Walker Lake (Northwest Arctic, Alaska)
Walker Lake is the source of the Kobuk River in northwestern Alaska. The lake is located near the easternmost part of Northwest Arctic Borough, deep in the remote interior of northern Alaska. Explored during an expedition led by John C. Cantwell in 1885, under the authority of the Revenue Marine. Known as "Big Fish Lake", Inupiaq legend in the area told of giant, ferocious fish that inhabited the waters. An attempt by a native with the Cantwell expedition to catch one of these giant fish involved a hook made of an entire set of reindeer antlers baited with a whole goose. In 1968, Walker Lake, was designated as a National Natural Landmark by the National Park Service. Sherwood, M.. Exploration of Alaska: 1865-1900. New Haven and London: Yale University Press. List of lakes of Alaska List of National Natural Landmarks List of reported lake monsters
United States Congress
The United States Congress is the bicameral legislature of the Federal Government of the United States. The legislature consists of two chambers: the House of the Senate; the Congress meets in the United States Capitol in Washington, D. C.. Both senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a gubernatorial appointment. Congress has 535 voting members: 100 senators; the House of Representatives has six non-voting members representing Puerto Rico, American Samoa, the Northern Mariana Islands, the U. S. Virgin Islands, the District of Columbia in addition to its 435 voting members. Although they cannot vote in the full house, these members can address the house and vote in congressional committees, introduce legislation; the members of the House of Representatives serve two-year terms representing the people of a single constituency, known as a "district". Congressional districts are apportioned to states by population using the United States Census results, provided that each state has at least one congressional representative.
Each state, regardless of population or size, has two senators. There are 100 senators representing the 50 states; each senator is elected at-large in their state for a six-year term, with terms staggered, so every two years one-third of the Senate is up for election. To be eligible for election, a candidate must be aged at least 25 or 30, have been a citizen of the United States for seven or nine years, be an inhabitant of the state which they represent; the Congress was created by the Constitution of the United States and first met in 1789, replacing in its legislative function the Congress of the Confederation. Although not mandated, in practice since the 19th century, Congress members are affiliated with the Republican Party or with the Democratic Party and only with a third party or independents. Article One of the United States Constitution states, "All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives."
The House and Senate are equal partners in the legislative process—legislation cannot be enacted without the consent of both chambers. However, the Constitution grants each chamber some unique powers; the Senate ratifies treaties and approves presidential appointments while the House initiates revenue-raising bills. The House initiates impeachment cases. A two-thirds vote of the Senate is required before an impeached person can be forcibly removed from office; the term Congress can refer to a particular meeting of the legislature. A Congress covers two years; the Congress ends on the third day of January of every odd-numbered year. Members of the Senate are referred to as senators. Scholar and representative Lee H. Hamilton asserted that the "historic mission of Congress has been to maintain freedom" and insisted it was a "driving force in American government" and a "remarkably resilient institution". Congress is the "heart and soul of our democracy", according to this view though legislators achieve the prestige or name recognition of presidents or Supreme Court justices.
One analyst argues that it is not a reactive institution but has played an active role in shaping government policy and is extraordinarily sensitive to public pressure. Several academics described Congress: Congress reflects us in all our strengths and all our weaknesses, it reflects our regional idiosyncrasies, our ethnic and racial diversity, our multitude of professions, our shadings of opinion on everything from the value of war to the war over values. Congress is the government's most representative body... Congress is charged with reconciling our many points of view on the great public policy issues of the day. Congress is changing and is in flux. In recent times, the American south and west have gained House seats according to demographic changes recorded by the census and includes more minorities and women although both groups are still underrepresented. While power balances among the different parts of government continue to change, the internal structure of Congress is important to understand along with its interactions with so-called intermediary institutions such as political parties, civic associations, interest groups, the mass media.
The Congress of the United States serves two distinct purposes that overlap: local representation to the federal government of a congressional district by representatives and a state's at-large representation to the federal government by senators. Most incumbents seek re-election, their historical likelihood of winning subsequent elections exceeds 90 percent; the historical records of the House of Representatives and the Senate are maintained by the Center for Legislative Archives, a part of the National Archives and Records Administration. Congress is directly responsible for the governing of the District of Columbia, the current seat of the federal government; the First Continental Congress was a gathering of representatives from twelve of the thirteen British Colonies in North America. On July 4, 1776, the Second Continental Congress adopted the Declaration of Independence, referring to the new nation as the "United States of America"; the Articles of Confederation in 1781 created the Congress of the Confederation, a
Dune
In physical geography, a dune is a hill of loose sand built by aeolian processes or the flow of water. Dunes occur in different sizes, formed by interaction with the flow of air or water. Most kinds of dunes are longer on the stoss side, where the sand is pushed up the dune, have a shorter "slip face" in the lee side; the valley or trough between dunes is called a slack. A "dune field" or erg is an area covered by extensive dunes. Dunes occur along some coasts; some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases, the dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated with ancient lake or sea beds. Dunes can form under the action of water flow, on sand or gravel beds of rivers and the sea-bed; the modern word "dune" came into English from French c.
1790, which in turn came from Middle Dutch dūne. Dunes are made of sand-sized particles, may consist of quartz, calcium carbonate, gypsum, or other materials; the upwind/upstream/upcurrent side of the dune is called the stoss side. Sand is pushed or bounces up the stoss side, slides down the lee side. A side of a dune that the sand has slid down is called a slip face; the Bagnold formula gives the speed. Five basic dune types are recognized: crescentic, star and parabolic. Dune areas may occur in three forms: simple and complex. Barchan dunes are crescent-shaped mounds which are wider than they are long; the lee-side slipfaces are on the concave sides of the dunes. These dunes form under winds that blow from one direction, they form separate crescents. When the sand supply is greater, they may merge into barchanoid ridges, transverse dunes; some types of crescentic dunes move more over desert surfaces than any other type of dune. A group of dunes moved more than 100 metres per year between 1954 and 1959 in China's Ningxia Province, similar speeds have been recorded in the Western Desert of Egypt.
The largest crescentic dunes on Earth, with mean crest-to-crest widths of more than three kilometres, are in China's Taklamakan Desert. See lunettes and parabolic dues, for dunes similar to crescent-shaped ones. Abundant barchan dunes may merge into barchanoid ridges, which grade into linear transverse dunes, so called because they lie transverse, or across, the wind direction, with the wind blowing perpendicular to the ridge crest. Seif dunes are linear dunes with two slip faces; the two slip faces make them sharp-crested. They are called seif dunes after the Arabic word for "sword", they may be more than 160 kilometres long, thus visible in satellite images. Seif dunes are associated with bidirectional winds; the long axes and ridges of these dunes extend along the resultant direction of sand movement. Some linear dunes merge to form Y-shaped compound dunes. Formation is debated. Bagnold, in The Physics of Blown Sand and Desert Dunes, suggested that some seif dunes form when a barchan dune moves into a bidirectional wind regime, one arm or wing of the crescent elongates.
Others suggest. In the sheltered troughs between developed seif dunes, barchans may be formed, because the wind is constrained to be unidirectional by the dunes. Seif dunes are common in the Sahara, they range up to 300 km in length. In the southern third of the Arabian Peninsula, a vast erg, called the Rub' al Khali or Empty Quarter, contains seif dunes that stretch for 200 km and reach heights of over 300 m. Linear loess hills known; these hills appear to have been formed during the last ice age under permafrost conditions dominated by sparse tundra vegetation. Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound, they tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally, they dominate the Grand Erg Oriental of the Sahara. In other deserts, they occur around the margins of the sand seas near topographic barriers. In the southeast Badain Jaran Desert of China, the star dunes are up to 500 metres tall and may be the tallest dunes on Earth.
Oval or circular mounds that lack a slipface. Dome dunes occur at the far upwind margins of sand seas. Fixed crescentic dunes that form on the leeward margins of playas and river valleys in arid and semiarid regions in response to the direction of prevailing winds, are known as lunettes, source-bordering dunes and clay dunes, they may be composed of clay, sand, or gypsum, eroded from the basin floor or shore, transported up the concave side of the dune, deposited on the convex side. Examples in Australia are up to 6.5 km long, 1 km wide, up to 50 metres high. They occur in southern and West Africa, in parts of the western United States Texas. U-shaped mounds of sand with convex noses trailed by elongated arms are parabolic dunes; these dunes are formed from blowout dunes where the erosion
Winter
Winter is the coldest season of the year in polar and temperate zones. It occurs before spring in each year. Winter is caused by the axis of the Earth. Different cultures define different dates as the start of winter, some use a definition based on weather; when it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, vice versa. In many regions, winter is associated with freezing temperatures; the moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value. The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice; the earliest sunset and latest sunrise dates outside the polar regions differ from the date of the winter solstice and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit. The English word "winter" comes from the Proto-Indo-European root "wend," relating to water.
The tilt of the Earth's axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23.44° to the plane of its orbit, causing different latitudes to directly face the Sun as the Earth moves through its orbit. This variation brings about seasons; when it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun. From the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun. During winter in either hemisphere, the lower altitude of the Sun causes the sunlight to hit the Earth at an oblique angle, thus a lower amount of solar radiation strikes the Earth per unit of surface area. Furthermore, the light must travel a longer distance through the atmosphere, allowing the atmosphere to dissipate more heat.
Compared with these effects, the effect of the changes in the distance of the Earth from the Sun is negligible. The manifestation of the meteorological winter in the northerly snow–prone latitudes is variable depending on elevation, position versus marine winds and the amount of precipitation. For instance, within Canada, Winnipeg on the Great Plains, a long way from the ocean, has a January high of −11.3 °C and a low of −21.4 °C. In comparison, Vancouver on the west coast with a marine influence from moderating Pacific winds has a January low of 1.4 °C with days well above freezing at 6.9 °C. Both places are at 49°N latitude, in the same western half of the continent. A similar but less extreme effect is found in Europe: in spite of their northerly latitude, the British Isles have not a single non-mountain weather station with a below-freezing mean January temperature. Meteorological reckoning is the method of measuring the winter season used by meteorologists based on "sensible weather patterns" for record keeping purposes, so the start of meteorological winter varies with latitude.
Winter is defined by meteorologists to be the three calendar months with the lowest average temperatures. This corresponds to the months of December and February in the Northern Hemisphere, June and August in the Southern Hemisphere; the coldest average temperatures of the season are experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Nighttime predominates in the winter season, in some regions winter has the highest rate of precipitation as well as prolonged dampness because of permanent snow cover or high precipitation rates coupled with low temperatures, precluding evaporation. Blizzards develop and cause many transportation delays. Diamond dust known as ice needles or ice crystals, forms at temperatures approaching −40 °C due to air with higher moisture from above mixing with colder, surface-based air, they are made of simple hexagonal ice crystals. The Swedish meteorological institute defines winter as when the daily mean temperatures are below 0 °C for five consecutive days.
According to the SMHI, winter in Scandinavia is more pronounced when Atlantic low-pressure systems take more southerly and northerly routes, leaving the path open for high-pressure systems to come in and cold temperatures to occur. As a result, the coldest January on record in Stockholm, in 1987, was the sunniest. Accumulations of snow and ice are associated with winter in the Northern Hemisphere, due to the large land masses there. In the Southern Hemisphere, the more maritime climate and the relative lack of land south of 40°S makes the winters milder. In this region, snow occurs every year in elevated regions such as the Andes, the Great Dividing Range in Australia, the mountains of New Zealand, occurs in the southerly Patagonia region of South Argentina. Snow occurs year-round in Antarctica. In the Northern Hemisphere, some authorities define the period of winter based on astronomical fixed points, regardless of weather conditions. In one version of this definition, winter begins at the winter solstice and ends at the ver
Seattle
Seattle is a seaport city on the West Coast of the United States. It is the seat of Washington. With an estimated 730,000 residents as of 2018, Seattle is the largest city in both the state of Washington and the Pacific Northwest region of North America. According to U. S. Census data released in 2018, the Seattle metropolitan area’s population stands at 3.87 million, ranks as the 15th largest in the United States. In July 2013, it was the fastest-growing major city in the United States and remained in the Top 5 in May 2015 with an annual growth rate of 2.1%. In July 2016, Seattle was again the fastest-growing major U. S. city, with a 3.1% annual growth rate. Seattle is the northernmost large city in the United States; the city is situated on an isthmus between Puget Sound and Lake Washington, about 100 miles south of the Canada–United States border. A major gateway for trade with Asia, Seattle is the fourth-largest port in North America in terms of container handling as of 2015; the Seattle area was inhabited by Native Americans for at least 4,000 years before the first permanent European settlers.
Arthur A. Denny and his group of travelers, subsequently known as the Denny Party, arrived from Illinois via Portland, Oregon, on the schooner Exact at Alki Point on November 13, 1851; the settlement was moved to the eastern shore of Elliott Bay and named "Seattle" in 1852, in honor of Chief Si'ahl of the local Duwamish and Suquamish tribes. Today, Seattle has high populations of Native, Scandinavian and Asian Americans, as well as a thriving LGBT community that ranks 6th in the United States for population. Logging was Seattle's first major industry, but by the late 19th century, the city had become a commercial and shipbuilding center as a gateway to Alaska during the Klondike Gold Rush. Growth after World War II was due to the local Boeing company, which established Seattle as a center for aircraft manufacturing; the Seattle area developed into a technology center from the 1980s onwards with companies like Microsoft becoming established in the region. Internet retailer Amazon was founded in Seattle in 1994, major airline Alaska Airlines is based in SeaTac, serving Seattle's international airport, Seattle–Tacoma International Airport.
The stream of new software and Internet companies led to an economic revival, which increased the city's population by 50,000 between 1990 and 2000. Owing to its increasing population in the 21st century and the state of Washington have some of the highest minimum wages in the country, at $15 per hour for smaller businesses and $16 for the city's largest employers. Seattle has a noteworthy musical history. From 1918 to 1951, nearly two dozen jazz nightclubs existed along Jackson Street, from the current Chinatown/International District to the Central District; the jazz scene nurtured the early careers of Ray Charles, Quincy Jones, Ernestine Anderson, others. Seattle is the birthplace of rock musician Jimi Hendrix, as well as the origin of the bands Nirvana, Pearl Jam, Alice in Chains, Foo Fighters and the alternative rock movement grunge. Archaeological excavations suggest that Native Americans have inhabited the Seattle area for at least 4,000 years. By the time the first European settlers arrived, the people occupied at least seventeen villages in the areas around Elliott Bay.
The first European to visit the Seattle area was George Vancouver, in May 1792 during his 1791–95 expedition to chart the Pacific Northwest. In 1851, a large party led by Luther Collins made a location on land at the mouth of the Duwamish River. Thirteen days members of the Collins Party on the way to their claim passed three scouts of the Denny Party. Members of the Denny Party claimed land on Alki Point on September 28, 1851; the rest of the Denny Party set sail from Portland and landed on Alki point during a rainstorm on November 13, 1851. After a difficult winter, most of the Denny Party relocated across Elliott Bay and claimed land a second time at the site of present-day Pioneer Square, naming this new settlement Duwamps. Charles Terry and John Low remained at the original landing location and reestablished their old land claim and called it "New York", but renamed "New York Alki" in April 1853, from a Chinook word meaning "by and by" or "someday". For the next few years, New York Alki and Duwamps competed for dominance, but in time Alki was abandoned and its residents moved across the bay to join the rest of the settlers.
David Swinson "Doc" Maynard, one of the founders of Duwamps, was the primary advocate to name the settlement after Chief Seattle of the Duwamish and Suquamish tribes. The name "Seattle" appears on official Washington Territory papers dated May 23, 1853, when the first plats for the village were filed. In 1855, nominal land settlements were established. On January 14, 1865, the Legislature of Territorial Washington incorporated the Town of Seattle with a board of trustees managing the city; the Town of Seattle was disincorporated on January 18, 1867, remained a mere precinct of King County until late 1869, when a new petition was filed and the city was re-incorporated December 2, 1869, with a mayor–council government. The corporate seal of the City of Seattle carries the date "1869" and a likeness of Chief Sealth in left profile. Seattle has a history of boom-and-bust cycles, like many other cities near areas of extensive natural and mineral resources. Seattle has risen several times economically gone into precipitous decline, but it has used those periods to rebuild solid infrastructure
United States Revenue Cutter Service
The United States Revenue Cutter Service was established by an act of Congress on 4 August 1790 as the Revenue-Marine upon the recommendation of Secretary of the Treasury Alexander Hamilton to serve as an armed customs enforcement service. As time passed, the service gained missions either voluntarily or by legislation, including those of a military nature, it was referred to as the Revenue-Marine until 31 July 1894, when it was renamed the Revenue Cutter Service. The Revenue Cutter Service operated under the authority of the U. S. Department of the Treasury. On 28 January 1915, the service was merged by an act of Congress with the United States Life-Saving Service to form the United States Coast Guard. After the American Revolutionary War the new United States was struggling to stay afloat financially. National income was needed, the government determined that a great deal of this income would come from tariffs on imports; because of rampant smuggling, the need was immediate for strong enforcement of tariff laws.
On 4 August 1790, the United States Congress, urged on by Secretary of the Treasury Alexander Hamilton, created the Revenue-Marine renamed the Revenue Cutter Service by act of 31 July 1894. A cutter vessel is a small or medium-sized boat or sailing ship, built for speed and with a shallow draught. While some larger cutters had two or three masts, many cutters had only one, located more centrally on the ship than was typical of larger vessels. In modern times, any naval ship built for speed and agility is still referred to as a cutter. Under the enabling legislation that authorized the Revenue-Marine, the "System of Cutters", consisting of ten vessels were ordered and constructed. Two cutters were to be assigned to "the coasts of New Hampshire. On 21 March 1791 the first seven masters were commissioned by President George Washington. Among those commissioned were Hopley Yeaton and John Foster Williams of Massachusetts, Jonathan Maltbie of Connecticut, Patrick Dennis of New York, James Montgomery of Pennsylvania, Simon Gross of Maryland, Richard Taylor of Virginia.
William Cooke of North Carolina was commissioned on 25 April 1791, Robert Cochrane of South Carolina on 8 May 1791, 20 May 1791 John Howell of Georgia. Each cutter was constructed. Washington suggested to Hamilton that it would be advantageous to have each master supervise the construction of his own cutter. Hamilton's cost restrictions proved unrealistic for three of the new cutters, Massachusetts cost US$2,050, Scammel cost US$1,255, General Green cost over US$1,500; the same legislation that established the ten original cutters provided for the complement and pay scales of the crew of each vessel. Each vessel was provided with a master with pay set at $30 per month and three mates at $20, $16, $14, respectively. In addition each cutter was allowed four mariners at $8 apiece and two boys at $4. Between 1790 and 1798, the Revenue-Marine was the only armed maritime service of the United States, as the Navy had been disbanded; each cutter master was answerable to and received his sailing orders directly from the Collector of Customs of the port to which his ship was assigned.
All crew pay, requests for supplies, arrangements for repairs to the cutter, mission-specific tasking came directly from the port's Customs House. After the Slave Trade Act of 1794 was enacted, the Revenue-Marine began intercepting slave ships illegally importing slaves into the United States; this was the case from 1791 to 1871, except for the period 1843-49, when oversight was vested in the Revenue Marine Division of the Treasury Department. Standing orders for individual cutters were stated in general terms, allowing captains to exercise their discretion and judgment to the fullest. Captains had far-reaching authority "to seize vessels and goods in the cases in which they are liable to seizure for breaches of the Revenue laws" and to send inspection parties aboard vessels in port to ensure that cargo intended for export did not violate revenue laws, yet despite this considerable authority, Alexander Hamilton, in his first letter of instruction to the captains, had directed that they "will always keep in mind that their countrymen are freemen, and, as such, are impatient of everything that bears the least mark of a domineering spirit....
They will endeavor to overcome difficulties, if any are experienced, by a cool and temperate perseverance in their duty – by address and moderation, rather than by vehemence or violence." During the Quasi-War with France from 1798 to 1801, the U. S. Navy was formed and the Revenue-Marine fought alongside the Navy, capturing or assisting in the capture of 20 French ships. Ten of these were captured by the USRC Pickering. Revenue cutters were assigned to enforce the unpopular Embargo Act of 1807, which outlawed nearly all European trade and export, through American ports; the Act was enforced until it was repealed in 1808. In wartime, the Revenue Marine was placed under the command of the U. S. Navy, the cutters themselves were placed into military service. USRC Jefferson made the first American capture of an enemy ship in the War of 1812, the brig Patriot, in June 1812. On 3 August 1812, the boats of the British frigates Maidstone and Spartan captured the 6-gun revenue cutter Commodore
Erosion
In earth science, erosion is the action of surface processes that removes soil, rock, or dissolved material from one location on the Earth's crust, transports it to another location. This natural process is caused by the dynamic activity of erosive agents, that is, ice, air, plants and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind erosion, zoogenic erosion, anthropogenic erosion; the particulate breakdown of rock or soil into clastic sediment is referred to as physical or mechanical erosion. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Natural rates of erosion are controlled by the action of geological weathering geomorphic drivers, such as rainfall; the rates at which such processes act control. Physical erosion proceeds fastest on steeply sloping surfaces, rates may be sensitive to some climatically-controlled properties including amounts of water supplied, wind speed, wave fetch, or atmospheric temperature.
Feedbacks are possible between rates of erosion and the amount of eroded material, carried by, for example, a river or glacier. Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, which control the arrival and emplacement of material at a new location. While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally. At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the natural rate of erosion in the region. Excessive erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses.
Water and wind erosion are the two primary causes of land degradation. Intensive agriculture, roads, anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion. However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils. Rainfall, the surface runoff which may result from rainfall, produces four main types of soil erosion: splash erosion, sheet erosion, rill erosion, gully erosion. Splash erosion is seen as the first and least severe stage in the soil erosion process, followed by sheet erosion rill erosion and gully erosion. In splash erosion, the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles; the distance these soil particles travel can be as much as 0.6 m vertically and 1.5 m horizontally on level ground. If the soil is saturated, or if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface runoff occurs.
If the runoff has sufficient flow energy, it will transport loosened soil particles down the slope. Sheet erosion is the transport of loosened soil particles by overland flow. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes. Where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are of the order of a few centimetres or less and along-channel slopes may be quite steep; this means that rills exhibit hydraulic physics different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when runoff water accumulates and flows in narrow channels during or after heavy rains or melting snow, removing soil to a considerable depth. Valley or stream erosion occurs with continued water flow along a linear feature; the erosion is both downward, deepening the valley, headward, extending the valley into the hillside, creating head cuts and steep banks.
In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is steep. When some base level is reached, the erosive activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain; the stream gradient becomes nearly flat, lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood when more and faster-moving water is available to carry a larger sediment load. In such processes, it is not the water alone
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