| Simi Hills | |
|---|---|
 Main ridge ofSimi Peak, highest summit of the Simi Hills | |
| Highest point | |
| Peak | Simi Peak |
| Elevation | 2,139 ft (652 m) |
| Geography | |
  Simi Hills location of Simi Hills inCalifornia[1] | |
| Country | United States |
| State | California |
| Districts | |
| Range coordinates | 34°13′28.015″N118°43′0.326″W / 34.22444861°N 118.71675722°W /34.22444861; -118.71675722 |
| Topo map | USGS Calabasas |
TheSimi Hills are a low rockymountain range of theTransverse Ranges in easternVentura County and westernLos Angeles County, ofSouthern California, United States.
The range runs mainly north-south, is approximately26 miles (42 km) long by 7 mi (11 km) wide, and reaches a maximum elevation of 2,401 ft (732 m) atSimi Peak.[2]
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The Simi Hills are aligned east-west and run for 26 miles (42 km), and average around 7 mi (11 km) north-south. The Simi Hills are part of the centralTransverse Ranges System.[3] They lie almost entirely within southeasternVentura County, with some southern and easternfoothills within westernLos Angeles County.
The Simi Hills are on the western edge of theSan Fernando Valley. TheSimi Valley lies to the north, and theConejo Valley lies to the southwest. The San Fernando Valley communities ofChatsworth,West Hills, andWoodland Hills are in the eastern hills and adjacent valley floor inLos Angeles city andcounty. The cities ofAgoura Hills andWestlake Village are also located in Los Angeles County, generally southwest of the Simi Hills. The cities ofThousand Oaks (to the west) andSimi Valley city (to the north) are in the hills and adjacent valleys within Ventura County.
The two nearby mountain ranges are: the higherSanta Susana Mountains adjacent on the northeast acrossSanta Susana Pass; and theSanta Monica Mountains running nearby along the south.
The hills provide the complete or partialwatersheds for several year-roundcreeks and numerous seasonal streams. They include Las Virgenes Creek (tributary ofMalibu Creek), Moore's Canyon Creek,Bell Creek, Dayton Creek, Woolsey Canyon Creek, Brandeis Creek, Runkle Canyon Creek,Arroyo Simi, Palo Comado Creek, Cheeseboro Creek, andArroyo Calabasas (northern fork). Bell Creek and Arroyo Calabasas are the headwaters of theLos Angeles River, by name its beginning with theirconfluence in nearbyCanoga Park. 90% of the Santa Susana Field Lab property drains into the Los Angeles River via tributaries.
Peaks in this region includeSimi Peak, 2,403 ft (732 m),[4]Chatsworth Peak, 2,314 ft (700 m),[5] andEscorpión Peak (aka: Castle Peak), 1,475 ft (450 m).
Because of its low elevation, the Simi Hills typically experiencerainy, mild winters.Snow is rare in the Simi Hills, even in the highest areas. Summers are warm and dry andwildfires do occur here. Cool winds from the Pacific Ocean come from theOxnard Plain and blow into the inland areas through theSanta Clara River Valley and theConejo Valley, though some low hills, such asConejo Mountain, block these winds from the Conejo Valley. The Simi Hills further block these winds, which bring cool weather in both summer and winter from theSan Fernando Valley.
The southern lower hills are mostly covered ingrasslands andoak savanna. The northern rocky hills area is primarilychaparralshrubland andoak woodlands. The Simi Hills are part of theCalifornia chaparral and woodlandsecoregion. Theoaks (Quercus spp.) include: theevergreen coastal live oak (Quercus agrifolia), thedeciduous valley oak (Quercus lobata), and the scrub oak (Quercus dumosa).Riparian zone plants includeCalifornia sycamores (Platanus racemosa) andarroyo willows (Salix lasiolepis). Springwildflowers include theredbush monkey flower (Mimulus aurantiacus),Plummer's mariposa lily (Calochortus plummerae), andcanyon sunflower (Encelia californica).poison oak (Toxicodendron diversilobum) is also an important member of thenative plant habitat community here.
The Simi Hills is the principal, and much wider, of only two terrestrialwildlife corridors linking the coastalSanta Monica Mountains with the inlandSanta Susana Mountains,Topatopa Mountains, andSan Gabriel Mountains, all of the transverse ranges fauna community. The Simi Hills are a critical wildlife corridor linkage for the Santa Monica Mountains to these and other Transverse Ranges further east. The undeveloped nativehabitat provides routes that protect larger land wildlife of the Santa Monicas from genetic isolation.[6][7] TheWallis Annenberg Wildlife Crossing is a vegetated overpass spanning theVentura Freeway under construction at Liberty Canyon inAgoura Hills.
Large sections of the Simi Hills are protected by parks and open space preserves.[8]TheSanta Susana Field Laboratory property, a crucial wildlife corridor to the Santa Susanas, has been proposed for public open space parkland after the closed site's cleanup completion.
The population ofred-legged frogs is small and isolated, and was impacted by theWoolsey Fire that swept through the area in November 2018,[9] as were thirteenmountain lions, two of whom (P-64 andP-74) died.[10]
The Simi Hills were inhabited for over 8,000 years byPaleo-indians andChumash-VenturañoNative Americans for settlements and hunting grounds.[11][12] The Chumash had the established village ofHu'wam inCañon del Escorpión (Bell Canyon). It was a multicultural 'crossroads' destination, where Chumash,Tongva, andTataviam peoples traded and lived besideBell Creek belowEscorpión Peak, at the present dayBell Canyon Park.[13][14] This peak in the Simi Hills (aka: Castle Peak) is one of nine alignment points in Chumash territory and is essential to maintaining the balance of the natural world.[15] Upstream were healing springs and are rock outcrop 'grinding stones.' TheBurro Flats Painted Cave, an example of theRock art of the Chumash people, is nearby.[citation needed]
The Juan Bautista de Anza expedition passed through the area in 1769, being the first European sighting of the Simi Hills. The U.S.National Park Service administers theJuan Bautista de Anza National Historic Trail which enters at Moore Canyon inEl Escorpión Park and crosses across the southern Hills throughUpper Las Virgenes Canyon Open Space Preserve and Cheeseboro/Palo Comado Canyon Park to theConejo Valley.[16] In 1845 theland grant forRancho El Escorpión, beside the Peak and named for it, was issued to one Chumash and two Tongva people and a rare instance of Native Americans being grantees, by Mexican GovernorPío Pico. TheRancho El Conejo was to the west, and included that end of the Simi Hills.[citation needed]
In the first half of the 20th century, there were four largemovie ranches in the Simi Hills for filming motion pictures on location. The gated community ofBell Canyon began development of geographic Bell Canyon in the 1968. To the north ofU.S. 101, east ofThousand Oaks, and west ofSimi Valley the early 1960s suburban expansion of metropolitan Los Angeles brought the development of small to significantly sized parcels of land in the Simi Hills. Hillside subdivisions regraded natural contours into terraced lots, changing the Hills viewshed, drainage patterns, and habitats in those areas. The extensive planned new community projects at Jordan Ranch andAhmanson Ranch were eventually stopped by local citizens and theSanta Monica Mountains Conservancy keeping extensive Hills acreage natural in open space parks.[citation needed]
The Simi Hills were home of theRocketdyneSanta Susana Field Laboratory (SSFL) for open-air testing of rocket engines from 1947 to 1990, and the site of experimentalnuclear reactor experiments with fournuclear accidents between 1959 and 1969; these projects and accidents were declassified in 1989. The first accident, in 1959, was the most serious with a full meltdown. The extent of the accident is unknown due to instrument limitations, other than that it released extensive radiation. More radiation was released in the 1959 event than in theThree Mile Island accident 20 years later.[17] The groundwater under portions of the Simi Hills, contaminated with toxins and radionuclides that were also historically used at SSFL, has been and is a key concern in new development decisions and the SSFL property's future limited to parkland use after an impending cleanup, initiating preservation of more open space in the range.[18]
TheRim of the Valley Trail Corridor[19] is in the planning stages and includes the Simi Hills open space parklands and proposed new areas.[20][21][22][23]
This article incorporatespublic domain material fromCalifornia Red-Legged Frogs: Santa Monica Mountains National Recreation Area.National Park Service. RetrievedJuly 12, 2021.{{cite web}}: CS1 maint: archived copy as title (link) SSPSHP Ethnohistory Accessed 2/28/2010
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