131-429: San Gabriel River is the name of watercourses in two states: San Gabriel River (California) San Gabriel River bicycle path (California) San Gabriel River (Texas) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title San Gabriel River . If an internal link led you here, you may wish to change
262-524: A braided channel along its relatively wide canyon floor. It flows into the West Fork just below Hoot Owl Flats, a short distance from the larger river's mouth at San Gabriel Reservoir . The North Fork is the most heavily developed fork of the San Gabriel River, with many campgrounds and facilities along its course. The popular Crystal Lake Recreation Area in the upper North Fork includes
393-711: A combination of factors including the depletion of easily accessible gold deposits, harsh weather conditions, and the political instability at the time. The Welsh gold rush occurred in Wales , more so in the Dolgellau area of Gwynedd , during the 19th century. Gold deposits were discovered in Welsh mountains, with reports of gold being found in rivers Mawddach and Tryweryn . By the mid-19th century, commercial mining operations had begun. Wales' gold gained popularity for its quality and rarity, leading to its use in royal jewelry for
524-722: A critical source of income and livelihood, providing employment opportunities and economic support in regions with limited alternative options. Artisanal mining operations vary in scale, from individuals panning for gold in rivers and streams, to small groups working collectibely in informal mining camps, often referred to as ' galamsey ' in West Africa . Gold mining can create employment opportunities in mining operations and related sectors. Howevers, these jobs may be temporary. The sector's reliance on fluctuating global gold prices can lead to economic stability for communities dependent on mining. The discovery of significant gold deposits in
655-437: A gravel screening plant and sluice box floating in a temporary pond. The pond is excavated in the gravel bar and filled from the natural water table. "Pay" gravel is excavated from the front face of the pond and processed through the floating plant, with the gold trapped in the onboard sluice box and tailings stacked behind the plant, steadily filling in the back of the pond as the operation moves forward. This type of gold mining
786-471: A large scale to extract gold from extensive alluvial (loose sediment) deposits, such as those at Las Medulas . Mining was under the control of the state but the mines may have been leased to civilian contractors some time later. The gold served as the primary medium of exchange within the empire, and was an important motive in the Roman conquest of Britain by Claudius in the first century AD; although there
917-488: A low level, in order to provide room for stormwater and allow county workers to remove built-up sediment from the basin. The northern part of the reservoir, when dry, is also used as the San Gabriel Canyon OHV area. There is no public boating access to either San Gabriel Reservoir or the downstream Morris Reservoir, which is used mainly for water supply. From World War II until the 1990s, Morris Reservoir
1048-488: A lower grade. Tailings can contain lead, mercury, cadmium, and arsenic. These toxins can pose health risks for local communities. Arsenic is typically found in gold-containing ores, and gold processing may contaminate groundwater or the atmosphere. This pollution may persist for decades. Furthermore, mining operations use large quantities of water for processing ore and can result in the contamination of water sources with heavy metals, such as mercury and cyanide , used in
1179-472: A nearly straight line from east to west across the center of the San Gabriel Mountains . In the winter, the mountain regions are prone to landslides and destructive debris flows , which has required the construction of many debris basins to protect foothill communities such as Glendora and Monrovia , but these works have not always been effective during the biggest storms. During floods,
1310-521: A number of U.S. Forest Service and Los Angeles County firefighting facilities before flowing into San Gabriel Reservoir , where it joins the West Fork. The West Fork , 19 miles (31 km) long, originates at Red Box Saddle , a visitor center and frequently-used trailhead along the Angeles Crest Highway and about 2 miles (3.2 km) northwest of the summit of Mount Wilson . Beginning at an elevation of 4,666 feet (1,422 m),
1441-679: A popular attraction of the Angeles National Forest . The San Gabriel River basin drains a total of 689 square miles (1,780 km ) and is located between the watersheds of the Los Angeles River to the west, the Santa Ana River to the east, and the Mojave Desert to the north. The watershed is divided into three distinct sections. The northern third, located within the Angeles National Forest of
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#17327730196481572-502: A recreational fishery. About 60,000 rainbows are stocked each year between October and June. The West Fork also has the largest remaining population of arroyo chub , a fish endemic to coastal Southern California streams. Although the first recorded inhabitants of the San Gabriel River area arrived about 2,500 years ago, humans may have been present in Southern California as early as 12,000 years ago. Immediately prior to
1703-458: A rich lowland ecosystem on its broad floodplain, inundated multiple times each year by rain and snowmelt. The result of this overflow was a 47,000-acre (19,000 ha) network of riparian and wetland habitats, ranging from seasonally-flooded areas in the north to alkali meadows (called "cienegas" by the Spanish), forests of willows, oaks, and cottonwoods, and both fresh- and salt-water marshes in
1834-532: A significant part of the Los Angeles coastal plain, emptying into the Pacific Ocean between the cities of Long Beach and Seal Beach . The San Gabriel once ran across a vast alluvial flood plain, its channels shifting with winter floods and forming extensive wetlands along its perennial course, a relatively scarce source of fresh water in this arid region. The Tongva and their ancestors inhabited
1965-650: A steep, rugged canyon. It is joined from the east by the Fish Fork , which originates on the northwest slopes of Mount Baldy. Below the Fish Fork, the East Fork flows through "the Narrows", one of the deepest gorges in Southern California. From the floor of the canyon at 3,000 feet (910 m), Iron Mountain rises 8,007 feet (2,441 m) to the southeast, while Mount Hawkins, 8,850 feet (2,700 m), rises to
2096-670: A system of large land grants which became the many ranchos of the area. The decline of Native American populations made it easy for colonists to seize large areas of land formerly used by the indigenous people. During the Spanish-controlled period, and the Mexican-controlled period between 1821 and 1846, cattle ranching dominated the local economy. In the San Gabriel River watershed, the Rancho Azusa de Dalton and Rancho Azusa de Duarte lay, respectively, to
2227-747: A tributary of the Klondike River by George Carmack and his Indigenous companions, Skookum Jim Mason and Tagish Charlie . As prospectors arrived in Klondike, makeshift towns and settlements sprang up along the rivers, including Dawson City , which because the largest town in Yukon at the height of the gold rush. Prospectors employed various mining techniques to extract gold from the Klondike's streams and riverbeds, including placer mining, dredging, and hydraulic mining. The Carlin Trend of Nevada, U.S.,
2358-418: Is a cyanide extraction method, or gold cyanidation, introduced in the late 1800s. This a metallurgical technique used to extract gold from lower grade ores by converting gold into a water-soluble coordination complex. Finely ground rock is treated with a solution of sodium cyanide . The extract is absorbed onto carbon and then removed from the carbon with a solution of caustic soda and cyanide. Gold cyanide
2489-429: Is a method of extracting gold from alluvial deposits such as sand, gravel, and sediment. These are known as placer deposits which are typically found in riverbeds, stream beds, and floodplains. These deposits typically contain minerals that are resistant to weathering and eroision like gold , platinum , diamonds , and more. They are characterized by their relatively high concentration of valuable minerals compared to
2620-557: Is a mostly- urban waterway flowing 58 miles (93 km) southward through Los Angeles and Orange Counties , California, in the United States. It is the central of three major rivers draining the Greater Los Angeles Area , the others being the Los Angeles River and Santa Ana River . The river's watershed stretches from the rugged San Gabriel Mountains to the heavily-developed San Gabriel Valley and
2751-415: Is characterized by its low cost, as each rock is moved only once. It also has low environmental impact, as no stripping of vegetation or overburden is necessary, and all process water is fully recycled. Such operations are typical on New Zealand's South Island and in the Klondike region of Canada. Also called a cradle, a rocker box uses riffles located in a high-walled box to trap gold in a similar manner to
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#17327730196482882-555: Is diverted into the first of several spreading grounds that recharge the local San Gabriel Valley aquifer , an important source of local water supply. The usually-dry riverbed then continues in a southwesterly direction, passing the ruins of the 1907 Puente Largo or "Great Bridge" that once carried Pacific Electric interurban trains, and under Interstate 210 into the flood control basin behind Santa Fe Dam . There are 17 drop structures or grade controls along this roughly 2-mile (3.2 km) stretch of river bed, to prevent erosion down
3013-616: Is done by small-scale miners using suction dredges. These are small machines that float on the water and are usually operated by one or two people. A suction dredge consists of a sluice box supported by pontoons, attached to a suction hose which is controlled by a miner working beneath the water. This method is particularly popular in areas where gold is found at river bottoms or submerge deposits . Suction dredging can have environmental impacts, moreso on aquatic habitats and water quality. Regulations and best practices are often in place to minimize these impacts. State dredging permits in many of
3144-436: Is essentially a man made channel with riffles set in the bottom. The riffles are designed to create dead zones in the current to allow gold to drop out of suspension. The box is placed in the stream to channel water flow. Gold-bearing material is placed at the top of the box. The material is carried by the current through the volt where gold and other dense material settles out behind the riffles. Less dense material flows out of
3275-868: Is estimated that the total gold production in Karnataka to date is 1000 tons. The mining of the Hungarian deposit (present-day Slovakia) primarily around Kremnica was the largest of the Medieval period in Europe. In South America, gold mining in the Andes dates back to thousands of years, with the Inca empire employing extensive gold mining operations in regions such as present-day Peru and Ecuador . They used stone tools and simple mining techniques to extract gold from rivers, streams, and surface deposits. During
3406-518: Is one of the largest natural streams in Southern California, but its discharge varies widely from year to year. Between 1895 and 1957 the mean unimpaired runoff at Azusa was estimated at 114,000 acre-feet (141,000,000 m ), with a range from 9,600 to 410,000 acre-feet (11,800,000 to 505,700,000 m ). Historically, the San Gabriel River reached its highest flows in the winter and spring, with runoff dropping significantly after early June before rising again with November or December storms. Today,
3537-698: Is only one known Roman gold mine at Dolaucothi in west Wales. Gold was a prime motivation for the campaign in Dacia when the Romans invaded Transylvania in what is now modern Romania in the second century AD. The legions were led by the emperor Trajan, and their exploits are shown on Trajan's Column in Rome and the several reproductions of the column elsewhere (such as the Victoria and Albert Museum in London ). Under
3668-966: Is produced by major corporations, there are an estimated 10 to 15 million small-scale artisanal gold miners worldwide. Around 4.5 million of them are women, and an estimated 600,000 children work in illegal artisanal gold mines. Artisanal miners use rudimentary methods to extract and process gold. Many of these people are mining to escape extreme poverty , unemployment and landlessness . In Ghana, galamsey miners are estimated to number 20,000 to 50,000. In neighboring francophone countries, such workers are called orpailleurs . In Brazil, Venezuela, Suriname, and French Guiana, workers are called garimpeiros . These workers are not required to claim responsibility for their social and environmental impacts. Miners risk government persecution, mine shaft collapses, and toxic poisoning from unsafe chemicals used in processing, such as mercury. For example, in Ghana during 2009,
3799-633: Is then converted to relatively pure gold through gold parting . There are many environmental hazards associated with this extraction method, largely due to the high toxicity of the cyanide compounds. Furthermore, there are potentials for accidental spills or leaks to cause harm to aquatic ecosystems and human health. For example, in 2000, the Baia Mare cyanide spill in northern Romania released approximately 100,000 cubic metres (3,500,000 cu ft) of waste water contaminated with heavy metal sludge and up to 120 long tons (122 t) of cyanide into
3930-532: Is unknown, but some of the oldest known gold artifacts were found in the Varna Necropolis in Bulgaria . The graves of the necropolis were built between 4700 and 4200 BC, indicating that gold mining could be at least 6,724 years old. During a series of excavations carried out between 1878 and 1992, several graves were found with more than 6kg of gold. A group of German and Georgian archaeologists claims
4061-635: The British royal family . During the 19th century, numerous gold rushes in remote regions around the globe caused large migrations of miners, such as the California Gold Rush of 1849. This is one of the most famous gold rushes in history. The discovery of gold at Sutter's Mill in California sparked a massive migration of people from around the world to California in search of gold. The rush significantly accelerated westward expansion in
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4192-722: The Bronze Age , sites in the Eastern Desert became a great source of gold-mining for nomadic Nubians, who used "two-hand-mallets" and "grinding ore extraction ." By the Old Kingdom , the oval mallet was introduced for mining. By the Middle Kingdom , stone mortars to process ores and a new gold-washing technique were introduced. During the New Kingdom , Nubian mining expanded under Egyptian occupation with
4323-578: The Dompoase mine collapse killed 18 workers. It was the worst mining disaster in Ghanaian history. Children in these mines suffer extremely harsh working conditions and various hazards such as collapsing tunnels, explosions, and chemical exposure. Children may be especially vulnerable to these hazards and many suffer from serious respiratory conditions, hearing, and vision problems. Gold mining by large multi-national corporations produces about 80% of
4454-690: The Kolar gold fields was mined to a depth of 50 metres (160 ft) during the Gupta period in the fifth century AD. During the Chola period in the 9th and 10th century AD, the scale of the operation grew. The metal continued to be mined by the eleventh century kings of South India, the Vijayanagara Empire from 1336 to 1560, and later by Tipu Sultan , the king of Mysore state and the British. It
4585-551: The Metro C Line , then crossing under SR 91 at Bellflower . The San Gabriel River Bike Trail parallels the river starting at Whittier Narrows for 28 miles (45 km) to the Pacific Ocean at Seal Beach. From Cerritos the river flows south-southeast until reaching its confluence with Coyote Creek , the largest tributary of the lower river, which drains much of northwest Orange County. A short distance below Coyote Creek,
4716-462: The Sakdrisi site in southern Georgia , dating to the 3rd or 4th millennium BC, may be the world's oldest known gold mine. Gold has been prized by humans since prehistoric times. Archaeological evidence suggests that humans were mining gold as far back as 4000 BCE, with some the earliest known gold artifacts dating back to ancient Mesopotamia . Particularly in the region of present-day Iraq, gold
4847-673: The San Andreas Fault (the boundary between the North American Plate and Pacific Plate ) and its subsidiary fault and fracture zones. The San Gabriel Mountains are a fault block mountain range, essentially a massive chunk of bedrock dislocated from the North American Plate and lifted up by movement along the San Andreas. The rock is mostly of Mesozoic origin (65–245 million years old), but
4978-600: The San Gabriel Valley , and the southern third, the coastal plain of the Los Angeles Basin , are separated by the Puente Hills and Montebello Hills . With the exception of some recreation areas and lands set aside for flood control, the valleys are almost entirely urbanized. Approximately 2 million people live in the watershed, divided among 35 incorporated cities. Rainfall is slightly higher in
5109-602: The Santa Ana River . Once every few decades, a particularly intense storm would cause the rivers to burst their banks simultaneously, inundating the coastal plain in a continuous sheet of floodwater. The historical floodplain encompassed much of the San Gabriel Valley and a huge expanse of the Los Angeles Basin stretching from present-day Whittier to Seal Beach. The thick sediments of the lowland also trap an extensive local aquifer system. Historically,
5240-517: The Tisza River. Historically, mercury was used extensively in placer gold mining in order to form mercury-gold amalgam with smaller gold particles, and thereby increase the gold recovery rates. First, the gold ore is crushed and ground to a fine powder to expose the gold particles for amalgamation. Then, this finely ground ore is mixed with liquid mercury to amalgamate it. Mercury forms an amalgam, an alloy, with gold particles to allow for
5371-683: The West Fork of the San Gabriel. Its furthest tributary, the Prairie Fork, originates at 9,648-foot (2,941 m) Pine Mountain in the Sheep Mountain Wilderness to the southwest of Wrightwood . Draining a high, remote, subalpine valley characterized by extensive meadows, it flows west to join with Vincent Gulch, below which the stream is officially known as the East Fork. Here it turns abruptly south, flowing through
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5502-489: The last ice age when the regional climate was much wetter. The montane forests are home to large mammals such as deer and black bears. Due to conservation policies put in place by the 19th century, the upper San Gabriel watershed was never subjected to heavy logging. Also in the San Gabriel River watershed is the 17,000-acre (6,900 ha) San Dimas Experimental Forest , a UNESCO Biosphere Reserve where forest hydrology has been continually studied since 1933. Lower down in
5633-413: The 27,800-acre-foot (34,300,000 m ) Morris Reservoir . A small hydroelectric plant in the city of Azusa is supplied with water from a diversion of the San Gabriel River, located directly below San Gabriel Dam. The reservoir water levels fluctuate widely at the upper San Gabriel Reservoir, which serves mainly for flood control and sediment control. During the dry season the reservoir is often kept at
5764-574: The Amazon rainforest, Indigenous peoples have been killed and had their rightfully owned land stolen from them. As a consequence of this, some have left the rainforest to move to cities which further puts them at risk to disease, homelessness, and poverty. Artisanal gold mining is widespread across Africa , occurring in numerous countries including Ghana , Mali , Burkina Faso , Tanzania , Zimbabwe , and many others. For many individuals and communities in rural Africa, artisanal gold mining represents
5895-563: The Devore campground, above Cogswell Reservoir. Below Cogswell Dam, the river is paralleled by Forest Route 2N25, a one-lane paved road open only to non-motorized traffic (except for maintenance and emergency services). The river flows east through a twisting canyon, forming the southern boundary of the San Gabriel Wilderness . It receives the tributaries of Chileno Canyon, Little Mermaids Canyon, and Big Mermaids Canyon from
6026-572: The East Fork and West Fork, the San Gabriel River flows through the deep San Gabriel Canyon, the only major break in the southern part of the San Gabriel Mountains. Although this stretch of the river was once free-flowing, today is it impounded by major reservoirs for water supply and flood control. San Gabriel Dam , a 325-foot (99 m) high rockfill dam, forms the 44,183-acre-foot (54,499,000 m ) San Gabriel Reservoir . The concrete gravity Morris Dam , just downstream, creates
6157-571: The East Fork, grew to include "a boarding house, two or three stores, blacksmith shop, butcher shop, etc." A flood in November 1859 destroyed the settlement, but four months later it was re-established as the town of Eldoradoville , near the junction of the East Fork and Cattle Canyon. The period from 1859 to 1862 was the most prosperous of the San Gabriel gold rush; Wells Fargo stages alone shipped some $ 15,000 ($ 457,800 in 2023 dollars) worth of gold per month out of Los Angeles County, most of it from
6288-918: The Eastern Roman Empire Emperor Justinian's rule, gold was mined in the Balkans, Anatolia, Armenia, Egypt, and Nubia. In the area of the Kolar Gold Fields in Bangarpet Taluk , Kolar district of Karnataka state, India; gold was first mined prior to the 2nd and 3rd century AD by digging small pits. Golden objects found in Harappa and Mohenjo-daro have been traced to Kolar through the analysis of impurities – the impurities include 11% silver concentration, found only in KGF ore. The Champion reef at
6419-469: The Highlands during the 16th and 17th century. Gold deposits were discovered in rivers and streams, leading to a surge in prospecting and mining activity. The Scottish Crown took an interest in gold discoveries, in hopes of aiding the kingdom's economy and revenue. King James IV of Scotland established a royal mint to produce gold coins from Scottish gold. The Scottish gold rush eventually waned due to
6550-954: The Middle Ages, Europe experience several gold rushes. Most notably in regions like Transylvania, Scotland, and Wales. These rushes were often small-scale and localised compared to later rushes in history. The Transylvania gold rush took place in the Kingdom of Hungary (present-day Romania ), primarily in the region of Transylvania during the medieval period. Transylvania was known for its rich mineral resources including gold, silver, and other metals. Miners in Transylvania used both surface and underground mining techniques to extract gold from alluvial deposits and veins. These methods include panning, sluicing, and rudimentary shaft mining. The Scottish gold rush occurred in Scotland, primarily in
6681-551: The Narrows, the river continues flowing south through a somewhat-more-open valley, receiving several tributaries including Devil Gulch and Allison Gulch, before reaching Heaton Flat, a popular trailhead and the end of the East Fork Road , which parallels the lower section of the river. The river receives Cattle Canyon, its biggest tributary, and then turns sharply west, flowing past the Camp Williams Resort and
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#17327730196486812-400: The Pacific Ocean to spawn, and it was known as one of the "best steelhead fishing rivers in the state". Irrigation development that dried up the river, and later damming and channelization for flood control, have contributed to the near extinction of steelhead in the San Gabriel basin. Since the 19th century rainbow trout have been planted in the upper forks of the San Gabriel River to provide
6943-543: The San Gabriel Canyon long before California became a U.S. state, gold was first confirmed in the upper San Gabriel River around April 1855, by a party of prospectors who had entered the mountains via Cajon Pass . The Los Angeles Star soon reported of their findings: There has been some excitement this past week about the new gold diggings on the headwaters of the San Gabriel. We have met several persons who have been prospecting and although they found gold of
7074-445: The San Gabriel Mountains, is steep and mountainous; it receives the most precipitation of any part of the basin – 33 inches (840 mm) per year – and as a result is the source of nearly all the natural runoff. Elevations reach up to 10,064 feet (3,068 m) at Mount San Antonio (Mount Baldy), the highest point of the range. During the winter, many elevations above 6,000 feet (1,800 m) are covered in snow. The middle third,
7205-454: The San Gabriel River basin for thousands of years at villages like Puvunga , relying on the abundant fish and game in riparian habitats. The river is named for the nearby Mission San Gabriel Arcángel , established in 1771 during the Spanish colonization of California . Its water was heavily used for irrigation and ranching by Spanish, Mexican, and American settlers before urbanization began in
7336-438: The San Gabriel Valley than the coastal plain due to its proximity to the mountains; however, the climate as a whole is very arid, with only moderate precipitation in winter and nearly none in summer. The lower watershed consists primarily of alluvial plains that once experienced seasonal flooding from the San Gabriel River, creating vast swamps and wetlands. Today, very little of this original environment remains. The San Gabriel
7467-403: The San Gabriel Valley, resulting in a severe decline of the water table as farmers drilled hundreds of wells. The San Gabriel Valley aquifer is now an important source of domestic and industrial water, and groundwater recharge operations are conducted using both local runoff from the San Gabriel River, and water imported through Los Angeles's aqueduct system. The San Gabriel River once supported
7598-678: The San Gabriel diggings. John Robb, who ran a saloon in Eldoradoville, claimed he "made more money by running the sawdust from the floor of the Union Saloon through his sluice box than he was able to make from real mining, so prodigal and careless of their pokes were the miners and gamblers of those days." Gold mining Gold mining is the extraction of gold by mining . Historically, mining gold from alluvial deposits used manual separation processes, such as gold panning . The expansion of gold mining to ores that are not on
7729-413: The San Gabriels in later years, such as at the 1896 Big Horn Mine at Mount Baden-Powell , and the 1913 Allison Mine on Iron Mountain high above the East Fork, where several tunnels of up to 1,000 feet (300 m) in length remain. Settlements of considerable size were established in very rough country along the upper San Gabriel River. Prospect Bar, located 4 miles (6.4 km) up the narrow canyon of
7860-427: The Spanish. Disease severely reduced the native populations, and by the beginning of the 19th century, most of the surviving Gabrieliño had entered the mission system. In 1830, nine years after California had become a part of Mexico , the indigenous population had fallen to about a quarter of what it had been before Spanish colonization. In order to attract settlers to the region, Spain and later Mexico established
7991-430: The Tongva described them as a peaceful people. Anthropologists believe the Tongva may have been some of the more advanced native inhabitants of California, establishing currency and complex trade systems with neighboring tribes, cultivating trees and plants for food, and having a formal government structure. Indian Agent B.D. Wilson wrote in 1852 the Tongva knew "how to meet the environmental challenge without destroying
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#17327730196488122-410: The United States and had profound effects on the region's economy and society. The gold rushes began in 1851 when Edward Hargraves , a prospector, discovered gold near Bathhurst , New South Wales . The most well known gold rush in Australia was the Victorian Gold Rush . Thousands of people, known as 'diggers', came from around the world to Australia in search of gold, which ultimately contributed to
8253-484: The United States gold dredging areas specify a seasonal time period and area closures to avoid conflicts between dredgers and the spawning time of fish populations. Some US states, such as Montana, require an extensive permitting procedure, including permits. Some large suction dredges [100 horsepower (75 kW) & 250 mm (10 in)] are used in commercial production throughout the world. Small suction dredges are much more efficient at extracting smaller gold than
8384-403: The West Fork flows at a much lower elevation than the East Fork and is the smaller of the two rivers in terms of water volume. The West Fork flows east in a fairly straight course for its entire length. From its headwater, the river quickly descends to the Cogswell Reservoir , where Devils Canyon Creek joins from the north. The Gabrielino Trail parallels the river from Red Box Saddle as far as
8515-405: The aquifer was quite pressurized and close to the surface; natural artesian wells existed in many places. At the southern end of the San Gabriel Valley, groundwater rose to the surface due to the damming effect of bedrock at the Whittier Narrows and formed a perennial stream that ran across the coastal plain to the Pacific. In the 19th century, irrigated agriculture was developed on a large scale in
8646-409: The area although people from some other groups, such as the Chumash, were also present at the San Gabriel mission. Native Americans fleeing the mission system took refuge in the upper canyons of the San Gabriel River where a significant resistance movement persisted for many years. This culminated in the San Gabriel mission uprising in 1785, led by Tongva medicine woman Toypurina , ultimately crushed by
8777-467: The arrival of Spanish explorers in the region, the native population is estimated at 5,000–10,000. Mount San Antonio provided a visual reference for the boundary of the Tongva (Gabrielino) people in the west and the Yuhaviatam people to the east. Most of the San Gabriel River lay in traditional Tongva territory, although the Chumash (who inhabited areas further west) also used the area. Tongva villages such as Puvunga were located on high ground above
8908-405: The availability of space in the downstream channels. Below the Whittier Narrows Dam, the river flows south-southwest across the coastal plain, roughly defining the border of Los Angeles County and Orange County . It flows through Whittier and Pico Rivera and under the Interstate 5 to Downey , where the river becomes a concrete channel. It turns due south, crossing under Interstate 105 and
9039-446: The best quality, differ very much as regards to the richness of the mine. The Crab Hollow diggings are now considered the best and will pay from two to five cents to the pan. The river remained quiet for a number of years, as drought conditions reduced streamflow and made placer mining difficult. The winter of 1858-59 was a wet one, and soon hundreds of gold seekers from both Los Angeles County and Kern County further north descended on
9170-580: The box as tailings . Larger commercial placer mining operations employ screening plants, or trommels , to remove the larger alluvial materials such as boulders and gravel, before concentrating the remainder in a sluice box or jig plant. After the gold is sorted through trommels, it is then placed through regular sluice boxes for further sorting. These operations typically include diesel powered, earth moving equipment including excavators, bulldozers, wheel loaders , and rock trucks. Although this method has largely been replaced by modern methods, some dredging
9301-436: The coastal plain, had the highest population density. Villages in the San Gabriel Valley included Alyeupkigna , Amuscopopiabit, Awingna , Comicranga, Cucamonga , Guichi, Houtgna , Isanthcogna , Juyubit , Perrooksnga, Sibagna , and Toviseanga . The village of Sejat was located at the Whittier Narrows. Puvugna was situated around present-day Long Beach , near the river's mouth. The first explorers to make contact with
9432-526: The coastal plain. California became a U.S. state in 1850, two years after the Mexican–American War . One of the decisive battles of the war was fought on January 8, 1847 on the San Gabriel River, which was the last line of defense for Mexican Californio forces led by Mexican Governor-General José Flores , tasked with defending the pueblo of Los Angeles. American forces, led by General Stephen W. Kearney under Commodore Robert F. Stockton , crossed
9563-540: The crest of the range between Mount Islip and Mount Hawkins, more than 7,000 feet (2,100 m) above sea level. Cedar Creek flows south from Windy Gap , 7,588 feet (2,313 m), to join with Soldier Creek, which continues south past Falling Springs to join with Coldbrook Creek, forming the North Fork. The North Fork continues south for 4.5 miles (7.2 km) past Valley of the Moon Plantation, forming
9694-512: The deepest layers are up to 4 billion years old. However, the uplift of the present mountain range did not start until about 6 million years ago. The mountains are still rising as much as 2 inches (51 mm) per year due to tectonic action along the San Andreas Fault. The Puente and Montebello hills are even younger, no more than 1.8 million years old. As the hills formed, the San Gabriel River maintained its original course, cutting
9825-681: The development of the floodplain, the river channels down the alluvial slope were poorly-defined at best and frequently changed course with winter storms, leaping back and forth between several different ocean outlets. In some years it joined with the Rio Hondo , which flows parallel to the San Gabriel and also passes through the Whittier Narrows , and flowed into the Los Angeles River; in others it would swing south toward either Alamitos Bay or Anaheim Bay , or even east towards
9956-520: The early 1900s, eventually transforming much of the watershed into industrial and suburban areas of greater Los Angeles. Severe floods in 1914, 1934, and 1938 spurred Los Angeles County, and later the federal government, to build a system of dams and debris basins and to channelize much of the lower San Gabriel River with riprap or concrete banks. There is also an extensive system of spreading grounds and other works to capture stormwater runoff and conserve it for urban use. Approximately one-third of
10087-494: The east and west of the San Gabriel Canyon mouth. Rancho San Francisquito , Rancho Potrero Grande , Rancho Potrero de Felipe Lugo , Rancho La Puente , and Rancho La Merced were located further south in the San Gabriel Valley. Rancho Paso de Bartolo was situated in the Whittier Narrows area, and Rancho Santa Gertrudes , Rancho Los Coyotes , Rancho Los Cerritos and Rancho Los Alamitos occupied various areas of
10218-549: The east, before passing under SR 60 . The river then enters the Whittier Narrows , the natural water gap between the Puente and Montebello Hills that forms the southern entrance to the San Gabriel Valley. Here it is impounded by the Whittier Narrows Dam , which serves primarily for flood control. The Rio Hondo also flows through the Whittier Narrows, to the west of the San Gabriel. The Rio Hondo drains most of
10349-432: The efficient capture of gold from the ore. The gold is concentrated by boiling away the mercury from the amalgam . This process is called retorting. This is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour. Large-scale use of mercury stopped in the 1960s. However, mercury is still used in artisanal and small-scale gold mining (ASGM). While most gold
10480-418: The environment." The abundant water available in the San Gabriel River basin, a rarity in arid Southern California, was noted by early Spanish explorers and made it an attractive place for Europeans to settle later on. Juan Rodriguez Cabrillo sailed past the mouth of the San Gabriel River in 1542; although he did not land here, he did make contact with the native Tongva, who rowed out in their canoes to greet
10611-721: The expedition. The first Spanish party to actually cross the river was the Portolà expedition , led in 1769 by Captain Gaspar de Portolà . Juan Crespí , a missionary traveling with the expedition, described their first impression of the San Gabriel River: We then descended to a broad and spacious plain ... After traveling for an hour through the valley we came to an arroyo of water which flows among many green marshes, their banks covered with willows and grapes, blackberries, and innumerable Castilian rosebushes ... It runs along
10742-762: The extraction process. This pollution can have detrimental effects on aquatic ecosystems and human health. Soil degradation has also been found to be impacted by gold mining. Mining activities can disturb soil structure, leading to erosion, sedimentation of waterways, and loss of fertile land for agriculture or vegetation regrowth. More evidently, dust and emissions from mining machiner and processing facilities can contribute to air pollution, impacting air quality and potentially causings respiratory problems for nearby communities. Large-scale gold mining projects may require land acquisition and resettlement of local communities, leading to displacement, loss of livelihoods, and disruption of traditional ways of life. In addition to
10873-418: The flow of the San Gabriel River has been dried up in places by dams, diversions, and groundwater recharge operations, and increased in other sections by wastewater run-off. The East Fork , 17 miles (27 km) long, is the largest headwater of the San Gabriel River; the U.S. Geological Survey considers it part of the main stem . However, it is colloquially known as the "East Fork" to distinguish it from
11004-472: The foot of the mountains, and can be easily used to irrigate the large area of good land ... The valley ... is surrounded by ranges of hills. The one to the north is very high and dark and has many corrugations, and seems to run farther to the west. The expedition had to build a bridge across the river because the channel was too swampy and muddy, making it difficult to move their horses and supplies. The area came to be known as "la puente" (the bridge), from which
11135-510: The foothill zones, chaparral and brush dominate. The Puente Hills , which bisect the lower San Gabriel watershed, contain some sensitive plant communities such as coastal sage scrub and walnut forests. Wildfires are a natural part of plant communities in the San Gabriel River watershed. After the flood of 1938, an intense program of wildfire suppression began, since burned areas tend to erode quickly during storms, causing landslides and mudflows down tributary canyons. Like many other areas of
11266-694: The gold supply. Most gold is mined in developing nations. Large mining companies play a key role in globalisation of the economy by linking rich and poor companies. Newmont and Barrick Gold are the largest gold mining companies in the world, but there are many smaller corporations in the industry. Local communities are frequently vulnerable to environmental degradation caused by large mining companies and may lack government protection or industry regulation. For example, thousands of people around Lega Dembi mine are exposed to mercury, arsenic, and other toxins resulting in widespread health problems and birth defects. Vulnerable communities may also lose their land to
11397-567: The growth of cities like Melbourne and Sydney . The discovery of gold in the Witwatersrand led to the Second Boer War and ultimately the founding of South Africa. This transformed the region into one of the wealthiest gold-producing areas in the world. This rush played a crucial role in the development of South Africa's economy and lead to the establishment of Johannesburg, known as the 'city of gold'. Gold-bearing reefs in
11528-765: The heat is unbearable for humans, and air conditioning is required for the safety of the workers. The first such mine to receive air conditioning was Robinson Deep , at that time the deepest mine in the world for any mineral. Gold is also produced by mining in which it is not the principal product. Large copper mines, such as the Bingham Canyon mine in Utah, often recover considerable amounts of gold and other metals along with copper. Sand and gravel pits, like those in Denver (Colorado), may recover small amounts of gold in their wash operations. The largest producing gold mine in
11659-595: The invention of the grinding mill . Additionally, gold was associated with the sun god Ra and was believed to be eternal and indestructible, symbolising the pharoah's divine power and afterlife. Gold has also been found in the tombs of Tutankhamun and other pharoahs. During the Bronze Age, gold objects were also plentiful; especially in Ireland and Spain. Romans employed slave labour and used hydraulic mining methods, such as hushing and ground sluicing on
11790-656: The largest Tongva villages, Asuksangna (meaning "place of the grandmothers") was located at the mouth of the San Gabriel Canyon. The West Fork of the San Gabriel River Canyon formed part of a trade route that crossed the San Gabriel Mountains, enabling the Tongva to trade with the Serrano people in the Mojave Desert to the north. Many other villages were located near the San Gabriel River. The San Gabriel Valley, with its fertile soils and higher rainfall than
11921-545: The largest wildfire in Los Angeles County's history, was mostly concentrated west of the San Gabriel watershed, but did burn much of the upper West Fork. With urban development expanding toward mountain areas, the threat of property damage continues to increase. The San Gabriel River historically supported large populations of native fish, including the largest runs of steelhead in Southern California. Steelhead once migrated over 60 miles (97 km) upriver from
12052-450: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=San_Gabriel_River&oldid=933107618 " Categories : Disambiguation pages Place name disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages San Gabriel River (California) The San Gabriel River
12183-461: The lowest ever recorded for tropical forests, with there being little to no tree regeneration at abandoned mining camps, even after several years. The Amazon rainforest is at risk for 'savannization', which is the gradual transformation of a tropical rainforest into a savannah. This would ultimately lead to a collapse of biodiversity, ecosystems, and climate. Gold mining produces more waste than mining of other minerals, because it can be mined at
12314-663: The mine. Some large companies have attempted to build local legitimacy through corporate responsibility initiatives and local development. Gold mining can significantly alter the natural environment. Gold mining activities in tropical forests are increasingly causing deforestation along rivers and in remote areas rich in biodiversity. Mining has increased rainforest loss up to 70km beyond lease boundaries, causing nearly 11,670 km of deforestation between 2005 to 2015. Up to 9% of gold mining occurs outside of these regulated lease boundaries. Other gold mining impacts, particularly in aquatic systems with residual cyanide or mercury (used in
12445-622: The mission was soon attached to the river as well as the San Gabriel Mountains, which had been previously called the Sierra Madre by the Spanish. The original site suffered chronic flooding and was moved to its present site in San Gabriel , 5 miles (8.0 km) northwest, in 1775. The mission eventually controlled 1,500,000 acres (610,000 ha) of land extending from the foot of the mountains as far as present-day San Pedro . Under
12576-470: The modern-day city of La Puente takes its name. Following the Portolà expedition, Spain claimed California as part of its empire, and the San Gabriel River was referred to as "Río San Miguel Arcángel". Mission San Gabriel Arcángel , the fourth in a chain of missions along the California coast, was founded in 1771 by Junípero Serra , along the San Gabriel River near present-day Montebello . The name of
12707-594: The mountains, most of the streams are locked in artificial channels, and the vast majority of the original wetlands have been lost to urban development. Less than 2,500 acres (1,000 ha) of wetlands remain in the San Gabriel River watershed, with the greatest decline in the coastal floodplain zone. Most remaining wetland habitats are either immediately adjacent to the river, or within the Whittier Narrows and other flood control basins, providing habitat to birds and small mammals. In addition, riparian and wetland restoration projects have been completed or are in progress along
12838-530: The mouth of San Gabriel Canyon. This has combined with smaller alluvial fans from other drainages along the front range of the San Gabriels to form the flat valley floor. In the San Gabriel Valley, riverine alluvium deposits can be up to 10,000 feet (3,000 m) deep. On the coastal plain, San Gabriel River sediments are interbedded with those from the nearby Los Angeles River as well as marine sediments left behind from ancient sea level changes. Prior to
12969-744: The neighbouring Free State province were found shortly thereafter, driving significant development in the region with the establishment of the Free State goldfields . Also known as the Yukon Gold Rush , brought prospectors from around the world to the Klondike region of the Yukon territory in Canada . The Klondike Gold Rush began in 1896, when gold was discovered in Bonanza Creek ,
13100-423: The north, and then the much larger Bear Creek, which originates at Islip Saddle near the 8,250-foot (2,510 m) summit of Mount Islip . Less than a mile (1.6 km) below Bear Creek, it is joined by the North Fork before flowing into San Gabriel Reservoir , where it joins with the East Fork. The North Fork is the shortest and steepest of the three major forks. It begins as a series of streams falling off
13231-492: The northwest. The Iron Fork tributary joins from the west roughly in the middle of the Narrows. Near the lower end of the Narrows, the river passes under the Bridge to Nowhere , a 120-foot (37 m)-high arch bridge that was abandoned after the huge flood of 1938 washed out a highway under construction along the East Fork. The bridge remains today as a popular destination for hikers and bungee jumpers . After emerging from
13362-413: The old bucket line . This has improved the chances of finding gold. Smaller dredges with 50-to-100-millimetre (2 to 4 in) suction tubes are used to sample areas behind boulders and along potential pay streaks, until "colour" (gold) appears. Other larger scale dredging operations take place on exposed river gravel bars at seasonal low water. These operations typically use a land based excavator to feed
13493-413: The only natural lake in the San Gabriel Mountains . The North Fork valley provides the route for Highway 39 , which until 1978 provided automobile access from San Gabriel Canyon Road to the Angeles Crest Highway . Since then, the upper part of the road north of Crystal Lake has been closed due to chronic landslides and erosion. As of 2016, there are no plans to reopen the road. Below the confluence of
13624-473: The policy of reducción , the purpose being to "reduce or consolidate the Indians from the countryside into one central community", the Spanish incentivized Native Americans to joining the mission system first via gifts, but also often by force. Native people worked on farms and ranches of the mission lands, and were converted to Christianity. The Spanish name "Gabrieliño" generally refers to the Tongva people of
13755-688: The possible respiratory problems that could be acquired, individuals may be exposed to hazardous chemicals used in gold extraction such as mercury and cyanide. These chemicals pose risks to gold miners, communities, and wildlife; resulting in further medical problems involving neurological disorders and waterborne diseases . Gold mining in some regions has been associated with conflicts over land rights, labour rights violations, and exploitation of vulnerable populations, including Indigenous peoples and artisanal miners. Mining activities can damage or destroy cultural heritage sites, artifacts, and sacred areas; further impacting cultural identities and heritages. In
13886-496: The reach of winter floods. A typical village consisted of large, circular thatched huts known as "kich" or "kish", each home to multiple families. During summer, the villagers would travel up the San Gabriel Canyon into the mountains to gather food and other resources needed to pass the winter. The San Gabriel River itself also provided sustenance to Native Americans with its steelhead trout and game animals attracted by this rare permanent water source. The abundant plant life around
14017-407: The recovery of gold from ore), can be highly toxic to people and wildlife even at relatively low concentrations. Illegal gold mining exacerbates the ecological vulnerability of the remaining forest ultimately leading to permanent forest loss. Gold mining clears native forests for mineral extraction, but also indirectly facilitates access to more land and further clearing. Rainforest recovery rates are
14148-409: The river and its marshes, especially tule , were used to build dwellings and canoes. The Tongva often set brush fires to clear out old growth, improving forage for game animals. They also made oceangoing canoes (ti'at) using wooden planks held together with asphaltum or tar from local oil seeps . At least 26 Tongva villages were located along the San Gabriel River, and another 18 close by. One of
14279-694: The river bed reverts from concrete to earth. It passes under Interstate 405 and SR 22 , past Leisure World and Joint Forces Training Base - Los Alamitos (Los Alamitos Army Airfield), and under the Pacific Coast Highway . It empties into the Pacific Ocean between Alamitos Bay and Anaheim Bay (to the south), on the boundary of Long Beach in Los Angeles County, and Seal Beach in Orange County. The San Gabriel River, its canyons, and its floodplain are relatively young in geological terms, and owe their existence to tectonic forces along
14410-469: The river transports large volumes of sediment from the mountains into the San Gabriel Valley, ranging from fine sands, gravels, clays, and silt to car-sized boulders. Starting in the Pliocene , about 5 million years ago, the Los Angeles Basin experienced considerable tectonic subsidence; at the same time, the San Gabriel River was depositing a huge alluvial fan , essentially an inland delta, radiating from
14541-676: The river under heavy fire, but were able to force the Californios from their defensive position in under ninety minutes. After taking control of the river, the Americans were able to take Los Angeles on January 10, and the Mexicans surrendered California three days later. This campaign is now remembered as the Battle of Rio San Gabriel . Although it was rumored for many years that Native Americans and Spanish explorers had discovered gold in
14672-477: The river's east bank almost all the way to its mouth in Seal Beach . Throughout the San Gabriel Valley, the river flows mainly in an earth-bottomed channel between artificial concrete or riprap banks. Shortly below Interstate 10 at El Monte , the river is joined from the east by Walnut Creek , which restores a small perennial flow. Below this confluence it curves west and receives San Jose Creek , also from
14803-425: The river. By May 1859, claims were staked along 40 miles (64 km) of the San Gabriel Canyon. In the early days, access to the diggings proved difficult, as the rocky San Gabriel River bed was the only way into the rugged mountains. In July 1859, stagecoach service was established to bring in miners and their supplies. Between 1855 and 1902, an estimated $ 5,000,000 ($ 153 million in 2023 dollars) worth of gold
14934-461: The river. The San Gabriel River Wetland Restoration Development intends to construct by 2018 an artificial wetland and bioswale system near El Monte which will provide a recreation area and wildlife habitat and buffer against pollution. Above elevations of 7,000 feet (2,100 m), the San Gabriel Mountains support some pine and fir forests, remnants or relicts of a huge evergreen (coniferous) forest that once covered Southern California during
15065-549: The sluice box. A rocker box uses less water than a sluice box and is well suited for areas where water is limited. A rocking motion provides the water movement needed for the gravity separation of gold in placer material. Rocker boxes gained popularity during the California Gold Rush in the 19th century and remain in use today. Although simple and inexpensive, it is not efficient as the previously discussed mining techniques . The dominant method for refining gold
15196-409: The south. At its mouth, the river emptied into a broad estuary surrounded by thousands of acres of permanent marsh and swamp land, the result of a band of bedrock running parallel to the coast, forcing groundwater to the surface. In mountain areas, the San Gabriel River channel is often too narrow to support significant vegetation, as winter floods tend to scour the channel down to bare rock. Below
15327-630: The surface has led to more complex extraction processes such as pit mining and gold cyanidation . In the 20th and 21st centuries, most volume of mining was done by large corporations. However, the value of gold has led to millions of small, artisanal miners in many parts of the Global South . Like all mining, human rights and environmental issues are common in the gold mining industry, and can result in environmental conflict . In mines with less regulation, health and safety risks are much higher. The exact date that humans first began to mine gold
15458-467: The surrounding rock or sediments. Unlike hard-rock mining, which involves excavating solid rock formations, water or dredging is used to extract the gold. Using a sluice box to extract gold from placer deposits has long been a very common practice in prospecting and small-scale mining. Sluices work on the principle that heavier particles will sink to the bottom of a stream, while those that are lighter will be carried downstream and expelled. A sluice box
15589-477: The two rivers sometimes joined the other, flowing to various outlets. The Rio Hondo sometimes changed course to join the San Gabriel River; alternatively, the San Gabriel sometimes shifted course into the Rio Hondo, merging into a single watershed with the Los Angeles River. Whittier Narrows Dam controls the outflow from both rivers into their artificially fixed channels. During storms, water is distributed based on
15720-651: The valley's relatively steep slope. Past the Santa Fe Dam – which when dry is used as the Santa Fe Dam Recreation Area – the river flows through Irwindale , where it is the site of several major gravel quarries, which have operated in the San Gabriel Valley since the early 1900s to mine the rich alluvial sediments deposited by the river over millennia. From here Interstate 605 , the San Gabriel River Freeway, parallels
15851-515: The water gap of the Whittier Narrows. Composed of ancient, highly fractured and unstable crystalline rock, the San Gabriel mountains are subject to tremendous amounts of erosion. Rapid erosion caused by heavy winter storms has created the dramatic canyons of the San Gabriel River. In the headwaters, streams often follow fault traces; the West Fork and part of the East Fork run along the San Gabriel Canyon Fault, which extends in
15982-458: The water used in southeast Los Angeles County today comes from the river. The upper San Gabriel has been intermittently mined for gold since the 1860s, and its deep gravel bed has been an important source of construction aggregate since the early 1900s. The river is also a popular recreation area, with parks and trails in the many flood basins along its course. The headwaters of the San Gabriel River have retained their natural character and are
16113-507: The western United States, this has caused a large amount of tinder and debris to accumulate, increasing the risk of fire. Drought conditions in the first decade of the 21st century led to huge fires much larger than would have occurred naturally. In 2002, the Curve Fire burned 20,000 acres (8,100 ha), much of it in the North Fork of the San Gabriel River, closing Crystal Lake Recreation Area for several years. The 2009 Station Fire ,
16244-410: The western half of the San Gabriel Valley, approaching the San Gabriel River at the Whittier Narrows; south of there, it swings to the southwest and joins the Los Angeles River . In the Whittier Narrows, they are connected by a short channel through which water can flow in both directions. The Rio Hondo is generally considered a separate stream and tributary to the Los Angeles River , but historically
16375-601: The world's gold. Sometimes open-pit mining is used, such as at the Fort Knox Mine in central Alaska. Barrick Gold Corporation has one of the largest open-pit gold mines in North America located on its Goldstrike mine property in north eastern Nevada. Other gold mines use underground mining, where the ore is extracted through tunnels or shafts. South Africa has the world's deepest hard rock gold mine up to 3,900 metres (12,800 ft) underground. At such depths,
16506-720: The world, the Grasberg mine in Papua, Indonesia, is primarily a copper mine. Gold panning , or simply panning , is a form of placer mining and traditional mining that extracts gold from a placer deposit using a pan. The process is one of the simplest ways to extract gold, and is popular with geology enthusiasts especially because of its low cost and relative simplicity. The first recorded instances of placer mining are from ancient Rome , where gold and other precious metals were extracted from streams and mountainsides using sluices and panning ( ruina montium ). Placer mining
16637-663: Was China with 368.3 tonnes of gold mined in that year. The second-largest producer of gold was Russia where 331.1 tonnes was mined in the same year, followed by Australia with 327.8 tonnes. In 2023, the annual gold demand of 4,448 tonnes was 5% below that of 2022. The total gold demand in 2023 was the highest at 4,899 tonnes. Despite its decreasing content in ores, gold production is increasing. This increase can be achieved through ever larger-scale industrial installations as well as innovations, especially in hydrometallurgy . Hard rock mining extracts gold encased in rock, rather than fragments in loose sediment, and produces most of
16768-514: Was discovered in 1961. Official estimates indicate that total world gold production since the beginning of civilization has been around 6,352,216,000 troy ounces (197,576.0 t) and total gold production in Nevada is 1.1% of that, ranking Nevada as one of the Earth's primary gold-producing regions. World gold production was 3,612 tonnes in 2022. As of 2020 , the world's largest gold producer
16899-626: Was mined extensively. The ancient Sumerians , around 2500 BCE, developed sophisticated techniques for extracting gold from alluvial deposits and underground mines. These techniques included the use of sluice boxes. Evidence suggests that Nubia had sporadic access to gold nuggets during the Neolithic and Prehistoric Period . Gold mining in Egypt involved both surface mining such as panning for gold in riverbeads and underground mining, where tunnels were dug to extract gold-bearing quartz veins. During
17030-505: Was removed from the San Gabriel River. Mining along the San Gabriel River began with simple gold panning, but soon developed to more advanced methods. Flumes were constructed to carry water to sluices , long toms, and hydraulic mining operations that separated gold from river gravel; dams and waterwheels helped maintain the necessary head to drive these extensive waterworks and clear the riverbed so that gold-bearing sands could be excavated. Some hard rock (tunnel) mining also occurred in
17161-428: Was used by the U.S. Navy as a torpedo test site; the concrete launch ramp remains today and is easily seen from Highway 39, which runs through the canyon. The river emerges from the San Gabriel Canyon at Azusa , a short distance below Morris Dam , where it reaches the wide and gently sloping alluvial plain of the San Gabriel Valley . At the mouth of the canyon, the entire flow of the river, except during wet seasons,
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