Province of Zambia . It is a designated Ramsar site , regarded as being of high conservation value.
49-539: The name recognises the floodplain as spawning the culture and way of life of the Lozi people , "Rotse" being a variant of Lozi , and "Ba" meaning "people". They became a powerful kingdom in Central / Southern Africa under their king or litunga Lewanika , whose realm extended up to 300 km from the plain and was called Barotseland . The region is a flat plateau at an elevation of about 1000 m, tilting very slightly to
98-471: A 46-kilometre causeway across the centre of the floodplain to take a paved highway from Mongu to Kalabo , via the ferry across the main river channel at Sandaula, which would then be replaced by a 500-metre bridge. It is treated as an extension of the Lusaka-Mongu Road from Lusaka . Originally intended to be completed in 2006, it has been delayed by the difficulty of building on the floodplain. There
147-620: A channel down into it, and so acts a bit like a dam. Behind it, the floodplain has formed. Below the falls, the river flows nearly twice as fast as it does on the plain and flows more swiftly in a narrower valley less prone to flooding. The floodplain stretches from the Zambezi's confluence with the Kabompo and Lungwebungu Rivers in the north, to a point about 230 km south, above the Ngonye falls and south of Senanga . Along most of its length its width
196-543: 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
245-445: 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
294-447: A large permanent lake and swamps, and a much smaller area which dries out annually. The satellite photo was taken in April 2004 at the peak of the flood, Note that the northern part of the plain, near Lukulu, is less flooded, the land there varies a bit more in height and the water tends to keep to the many river channels. The peak of the flood occurs on the floodplain about 3 months after
343-546: 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
392-406: 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
441-401: Is an area of land adjacent to 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
490-498: 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
539-456: 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 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
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#1732858593822588-565: 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
637-402: 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 is topped by a channel belt formed by successive generations of channel migration and meander cutoff. At much longer intervals,
686-445: Is no rock in the region, and the causeway has been built from sand and gravel scooped out from shallow depressions next to it. Higher than usual floods washed away large sections. The contractor was a Kuwait -based company which acknowledged that conditions were difficult. The Times of Zambia reported that the company underestimated the floodplain environment, and abandoned the contract. Subsequent modifications have been made to raise
735-604: Is over 30 km, reaching 50 km at the widest, just north of Mongu , principal town of the plain, situated at its edge. The main body of the plain covers about 5500 km, but the maximum flooded area is 10 750 km when the floodplains of several tributaries are taken into account, such as the Luena Flats . The Barotse Floodplain is the second largest wetland in Zambia after the Lake Bangweulu system, which differs in having
784-558: The Kafue Flats , is potentially damaging to the environment. Development on the plain has been restricted until now to— Tight control over access to the floodplain by the Litunga and the homogeneity of the indigenous people have slowed commercial development by outsiders. A new project, the Mongu-Kalabo road , will have more far-reaching consequences. Around 2002 construction started of
833-547: 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
882-703: 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
931-545: 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
980-400: 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
1029-511: 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
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#17328585938221078-551: The cattle grazed by the Lozi, but they have provided a large game reserve on the dry grassland to the west, the Liuwa Plain National Park , once the Litunga's hunting grounds, established as a game reserve by Lewanika in the 19th century. In addition the entire western of the Zambezi within the country is a Game Management Area. About 250,000 people live on the plain with a similar number of cattle, migrating to grasslands at
1127-461: 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 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
1176-509: The east and south, and patches of evergreen forest ( Cryptosepalum dry forests ) in the north and east. The flood provides aquatic habitats for fish such as tigerfish and bream , crocodiles , hippopotamus , waterbirds, fish-eating birds, and lechwe , the wading antelope . After the flood, the plain is a habitat for grazing animals such as wildebeest , zebra , tsessebe and small antelope such oribi and steenbok , and their predators. These herbivores have been displaced in most areas by
1225-404: The edge of the floodplain when the flood arrives. The floodplain is one of the most productive areas for raising cattle in the country. The Lozi also catch fish, eating about five times as much as the national average. At the height of the flood they use fish traps and spears for fishing, and they use gill nets in the lagoons left behind by the falling flood. Fish spawn just before the flood,
1274-452: The first floodwaters are naturally hypoxic (low in oxygen) which kills most fish, while eggs survive. The Lozi cultivate crops on the floodplain such as maize , rice , sweet potato , and sugar cane . November to January are lean months. Stored produce from the previous growing season is almost used up and in any case would need to be transported during the migration, while the new season's crops and grasses are not yet productive, and at
1323-598: The flood as well as humus from vegetation killed by the initial flood, and from decaying aquatic plants left to dry out in the mud. It provides a good soil, but in the late dry season it bakes hard in the heat of the sun. As the floods recede, water is left behind in lagoons, swamps, and oxbow lakes . The floodplain is in the Zambezian flooded grasslands ecoregion , and is bordered by slightly higher sandy ground on which grow dry grasslands ( Western Zambezian grasslands ) with woodland savanna ( Zambezian Baikiaea woodlands ) to
1372-629: The flood is celebrated in the Kuomboka ceremony held at Mongu, capital of Barotseland and its successor, the Western Province. In the occasional very wet year such as 2005, lives and property are lost in floods on the Barotse Plain. More often, however, it is a very good example of the principle that natural annual flooding by rivers is valuable and productive for wildlife and human populations, while damming rivers to control floods, as has happened with
1421-468: The flood waters. This can encourage farming ; some important agricultural regions, such as 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
1470-448: 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
1519-462: 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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1568-579: 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 ,
1617-530: 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. Liuwa Plain National Park Too Many Requests If you report this error to
1666-465: 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
1715-448: The inside of river meanders and by overbank flow. Wherever the river meanders, 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
1764-417: The inside so that the channel shifts in 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
1813-457: 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 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
1862-617: 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
1911-754: 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
1960-607: The peak of the rainy season in January–February. The flood usually peaks in April, and recedes in May to July, when grasses quickly grow on the exposed plain. At the river's lowest water in November the floodplain still contains about 537 km of lagoons , swamps and channels. The flood leaves behind a fertile grey to black soil overlaying the Kalahari sands, enriched by silt deposited by
2009-580: 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
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2058-511: 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
2107-418: 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 a channel. Sediments from the crevasse spread out as delta -shaped deposits with numerous distributary channels. Crevasse formation
2156-654: The road height and to increase the number and size of culverts , and this in turn led to funding problems. The road has been completed in 2016. A Chinese contractor, the Aviation Industry Corporation of China (AVIC International), finished the 286.9 million US dollars project. The road stretches 34 Kilometres in the Baroste plains with 26 bridges across it. 15°2′S 22°53′E / 15.033°S 22.883°E / -15.033; 22.883 Floodplain A floodplain or flood plain or bottomlands
2205-407: The same time fishing stops for the spawning season. Hunting and trapping animals, which might have filled the gap, is no longer available to most people, and trapping waterbirds is one of the few alternatives to buying flour. The floodplain determines and dominates the way of life, economy, society and culture of the Lozi, who are skilled boat-builders, paddlers and swimmers. The annual migration with
2254-472: The south. The Zambezi and its headwaters rise on the higher ground to the north, which enjoys good rainfall (1400 mm annually) in a rainy season from October to May. A flood moves down the river, reaching a flat region formed from Kalahari sands, about five hundred kilometres across. To the south, around the Ngonye Falls , harder rock is found at the surface and has resisted the river's tendency to cut
2303-408: 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
2352-459: 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
2401-672: 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
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