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47-659: The district comprises the floodplain of the Ruamahanga River and the associated Lake Wairarapa , as well as the long southern stretch of Palliser Bay . To the west of the plains rise the eastern slopes of the Remutaka Range , the crest of which forms the western boundary of the district, while the Aorangi Range lies to the south-east. The southernmost point of the North Island, Cape Palliser ,

94-554: 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

141-445: 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

188-402: A population density of 5.0 people per km. South Wairarapa District had a population of 11,811 in the 2023 New Zealand census , an increase of 1,236 people (11.7%) since the 2018 census , and an increase of 2,283 people (24.0%) since the 2013 census . There were 5,874 males, 5,886 females and 45 people of other genders in 4,953 dwellings. 3.8% of people identified as LGBTIQ+ . The median age

235-467: Is Martinborough ; it is the centre of a nationally important wine-producing area. It is expected that the number of people living in the district's urban areas will increase due to rising property prices in Wellington proper, and the proximity to transport links. South Wairarapa District covers 2,387.76 km (921.92 sq mi) and had an estimated population of 12,050 as of June 2024, with

282-546: 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

329-551: Is a rural railway station located in the Wairarapa , 5 km west of and serving Greytown , New Zealand . The station is located on the Wairarapa Line , 65.1 km (40.5 mi) north of Wellington and 25.9 km (16.1 mi) south of Masterton . The Wairarapa Connection serves the station several times daily with services to Wellington and Masterton. The station building has in recent years been restored by

376-406: 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

423-498: 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

470-460: 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

517-601: Is in the South Wairarapa. While it is predominantly rural, the South Wairarapa has three towns. The two largest towns, almost identical in population, are Greytown and Featherston . Greytown is where Arbor Day was first celebrated in New Zealand. The Fell Locomotive Museum in Featherston has a museum displaying the world's only Fell locomotive. The third-largest town and the seat of the district council

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564-565: 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

611-402: 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,

658-511: The Metlink public transport network for the Wellington region, passes through the district (which is served by the two stations of Featherston and Woodside ) and provides a faster method of transport into the city than the Remutaka pass road. Metlink buses also provide services to Greytown and Martinborough from the railway stations and Masterton . The South Wairarapa District Council is

705-762: The Woodside Station Preservation Society . The original survey for the Wairarapa Line, completed in 1876, considered two routes for the line between Featherston and Masterton: the Central route and the Western route. Despite the protestations of the residents of Greytown, the Western route was chosen due to concerns about the possibility of flooding north of Greytown, which meant that the line bypassed Greytown and passed through Woodside instead. Woodside opened on 14 May 1880 with

752-557: 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

799-747: 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

846-560: 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

893-400: 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

940-511: 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

987-421: The census question. Of those at least 15 years old, 2,031 (20.8%) people had a bachelor's or higher degree, 5,013 (51.3%) had a post-high school certificate or diploma, and 2,010 (20.6%) people exclusively held high school qualifications. The median income was $ 42,800, compared with $ 41,500 nationally. 1,569 people (16.1%) earned over $ 100,000 compared to 12.1% nationally. The employment status of those at least 15

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1034-467: 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

1081-567: The extension of the line from Featherston. Until the line from Woodside to Masterton was completed and opened in November of that year, Woodside was the northern terminus of the Wairarapa Line and was operated by the Public Works Department, initially with two mixed trains between Greytown and Wellington each day. The amenities at Woodside initially consisted of a station building and stationmaster's house. The station building

1128-472: 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

1175-448: 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

1222-462: 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

1269-599: 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 ,

1316-447: 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. Woodside railway station, New Zealand Woodside railway station

1363-465: 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

1410-448: 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

1457-417: 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

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1504-457: 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

1551-465: The main line yard was removed, and the station building relocated to a new platform on the western side of the main line. A new crossing loop was installed, and the branch sidings reconfigured. In 1954 the Greytown station building was relocated to Woodside and modified to serve as a goods shed. It is now disused and the loop and sidings have been removed. With the opening of the line to Masterton and

1598-617: 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

1645-762: 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

1692-733: The reversion of the line to Greytown to branch-line status, Woodside became known as Woodside Junction until the closure of the Greytown Branch in 1953: the platform name board read "Woodside Junction. Change here for Greytown." A Wairarapa train was struck by a tree branch on 17 September 2019 near the Waiohine Bridge, but the driver continued and stopped at Woodside Station. There are five Metlink Wairarapa Connection trains both ways on Monday to Thursday, six on Friday and two each way on Saturday and Sunday. A shuttle bus service to Greytown, Route 204, connects with trains. It

1739-580: 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

1786-511: 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

1833-418: 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

1880-408: 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

1927-459: 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

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1974-718: The territorial authority responsible for the area. The council consists of nine councillors; the current mayor is Martin Connelly . The three towns also have their own community boards. Floodplain A floodplain or flood plain or bottomlands 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

2021-672: 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

2068-561: Was 47.5 years (compared with 38.1 years nationally). There were 2,037 people (17.2%) aged under 15 years, 1,458 (12.3%) aged 15 to 29, 5,580 (47.2%) aged 30 to 64, and 2,736 (23.2%) aged 65 or older. People could identify as more than one ethnicity. The results were 90.1% European ( Pākehā ); 15.4% Māori ; 2.7% Pasifika ; 3.5% Asian ; 0.7% Middle Eastern, Latin American and African New Zealanders (MELAA); and 2.5% other, which includes people giving their ethnicity as "New Zealander". English

2115-481: Was on an island platform between the main line and the Greytown Branch , with the junction at the southern end of the platform. There was road access from north of the platform. The branch (eastern) side had two loops, with capacities of 18 and 11 wagons, while on the main line (western) side there were two loops with capacities of 44 and 35 wagons. Some years after the closure of the Greytown Branch in 1953

2162-542: Was spoken by 97.7%, Māori language by 2.7%, Samoan by 0.6% and other languages by 7.8%. No language could be spoken by 1.8% (e.g. too young to talk). New Zealand Sign Language was known by 0.4%. The percentage of people born overseas was 18.6, compared with 28.8% nationally. Religious affiliations were 27.5% Christian , 0.4% Hindu , 0.6% Māori religious beliefs , 0.6% Buddhist , 0.5% New Age , 0.2% Jewish , and 1.0% other religions. People who answered that they had no religion were 61.6%, and 7.6% of people did not answer

2209-452: Was that 4,851 (49.6%) people were employed full-time, 1,554 (15.9%) were part-time, and 186 (1.9%) were unemployed. Because of South Wairarapa's proximity to the capital city of New Zealand, Wellington, there are close links between the two areas. For example, some people live in South Wairarapa and commute to Wellington each day to work; others live and work in Wellington while spending weekends in South Wairarapa. The Wairarapa Line , part of

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