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50-655: The forest area has some of the highest rainfall rates in Kenya. Mau Forest is the largest drainage basin in Kenya. Numerous rivers originate from the forest, including the Southern Ewaso Ng'iro , Sondu River , Mara River and Njoro River . These rivers feed Lake Victoria , Lake Nakuru and Lake Natron . The western slopes of the Mau Escarpment are covered by the Mau Forest. Typical tree species in

100-484: A sink , which may be a permanent lake, a dry lake , or a point where surface water is lost underground . Drainage basins are similar but not identical to hydrologic units , which are drainage areas delineated so as to nest into a multi-level hierarchical drainage system . Hydrologic units are defined to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units but not all hydrologic units are drainage basins. About 48.71% of

150-581: A topographical prominence requirement, typically 100 feet (30.5 m) or 500 feet (152.4 m). In practice, mountains in Scotland are frequently referred to as "hills" no matter what their height, as reflected in names such as the Cuillin Hills and the Torridon Hills . In Wales, the distinction is more a term of land use and appearance and has nothing to do with height. For a while,

200-414: A watershed , though in other English-speaking places, "watershed" is used only in its original sense, that of the drainage divide line. A drainage basin's boundaries are determined by watershed delineation , a common task in environmental engineering and science. In a closed drainage basin, or endorheic basin , rather than flowing to the ocean, water converges toward the interior of the basin, known as

250-454: A drainage basin, and there are different ways to interpret that data. In the unlikely event that the gauges are many and evenly distributed over an area of uniform precipitation, using the arithmetic mean method will give good results. In the Thiessen polygon method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for

300-540: A drainage boundary is referred to as watershed delineation . Finding the area and extent of a drainage basin is an important step in many areas of science and engineering. Most of the water that discharges from the basin outlet originated as precipitation falling on the basin. A portion of the water that enters the groundwater system beneath the drainage basin may flow towards the outlet of another drainage basin because groundwater flow directions do not always match those of their overlying drainage network. Measurement of

350-436: A hill). The rounded peaks of hills results from the diffusive movement of soil and regolith covering the hill, a process known as downhill creep . Various names may be used to describe types of hills, based on appearance and method of formation. Many such names originated in one geographical region to describe a type of hill formation particular to that region, though the names are often adopted by geologists and used in

400-548: A limit of 2,000 feet (610 m) and Whittow states "Some authorities regard eminences above 600 m (1,969 ft) as mountains, those below being referred to as hills." Today, a mountain is usually defined in the UK and Ireland as any summit at least 2,000 feet or 610 meters high, while the UK government's Countryside and Rights of Way Act 2000 defined mountainous areas (for the purposes of open access legislation) as areas above 600 meters (1,969 feet). Some definitions include

450-536: A much smaller force entrenched on the hill top. Battles for the possession of high ground have often resulted in heavy casualties to both sides, such as the 1969 Battle of Hamburger Hill during the Vietnam War , the Battle of Stalingrad and Battle of Peleliu during World War II , and the 1969 Kargil War between India and Pakistan. The Great Wall of China is an enduring example of hilltop fortification. It

500-676: A resettlement scheme. On July 15, 2008, the then Prime Minister, Raila Odinga issued an order that the evictions be implemented by October 2008 in order to protect the forest from destruction. The order has been opposed by number of Rift Valley area politicians, led by Isaac Ruto . Some politicians, led by Minister of Agriculture William Ruto , propose that if evictions are implemented, the government should allocate them land elsewhere. The evictions began in November 2009. Some prominent people are set to lose their land, including family members of former president Daniel arap Moi . Also under threat

550-454: A wider geographical context. These include: Many settlements were originally built on hills, either to avoid floods (particularly if they were near a large body of water), for defense (since they offer a good view of the surrounding land and require would-be attackers to fight uphill), or to avoid densely forested areas. For example, Ancient Rome was built on seven hills , helping to protect it from invaders. Some settlements, particularly in

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600-545: Is a small hill. Other words include knoll and (in Scotland, Northern Ireland and northern England) its variant, knowe. Artificial hills may be referred to by a variety of technical names, including mound and tumulus . Hills may form through geomorphic phenomena : faulting , erosion of larger landforms such as mountains and movement and deposition of sediment by glaciers (notably moraines and drumlins or by erosion exposing solid rock which then weathers down into

650-564: Is popular in hilly areas such as the English Peak District and the Scottish Highlands . Many hills are categorized according to relative height or other criteria and feature on lists named after mountaineers, such as Munros (Scotland) and Wainwrights (England). Specific activities such as " peak bagging " (or "Munro bagging") involve climbing hills on these lists with the aim of eventually climbing every hill on

700-487: Is referred to as " watershed management ". In Brazil , the National Policy of Water Resources, regulated by Act n° 9.433 of 1997, establishes the drainage basin as the territorial division of Brazilian water management. When a river basin crosses at least one political border, either a border within a nation or an international boundary, it is identified as a transboundary river . Management of such basins becomes

750-447: Is separated from adjacent basins by a perimeter, the drainage divide , made up of a succession of elevated features, such as ridges and hills . A basin may consist of smaller basins that merge at river confluences , forming a hierarchical pattern . Other terms for a drainage basin are catchment area , catchment basin , drainage area , river basin , water basin , and impluvium . In North America, they are commonly called

800-465: Is sustainable. However, due to immigration from other ethnic groups, large parts of the forest area have been cleared for settlement. Human activities, especially logging , have led to deforestation of more than a quarter of the area since 1973. This is due to the increased charcoal trade in places like Narok town and the supply of logs to saw mills in Baringo , Nakuru and Narok counties. In 2008,

850-614: Is the Dead Sea . Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. For example, the English crown gave the Hudson's Bay Company a monopoly on the fur trade in the entire Hudson Bay basin, an area called Rupert's Land . Bioregional political organization today includes agreements of states (e.g., international treaties and, within

900-476: Is the Kiptagich Tea Factory owned by former president Moi. 0°36′35″S 35°44′08″E  /  0.60972°S 35.73556°E  / -0.60972; 35.73556 Drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth , or flows into another body of water , such as a lake or ocean . A basin

950-713: The African Great Lakes , the interiors of Australia and the Arabian Peninsula , and parts in Mexico and the Andes . Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins. In endorheic bodies of water where evaporation is the primary means of water loss, the water is typically more saline than the oceans. An extreme example of this

1000-828: The Continental Divide , northern Alaska and parts of North Dakota , South Dakota , Minnesota , and Montana in the United States, the north shore of the Scandinavian peninsula in Europe, central and northern Russia, and parts of Kazakhstan and Mongolia in Asia , which totals to about 17% of the world's land. Just over 13% of the land in the world drains to the Pacific Ocean . Its basin includes much of China, eastern and southeastern Russia, Japan,

1050-714: The Korean Peninsula , most of Indochina, Indonesia and Malaysia, the Philippines, all of the Pacific Islands , the northeast coast of Australia , and Canada and the United States west of the Continental Divide (including most of Alaska), as well as western Central America and South America west of the Andes. The Indian Ocean 's drainage basin also comprises about 13% of Earth's land. It drains

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1100-472: The groundwater . A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. Hill A hill is a landform that extends above the surrounding terrain. It often has a distinct summit , and is usually applied to peaks which are above elevation compared to the relative landmass, though not as prominent as mountains . Hills fall under

1150-596: The 1775 Battle of Bunker Hill (which was actually fought on Breed's Hill ) in the American War of Independence ; and Cemetery Hill and Culp's Hill in the 1863 Battle of Gettysburg , the turning point of the American Civil War . The Battle of San Juan Hill in the 1898 Spanish–American War won the Americans control of Santiago de Cuba but only after suffering from heavy casualties inflicted by

1200-507: The Mau Forest include Aningeria adolfi-friederici , Strombosia scheffleri , and Polyscias kikuyuensis . Olea capensis , Prunus africana , Albizia gummifera , and Podocarpus milanjianus are also found there. Endemic bird species in the area include Hartlaub's turaco ( Tauraco hartlaubi ), Hunter's cisticola ( Cisticola hunteri ) and Jackson's spurfowl ( Pternistis jacksoni ). The forest has been traditionally inhabited by Ogiek people, whose hunter-gatherer lifestyle

1250-528: The Middle East, are located on artificial hills consisting of debris (particularly mudbricks ) that has accumulated over many generations. Such a location is known as a " tell ". In Northern Europe , many ancient monuments are sited in heaps. Some of these are defensive structures (such as the hillforts of the Iron Age ), but others appear to have hardly any significance. In Britain, many churches at

1300-460: The US defined a mountain as being 1,000 feet (304.8 m) or more tall. Any similar landform lower than this height was considered a hill. The United States Geological Survey , however, has concluded that these terms do not in fact have technical definitions in the US. The Great Soviet Encyclopedia defined "hill" as an upland with a relative height of up to 200 m (660 ft). A hillock

1350-575: The US, interstate compacts ) or other political entities in a particular drainage basin to manage the body or bodies of water into which it drains. Examples of such interstate compacts are the Great Lakes Commission and the Tahoe Regional Planning Agency . In hydrology , the drainage basin is a logical unit of focus for studying the movement of water within the hydrological cycle . The process of finding

1400-406: The basin, it can form tributaries that change the structure of the land. There are three different main types, which are affected by the rocks and ground underneath. Rock that is quick to erode forms dendritic patterns, and these are seen most often. The two other types of patterns that form are trellis patterns and rectangular patterns. Rain gauge data is used to measure total precipitation over

1450-474: The category of slope landforms . The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally considered to be not as tall, or as steep as a mountain. Geographers historically regarded mountains as hills greater than 1,000 feet (304.8 meters) above sea level . In contrast, hillwalkers have tended to regard mountains as peaks 2,000 feet (610 m) above sea level. The Oxford English Dictionary also suggests

1500-418: The city's fog and civil engineering projects today famous as tourist attractions such as the cable cars and Lombard Street . Hills provide important advantages to an army that controls their heights, giving them an elevated view and firing position and forcing an opposing army to charge uphill to attack a fort or other position. They may also conceal forces behind them, allowing a force to lie in wait on

1550-510: The crest of a hill, using that crest for cover, and firing on unsuspecting attackers as they broach the hilltop. As a result, conventional military strategies often demand possession of high ground. Because of their strategic and tactical values, hills have been the site of many notable battles, such as the Battle of Alesia in 52 BC and the first recorded military conflict in Scotland, the Battle of Mons Graupius in AD 83. Modern era conflicts include

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1600-430: The discharge of water from a basin may be made by a stream gauge located at the basin's outlet. Depending on the conditions of the drainage basin, as rainfall occurs some of it seeps directly into the ground. This water will either remain underground, slowly making its way downhill and eventually reaching the basin, or it will permeate deeper into the soil and consolidate into groundwater aquifers. As water flows through

1650-441: The drainage area is dependent on the soil type. Certain soil types such as sandy soils are very free-draining, and rainfall on sandy soil is likely to be absorbed by the ground. However, soils containing clay can be almost impermeable and therefore rainfall on clay soils will run off and contribute to flood volumes. After prolonged rainfall even free-draining soils can become saturated , meaning that any further rainfall will reach

1700-697: The drainage basin to the mouth, and may accumulate there, disturbing the natural mineral balance. This can cause eutrophication where plant growth is accelerated by the additional material. Because drainage basins are coherent entities in a hydrological sense, it has become common to manage water resources on the basis of individual basins. In the U.S. state of Minnesota , governmental entities that perform this function are called " watershed districts ". In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called conservation authorities . In North America, this function

1750-857: The eastern coast of Africa, the coasts of the Red Sea and the Persian Gulf , the Indian subcontinent , Burma, and most parts of Australia . The five largest river basins (by area), from largest to smallest, are those of the Amazon (7 million km ), the Congo (4 million km ), the Nile (3.4 million km ), the Mississippi (3.22 million km ), and the Río de la Plata (3.17 million km ). The three rivers that drain

1800-583: The greatest portion of western Sub-Saharan Africa , as well as Western Sahara and part of Morocco . The two major mediterranean seas of the world also flow to the Atlantic. The Caribbean Sea and Gulf of Mexico basin includes most of the U.S. interior between the Appalachian and Rocky Mountains , a small part of the Canadian provinces of Alberta and Saskatchewan , eastern Central America ,

1850-435: The ground and along rivers it can pick up nutrients , sediment , and pollutants . With the water, they are transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water body . Modern use of artificial fertilizers , containing nitrogen (as nitrates ), phosphorus , and potassium , has affected the mouths of drainage basins. The minerals are carried by

1900-781: The ground at its terminus, the area can go by several names, such playa, salt flat, dry lake , or alkali sink . The largest endorheic basins are in Central Asia , including the Caspian Sea , the Aral Sea , and numerous smaller lakes. Other endorheic regions include the Great Basin in the United States, much of the Sahara Desert , the drainage basin of the Okavango River ( Kalahari Basin ), highlands near

1950-779: The inauguration of the Sondu-Miriu hydro power plant was postponed due to low water levels, that are said to be resulting from the destruction of the Mau Forest. In the summer of 2008 there was a political row over resettlement of people, who had been allocated land there during the KANU era during the 1980s and 1990s. Some of the settlers are famed politicians, like Franklin Bett and Zakayo Cheruiyot . In 2004 Paul Ndung’u released "Ndungu Report", which listed these land allocations, terming them illegal and recommended revocation of them. Some evictions were implemented between 2004 and 2006, without

2000-639: The islands of the Caribbean and the Gulf, and a small part of northern South America. The Mediterranean Sea basin, with the Black Sea , includes much of North Africa , east-central Africa (through the Nile River ), Southern , Central, and Eastern Europe , Turkey , and the coastal areas of Israel , Lebanon , and Syria . The Arctic Ocean drains most of Western Canada and Northern Canada east of

2050-514: The most water, from most to least, are the Amazon, Ganges , and Congo rivers. Endorheic basin are inland basins that do not drain to an ocean. Endorheic basins cover around 18% of the Earth's land. Some endorheic basins drain to an Endorheic lake or Inland sea . Many of these lakes are ephemeral or vary dramatically in size depending on climate and inflow. If water evaporates or infiltrates into

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2100-418: The rainfall on the area of land included in its polygon. These polygons are made by drawing lines between gauges, then making perpendicular bisectors of those lines form the polygons. The isohyetal method involves contours of equal precipitation are drawn over the gauges on a map. Calculating the area between these curves and adding up the volume of water is time-consuming. Isochrone maps can be used to show

2150-631: The responsibility of the countries sharing it. Nile Basin Initiative , OMVS for Senegal River , Mekong River Commission are a few examples of arrangements involving management of shared river basins. Management of shared drainage basins is also seen as a way to build lasting peaceful relationships among countries. The catchment is the most significant factor determining the amount or likelihood of flooding . Catchment factors are: topography , shape, size, soil type, and land use (paved or roofed areas). Catchment topography and shape determine

2200-461: The river rather than being absorbed by the ground. If the surface is impermeable the precipitation will create surface run-off which will lead to higher risk of flooding; if the ground is permeable, the precipitation will infiltrate the soil. Land use can contribute to the volume of water reaching the river, in a similar way to clay soils. For example, rainfall on roofs, pavements , and roads will be collected by rivers with almost no absorption into

2250-418: The speed with which the runoff reaches a river. A long thin catchment will take longer to drain than a circular catchment. Size will help determine the amount of water reaching the river, as the larger the catchment the greater the potential for flooding. It is also determined on the basis of length and width of the drainage basin. Soil type will help determine how much water reaches the river. The runoff from

2300-415: The time taken for rain to reach the river, while catchment size, soil type, and development determine the amount of water to reach the river. Generally, topography plays a big part in how fast runoff will reach a river. Rain that falls in steep mountainous areas will reach the primary river in the drainage basin faster than flat or lightly sloping areas (e.g., > 1% gradient). Shape will contribute to

2350-477: The time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall. Drainage basins are the principal hydrologic unit considered in fluvial geomorphology . A drainage basin is the source for water and sediment that moves from higher elevation through the river system to lower elevations as they reshape the channel forms. Drainage basins are important in ecology . As water flows over

2400-500: The tops of hills are thought to have been built on the sites of earlier pagan holy places. The Washington National Cathedral in Washington, D.C. has followed this tradition and was built on the highest hill in that city. Some cities' hills are culturally significant in their foundation, defense, and history. In addition to Rome, hills have played a prominent role in the history of San Francisco , with its hills being central to

2450-673: The world's land drains to the Atlantic Ocean . In North America , surface water drains to the Atlantic via the Saint Lawrence River and Great Lakes basins, the Eastern Seaboard of the United States, the Canadian Maritimes , and most of Newfoundland and Labrador . Nearly all of South America east of the Andes also drains to the Atlantic, as does most of Western and Central Europe and

2500-469: Was built on hilltops to help defend against invaders from the north, such as Mongols . Hillwalking is a British English term for a form of hiking which involves the ascent of hills. The activity is usually distinguished from mountaineering as it does not involve ropes or technically difficult rock climbing , although the terms mountain and hill are often used interchangeably in Britain. Hillwalking

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