1.
San Fernando Valley
–
The San Fernando Valley is an urbanized valley located in Los Angeles County, California, defined by the mountains of the Transverse Ranges circling it. Home to 1.8 million people, it lies north of the larger, nearly two thirds of the valleys land area is part of the city of Los Angeles. The other incorporated cities in the valley are Glendale, Burbank, San Fernando, Hidden Hills, the Los Angeles River begins at the confluence of Calabasas Creek and Bell Creek, between Canoga Park High School and Owensmouth Ave. in Canoga Park. These creeks headwaters are in the Santa Monica Calabasas foothills, the Simi Hills Hidden Hills, Santa Susana Field Laboratory, the river flows eastward along the southern regions of the Valley. One of the rivers two unpaved sections can be found at the Sepulveda Basin, a seasonal river, the Tujunga Wash, drains much of the western facing San Gabriel Mountains and passes into and then through the Hansen Dam Recreation Center in Lake View Terrace. It flows south along the Verdugo Mountains through the communities of the valley to join the Los Angeles River in Studio City. Other notable tributaries of the river include Dayton Creek, Caballero Creek, Bull Creek, Pacoima Wash, the elevation of the floor of the valley varies from about 600 ft to 1,200 ft above sea level. Universal City, an enclave in the part of the valley, is unincorporated land housing the Universal Studios filming lot. Mulholland Drive, which runs along the ridgeline of the Santa Monica Mountains, in this Mediterranean climate, post-1790s European agriculture for the missions support consisted of grapes, figs, olives, and general garden crops. The San Fernando Valley contains five incorporated cities—Glendale, Burbank, San Fernando, Hidden Hills and Calabasas—and part of a sixth, Los Angeles, the unincorporated communities are governed by the County of Los Angeles. The Los Angeles city section of the valley is divided into seven city districts,2,3,4,5,6,7 and 12. Of the 95 neighborhood councils in the city,34 are in the valley, the valley is represented in the California State Legislature by seven members of the State Assembly and five members of the State Senate. The valley is divided into five congressional districts, the San Fernando Valley, for the most part, tends to support Democrats in state and national elections. This is especially true in the areas which include Sherman Oaks. The Los Angeles satellite administrative center for the valley, The Civic Center Van Nuys, is in Van Nuys. The area in and around the Van Nuys branch of Los Angeles City Hall is home to a station, municipal and superior courts. Northridge is home to California State University, Northridge, many branches of the Los Angeles Public Library are located in the valley. For independent libraries see Incorporated Cities in the Municipalities and districts list below, Los Angeles Police Department, Los Angeles County Sheriffs Department, and independent valley city departments
2.
California
–
California is the most populous state in the United States and the third most extensive by area. Located on the western coast of the U. S, California is bordered by the other U. S. states of Oregon, Nevada, and Arizona and shares an international border with the Mexican state of Baja California. Los Angeles is Californias most populous city, and the second largest after New York City. The Los Angeles Area and the San Francisco Bay Area are the nations second- and fifth-most populous urban regions, California also has the nations most populous county, Los Angeles County, and its largest county by area, San Bernardino County. The Central Valley, an agricultural area, dominates the states center. What is now California was first settled by various Native American tribes before being explored by a number of European expeditions during the 16th and 17th centuries, the Spanish Empire then claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its war for independence. The western portion of Alta California then was organized as the State of California, the California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom. If it were a country, California would be the 6th largest economy in the world, fifty-eight percent of the states economy is centered on finance, government, real estate services, technology, and professional, scientific and technical business services. Although it accounts for only 1.5 percent of the states economy, the story of Calafia is recorded in a 1510 work The Adventures of Esplandián, written as a sequel to Amadis de Gaula by Spanish adventure writer Garci Rodríguez de Montalvo. The kingdom of Queen Calafia, according to Montalvo, was said to be a land inhabited by griffins and other strange beasts. This conventional wisdom that California was an island, with maps drawn to reflect this belief, shortened forms of the states name include CA, Cal. Calif. and US-CA. Settled by successive waves of arrivals during the last 10,000 years, various estimates of the native population range from 100,000 to 300,000. The Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups also were diverse in their organization with bands, tribes, villages. Trade, intermarriage and military alliances fostered many social and economic relationships among the diverse groups, the first European effort to explore the coast as far north as the Russian River was a Spanish sailing expedition, led by Portuguese captain Juan Rodríguez Cabrillo, in 1542. Some 37 years later English explorer Francis Drake also explored and claimed a portion of the California coast in 1579. Spanish traders made unintended visits with the Manila galleons on their trips from the Philippines beginning in 1565
3.
Geographic coordinate system
–
A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position. A common choice of coordinates is latitude, longitude and elevation, to specify a location on a two-dimensional map requires a map projection. The invention of a coordinate system is generally credited to Eratosthenes of Cyrene. Ptolemy credited him with the adoption of longitude and latitude. Ptolemys 2nd-century Geography used the prime meridian but measured latitude from the equator instead. Mathematical cartography resumed in Europe following Maximus Planudes recovery of Ptolemys text a little before 1300, in 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, the Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911, the latitude of a point on Earths surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the equator, the north pole is 90° N, the south pole is 90° S. The 0° parallel of latitude is designated the equator, the plane of all geographic coordinate systems. The equator divides the globe into Northern and Southern Hemispheres, the longitude of a point on Earths surface is the angle east or west of a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses, which converge at the north and south poles, the prime meridian determines the proper Eastern and Western Hemispheres, although maps often divide these hemispheres further west in order to keep the Old World on a single side. The antipodal meridian of Greenwich is both 180°W and 180°E, the combination of these two components specifies the position of any location on the surface of Earth, without consideration of altitude or depth. The grid formed by lines of latitude and longitude is known as a graticule, the origin/zero point of this system is located in the Gulf of Guinea about 625 km south of Tema, Ghana. To completely specify a location of a feature on, in, or above Earth. Earth is not a sphere, but a shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the equator about 0. 3% larger than the radius measured through the poles, the shorter axis approximately coincides with the axis of rotation
4.
Flood control
–
Flood control refers to all methods used to reduce or prevent the detrimental effects of flood waters. Flood relief refers to methods used to reduce the effects of flood waters or high water levels, Flooding can be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce the supply of vegetation that can absorb rainfall. Periodic floods occur on many rivers, forming a region known as the flood plain. During times of rain, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation, some evaporates, floods occur when ponds, lakes, riverbeds, soil, and vegetation cannot absorb all the water. Water then runs off the land in quantities that cannot be carried within stream channels or retained in ponds, lakes. About 30 percent of all precipitation becomes runoff and that amount might be increased by water from melting snow, River flooding is often caused by heavy rain, sometimes increased by melting snow. A flood that rises rapidly, with little or no warning, is called a flash flood, flash floods usually result from intense rainfall over a relatively small area, or if the area was already saturated from previous precipitation. Even when rainfall is light, the shorelines of lakes. Coastal areas are flooded by unusually high tides, such as spring tides, especially when compounded by high winds. It damages property and endangers the lives of humans and other species, rapid water runoff causes soil erosion and concomitant sediment deposition elsewhere. The spawning grounds for fish and other wildlife habitats can become polluted or completely destroyed, some prolonged high floods can delay traffic in areas which lack elevated roadways. Floods can interfere with drainage and economical use of lands, such as interfering with farming, structural damage can occur in bridge abutments, bank lines, sewer lines, and other structures within floodways. Waterway navigation and hydroelectric power are often impaired, financial losses due to floods are typically millions of dollars each year, with the worst floods in recent U. S. history having cost billions of dollars. There are many effects of flooding on human settlements and economic activities. However, flooding can bring benefits, such as making soil more fertile, periodic flooding was essential to the well-being of ancient communities along the Tigris-Euphrates Rivers, the Nile River, the Indus River, the Ganges and the Yellow River, among others. The viability for hydrologically based renewable sources of energy is higher in flood-prone regions, some methods of flood control have been practiced since ancient times. These methods include planting vegetation to retain water, terracing hillsides to slow flow downhill. Other techniques include the construction of levees, lakes, dams, reservoirs and this is the method used for remote sensing the disasters
5.
United States Army Corps of Engineers
–
The United States Army Corps of Engineers, also sometimes shortened to CoE is a U. S. Although generally associated with dams, canals and flood protection in the United States, the Corps of Engineers provides outdoor recreation opportunities to the public, and provides 24% of U. S. hydropower capacity. The corps mission is to Deliver vital public and military engineering services, partnering in peace and war to strengthen our Nations security, energize the economy and their most visible missions include, Planning, designing, building, and operating locks and dams. Other civil engineering projects include flood control, beach nourishment, design and construction of flood protection systems through various federal mandates. Design and construction management of military facilities for the Army, Air Force, Army Reserve and Air Force Reserve and other Defense and Federal agencies. The history of United States Army Corps of Engineers can be traced back to 16 June 1775, colonel Richard Gridley became General George Washingtons first chief engineer, however, it was not until 1779 that Congress created a separate Corps of Engineers. One of its first tasks was to build fortifications near Boston at Bunker Hill, the first Corps of Engineers was mostly composed of French subjects who had been hired by General Washington from the service of Louis XVI. that the said Corps. Shall be stationed at West Point in the State of New York, until 1866, the superintendent of the United States Military Academy was always an officer of engineer. During the first half of the 19th century, West Point was the major and, for a while, the General Survey Act of 1824 authorized the use of Army engineers to survey road and canal routes. Separately authorized on 4 July 1838, the U. S and it was merged with the Corps of Engineers on 31 March 1863, at which point the Corps of Engineers also assumed the Lakes Survey District mission for the Great Lakes. In 1841, Congress created the Lake Survey, the survey, based in Detroit, Mich. was charged with conducting a hydrographical survey of the Northern and Northwestern Lakes and preparing and publishing nautical charts and other navigation aids. The Lake Survey published its first charts in 1852, in the mid-19th century, Corps of Engineers officers ran Lighthouse Districts in tandem with U. S. Naval officers. The Army Corps of Engineers played a significant role in the American Civil War, many of the men who would serve in the top leadership in this institution were West Point graduates who rose to military fame and power during the Civil War. Some of these men were Union Generals George McClellan, Henry Halleck, George Meade, and Confederate generals Robert E. Lee, Joseph Johnston, the versatility of officers in the Army Corps of Engineers contributed to the success of numerous missions throughout the Civil War. They were responsible for building pontoon and railroad bridges, forts and batteries, the destruction of supply lines. The Army Corps of Engineers served as a function in making the war effort logistically feasible. This method of building trenches was known as the zigzag pattern, from the beginning, many politicians wanted the Corps of Engineers to contribute to both military construction and works of a civil nature. During World War II the mission grew to more than 27,000 military, included were aircraft, tank assembly, and ammunition plants, camps for 5.3 million soldiers, depots, ports, and hospitals, as well as the Manhattan Project, and the Pentagon
6.
Los Angeles River
–
Several tributaries join the once free-flowing and frequently flooding river, forming alluvial flood plains along its banks. It now flows through a channel on a fixed course. Environmental groups and park advocates support the removal of concrete and the restoration of natural vegetation, portions of the river now have earthen bottoms and restored habitat. There are also plans for a series of parks along the rivers city frontage in Los Angeles, the Los Angeles River also flows through several Los Angeles County communities and has been featured in many Hollywood films. Before the opening of the Los Angeles Aqueduct, the river was the source of fresh water for the city. Although the Los Angeles region still gets some of its water from the river and other local sources, the river suffers pollution from agricultural and urban runoff. Fed primarily by rainwater and snowmelt, the Donald C, tillman Water Reclamation Plant in Van Nuys, and urban discharge, it is one of the few low-elevation perennial rivers in Southern California. This is helped by the channel, which limits absorption of water into the earth. Flow, while low in volume, can be extremely brisk even in summer. 1952°N118. 601838°W /34.1952. Bell Creek flows east from the Simi Hills, and Arroyo Calabasas flows north from the Santa Monica Mountains, from there the river flows east through a concrete flood control channel and very soon receives Browns Canyon Wash, which flows south from the Santa Susana Mountains. The river then bends south and receives Aliso Canyon Wash. The river then flows through the district of Winnetka, then Reseda and enters the Sepulveda Basin, as the river proceeds into the usually-dry reservoir, it spills out into a channel that is similar to its historical, unchannelized form. It crosses under Balboa Boulevard and then passes through the works of Sepulveda Dam,43 miles from the mouth. It flows again into a channel and crosses under Interstate 405 as it passes through Van Nuys, Sherman Oaks. Paralleling U. S. Here, the river begins to flow over a natural riverbed, paralleling Interstate 5 for the next few miles, the river runs by the eastern side of Griffith Park and the Harding-Wilson Golf Course. It passes Silver Lake Reservoir, which is to the right and it then receives the Arroyo Seco, another major tributary, from the left. The river flows south past the Mission Junction, a railroad yard on the left. It then makes a turn east and then turns southeast, flowing a few miles before it begins to parallel Interstate 710 near Maywood, Bell, Cudahy
7.
Thalweg
–
In geography and fluvial geomorphology, a thalweg or talweg is the line of lowest elevation within a valley or watercourse. Under international law, thalwegs can acquire special significance because disputed river borders are often deemed to run along the rivers thalweg, the word thalweg is of 19th-century German origin. The German word Thalweg is a noun that is built from the German elements Thal meaning valley. In hydrological and fluvial landforms, the thalweg is a line drawn to join the lowest points along the length of a stream bed or valley in its downward slope. The thalweg thus marks the direction of a watercourse. The term is sometimes used to refer to a subterranean stream that percolates under the surface. Slowing stream bed erosion by taking advantage of a thalweg helps stabilize running water sources, placing boulders along the thalweg in a running water source helps to protect the channels sedimentary erosion and deposit balance. This process of utilizing a thalweg to slow stream bed erosion was used in Meacham Creek in Umatilla, various states have also defined their watercourse international boundaries by a median line, left bank, right bank, etc. Stream gradient USGS, Stream Modeling website
8.
Flood
–
A flood is an overflow of water that submerges land which is usually dry. The European Union Floods Directive defines a flood as a covering by water of land not normally covered by water, in the sense of flowing water, the word may also be applied to the inflow of the tide. Floods can also occur in rivers when the flow exceeds the capacity of the river channel. Floods often cause damage to homes and businesses if they are in the flood plains of rivers. Some floods develop slowly, while others such as floods, can develop in just a few minutes. Additionally, floods can be local, impacting a neighborhood or community, or very large, the word flood comes from the Old English flod, a word common to Germanic languages. Deluge myths are stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths, surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience flooding during periods when precipitation exceeds evaporation. Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the worlds largest rivers. When overland flow occurs on tilled fields, it can result in a flood where sediments are picked up by run off. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, the cause may be localized convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. In one instance, a flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the rate increased from about 50 to 1,500 cubic feet per second in just one minute. Two larger floods occurred at the site within a week
9.
Los Angeles
–
Los Angeles, officially the City of Los Angeles and often known by its initials L. A. is the cultural, financial, and commercial center of Southern California. With a census-estimated 2015 population of 3,971,883, it is the second-most populous city in the United States, Los Angeles is also the seat of Los Angeles County, the most populated county in the United States. The citys inhabitants are referred to as Angelenos, historically home to the Chumash and Tongva, Los Angeles was claimed by Juan Rodríguez Cabrillo for Spain in 1542 along with the rest of what would become Alta California. The city was founded on September 4,1781, by Spanish governor Felipe de Neve. It became a part of Mexico in 1821 following the Mexican War of Independence, in 1848, at the end of the Mexican–American War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, thereby becoming part of the United States. Los Angeles was incorporated as a municipality on April 4,1850, the discovery of oil in the 1890s brought rapid growth to the city. The completion of the Los Angeles Aqueduct in 1913, delivering water from Eastern California, nicknamed the City of Angels, Los Angeles is known for its Mediterranean climate, ethnic diversity, and sprawling metropolis. Los Angeles also has an economy in culture, media, fashion, science, sports, technology, education, medicine. A global city, it has been ranked 6th in the Global Cities Index, the city is home to renowned institutions covering a broad range of professional and cultural fields, and is one of the most substantial economic engines within the United States. The Los Angeles combined statistical area has a gross metropolitan product of $831 billion, making it the third-largest in the world, after the Greater Tokyo and New York metropolitan areas. The city has hosted the Summer Olympic Games in 1932 and 1984 and is bidding to host the 2024 Summer Olympics and thus become the second city after London to have hosted the Games three times. The Los Angeles area also hosted the 1994 FIFA mens World Cup final match as well as the 1999 FIFA womens World Cup final match, the mens event was watched on television by over 700 million people worldwide. The Los Angeles coastal area was first settled by the Tongva, a Gabrielino settlement in the area was called iyáangẚ, meaning poison oak place. Gaspar de Portolà and Franciscan missionary Juan Crespí, reached the present site of Los Angeles on August 2,1769, in 1771, Franciscan friar Junípero Serra directed the building of the Mission San Gabriel Arcángel, the first mission in the area. The Queen of the Angels is an honorific of the Virgin Mary, two-thirds of the settlers were mestizo or mulatto with a mixture of African, indigenous and European ancestry. The settlement remained a small town for decades, but by 1820. Today, the pueblo is commemorated in the district of Los Angeles Pueblo Plaza and Olvera Street. New Spain achieved its independence from the Spanish Empire in 1821, during Mexican rule, Governor Pío Pico made Los Angeles Alta Californias regional capital
10.
Los Angeles flood of 1938
–
The Los Angeles flood of 1938 was responsible for inundating much of Los Angeles, Orange, and Riverside counties, California during February and March 1938. The flood was caused by a pair of Pacific storms that swept inland across the Los Angeles Basin, between 113 to 115 people were killed in what ultimately became one of the most catastrophic natural disasters in Southern California history. The flood caused the Santa Ana, Los Angeles, and San Gabriel Rivers to burst their banks, washing away roads, bridges, and buildings, the flooding event of 1938 is considered a 50-year flood. It resulted in $40 million of damages, and the Red Cross deemed it the fifth largest flood in history, in response to the floods, the U. S. Army Corps of Engineers began channelizing local streams and building more flood control dams. Dams built in the aftermath of the flood include Sepulveda Dam, Hansen Dam, Prado Dam, and Whittier Narrows Dam, which hydrologically connects the San Gabriel River to the Rio Hondo. Between February 27 and 28,1938, a storm from the Pacific Ocean moved inland into the Los Angeles Basin, the area received almost constant rain totaling 4.4 in from February 27-March 1. This caused minor flooding that affected only a few buildings in isolated canyons, fifteen hours later on March 1, at approximately 8,45 PM, a second storm hit the area, creating gale-force winds along the coast and pouring down even more rain. The storm brought rainfall totals to 10 in in the lowlands and upwards of 32 in in the mountains, when the storm ended on March 3, the resulting damage was horrific. Overall, the flood of 1938 destroyed 5,601 buildings, damaging a further 1,500, the floods carried large amounts of debris and sediment down from the mountains, burying roads and stopping traffic for many days. The general hospital of Los Angeles County was threatened by rising floodwaters, more than 20 structures were destroyed in the Arroyo Seco canyon, but there were no fatalities there. Damage was probably most severe along the Santa Ana River in San Bernardino, Riverside, without any flood control dams, the river swelled to over 317,000 cu ft/s, almost half the flow of the Mississippi River. The flooding was so intense that it transformed most of low-lying northwestern Riverside County, the town of Agua Mansa in Riverside County, with a population of over 200, was completely swept away. The cities of Anaheim and Santa Ana, further downstream in Orange County, were covered with up to 6 feet of water, the Los Angeles River reached a maximum flood stage of 130,000 cu ft/s. The Tujunga Wash reached its peak flow on March 3, with a flow of an estimated 50,000 cu ft/s. In the San Fernando Valley, the swept through many areas after escaping their normal channels of Tujunga Creek. Waters reached deep into the valley and flooded portions of Van Nuys and this extensive flooding brought about the building of Hansen Dam. The San Gabriel River reached a peak of 150,000 cu ft/s at the confluence of the East and West Forks, the water swept into the reservoir of the nearly completed San Gabriel Dam, filling it to capacity. Dam operators held releases to a maximum of 90,000 cu ft/s, as a results, large areas of the San Gabriel Valley were spared from flooding, although damage still occurred locally on smaller streams that drain out of the mountains
.JPG)
_pictogram.svg)
