Great Gibraltar Sand Dune

Great Gibraltar Sand Dune
Great Gibraltar Sand Dune
	View of the dune and eastern Mediterranean coast of Gibraltar from the Rock of Gibraltar.
	Location of the Great Sand Dune within Gibraltar.
Coordinates	36°08′03″N5°20′36″W / 36.134166°N 5.343221°W Coordinates: 36°08′03″N5°20′36″W / 36.134166°N 5.343221°W
Age	Pleistocene
Topo map	OS Gibraltar

Last updated October 01, 2019

The Great Gibraltar Sand Dune is an ancient sand dune in the British Overseas Territory of Gibraltar. It forms part of the Upper Rock Nature Reserve and dominates the eastern cliffs of the Rock of Gibraltar. It was once used to capture rainwater which was contained in underground tanks within the Rock to satisfy the population's potable water needs.

In physical geography, a dune is a hill of loose sand built by aeolian processes (wind) or the flow of water. Dunes occur in different shapes and sizes, formed by interaction with the flow of air or water. Most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter "slip face" in the lee side. The valley or trough between dunes is called a slack.

The British Overseas Territories (BOTs) or United Kingdom Overseas Territories (UKOTs) are fourteen territories under the jurisdiction and sovereignty of the United Kingdom. They are remnants of the British Empire that have not been granted independence or have voted to remain British territories. These territories do not form part of the United Kingdom and, with the exception of Gibraltar, are not part of the European Union. Most of the permanently inhabited territories are internally self-governing, with the UK retaining responsibility for defence and foreign relations. Three are inhabited only by a transitory population of military or scientific personnel. They all share the British monarch as head of state.

Gibraltar is a British Overseas Territory located at the southern tip of the Iberian Peninsula. It has an area of 6.7 km² (2.6 sq mi) and is bordered to the north by Spain. The landscape is dominated by the Rock of Gibraltar at the foot of which is a densely populated town area, home to over 32,000 people, primarily Gibraltarians.

Geology

The prehistoric dune is made from yellow, windblown sands lacking the red component of the sands on the west side of the Rock. It is made of the same sand that once formed part of a vast savanna of the late Pleistocene where Neanderthals hunted.^[1] The levant winds of prehistory continuously blew sand from this savanna westwards, accumulating against the eastern cliffs of the Rock, reaching from the base of the cliff right down to sea level (at that time there was no road where Sir Herbert Miles Road is today).^[1] The occasional rockfall from the precipice above added boulders to the dune so the formation seen today is a consolidated composite of rocks and windblown sands. The upper limits of the dune were scarped by the British garrison for two reasons - to avoid soldiers deserting the place and to prevent surprise attacks by Spanish troops. The Great Sand Dune was constantly shifting right up to the late 19th century when corrugated iron sheets were laid over the dune for the collection of rainwater.^[1] John White described this and the efforts to make it inaccessible:

A savanna or savannah is a mixed woodland-grassland ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses.

The Pleistocene is the geological epoch which lasted from about 2,580,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.

Neanderthals are an extinct species or subspecies of archaic humans in the genus Homo, who lived within Eurasia from circa 400,000 until 40,000 years ago.

"The Eastern side of the hill consists of an immense sloping bank of whitish sand interspersed with huge fragments of rock, and reaching from the sea nearly to the summit of the rock in some parts not far from the Signal House, and the Middle-hill Guards. These parts were formerly accessible, which made it necessary to keep constant guards there, as well to prevent desertions from within as a surprise from without. Of late years, much labour has been bestowed in making all these parts more abrupt and difficult, yet it is still necessary to watch them, as there are always some hardy adventurers who will wantonly risk their lives down these perilous cliffs, either in attempting to desert or in search of flowers."^[1]
Signal Hill Battery or Signal Battery was an artillery battery in the British Overseas Territory of Gibraltar. The battery was mounted high on the rock. Little remains today as the Gibraltar Cable Car top station was built on the site of the old battery.
Middle Hill Battery is an artillery battery in the British Overseas Territory of Gibraltar. It is located on Middle Hill, at the northeastern end of the Upper Rock Nature Reserve, just south of Green's Lodge Battery and Rock Gun Battery. The emplacement dates to 1727, when a single gun was mounted. By the turn of the twentieth century, six 10-inch rifled muzzle-loading guns were present at Middle Hill Battery. Other buildings documented at that time as part of the battery complex included the Nursery Hut and the Middle Hill Group, the latter a cluster of buildings which perched on the cliff edge. An anti-aircraft Bofors gun had been installed at the battery by the Second World War. After the war, the area transitioned to use as a Ministry of Defence aerial farm. In 2005, the battery and surrounding area were transferred to the Government of Gibraltar. The site is now managed by the Gibraltar Ornithological and Natural History Society.

Water catchments

Gibraltar has few natural sources of fresh water which has been historically problematic for its population over the centuries. In 1898, the construction on the waterworks began with the construction of four 5,000,000 imperial gallons (23,000,000 l) reservoirs cut inside the western side of the Rock at an elevation of 103.6 metres (340 ft) above sea level, each being 60.96 metres (200.0 ft) long 15.24 metres (50.0 ft) high and with an average width of 6.1 metres (20 ft), with a total capacity of 22,727 square metres (244,630 sq ft). They were officially inaugurated by Governor of Gibraltar Sir George White in 1901. These reservoirs were initially fed by relatively small water catchment areas on the western side of the Rock above the Moorish Castle.^[2]^[3]

Fresh water is any naturally occurring water except seawater and brackish water. Fresh water includes water in ice sheets, ice caps, glaciers, icebergs, bogs, ponds, lakes, rivers, streams, and even underground water called groundwater. Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. Though the term specifically excludes seawater and brackish water, it does include mineral-rich waters such as chalybeate springs.

The Governor of Gibraltar is the representative of the British monarch in the British overseas territory of Gibraltar. The governor is appointed by the monarch on the advice of the British Government. The role of the governor is to act as the de facto head of state, and he is responsible for formally appointing the Chief Minister of Gibraltar, along with other members of the Government of Gibraltar after a general election. The governor serves as commander-in-chief of Gibraltar's military forces and has sole responsibility for defence and security.

Field Marshal Sir George Stuart White, was an officer of the British Army. He was stationed at Peshawar during the Indian Mutiny and then fought at the Battle of Charasiab in October 1879 and at the Battle of Kandahar in September 1880 during the Second Anglo-Afghan War. For his bravery during these two battles, he was awarded the Victoria Cross. He went on to command a brigade during the Third Anglo-Burmese War in 1886 and became commander of Quetta District in 1889 in which role he led operations in the Zhob Valley and in Balochistan. He was commander of the forces in Natal at the opening of the Second Boer War and fought at the Battle of Elandslaagte in October 1899. He commanded the garrison at the Siege of Ladysmith: although instructed by General Sir Redvers Buller to surrender the garrison he responded "I hold Ladysmith for the Queen" and held out for another four months before being relieved in February 1900. He finished his career as Governor of Gibraltar and then as Governor of the Royal Hospital Chelsea.

As Gibraltar's population and demand for a fresh water supply increased, further sources of supply were required and a scheme to expand the system was proposed and carried out. This consisted of the construction of a 40,000 square metres (4.0 ha) water catchment area on the east side of the Rock and the driving of an 800 metres (2,600 ft) tunnel through the Rock running east-west to channel the water to the existing reservoirs. The catchment which was the original idea of the then City Engineer of Gibraltar and was constructed in 1903 on the Great Sand Dune which has an average inclination of 1⅓ to 1. The largest of the boulders embedded in the dune were blasted away in order to trim the surface as even as possible. A footpath and channel for the collection of rainwater were constructed along the lower perimeter of the catchment area. Timber piles 1,500 millimetres (59 in) x 150 millimetres (5.9 in) x 40 millimetres (1.6 in) were driven their full length into the smoothed dune. To these a timber framing of 75 millimetres (3.0 in) x 75 millimetres (3.0 in) x 4,500 millimetres (180 in) purlins and 75 millimetres (3.0 in) x 75 millimetres (3.0 in) x 2,400 millimetres (94 in) rafters were nailed to them which was followed by screwing corrugated galvanised iron sheets 2,400 millimetres (94 in) x 900 millimetres (35 in) round the edges. The timber had been previously pressure treated with creosote at a pressure of 170 pounds per square inch (1,200 kPa). Further expansions of the Great Sand Dune catchments were carried out in stages up until 1961.^[2] The original plan was to cover an area of 10 acres (40,000 m²). Between 1911 and 1914 a fifth reservoir was excavated inside the Rock and the catchment area increased to 24 acres (97,000 m²). By 1961 the total catchment area had increased to its maximum of 34 acres (140,000 m²).^[2] It took roughly 5,928 rafters, 1,112 purlins, 1,161 piles, 5,928 sheets, 2,920 kg of screws and 850 kg of washers for every hectare of the Great Dune that was covered.

A drainage basin is any area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or other body of water. The drainage basin includes all the surface water from rain runoff, snowmelt, and nearby streams that run downslope towards the shared outlet, as well as the groundwater underneath the earth's surface. Drainage basins connect into other drainage basins at lower elevations in a hierarchical pattern, with smaller sub-drainage basins, which in turn drain into another common outlet.

Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material - a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.

In architecture, structural engineering or building, a purlin is any longitudinal, horizontal, structural member in a roof except a type of framing with what is called a crown plate. In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin and common purlin.

Other uses

The Great Dune served to maintain a regular supply of sand on the eastern beaches of Gibraltar, especially Sandy Bay particularly when the sea removed material from the beach. This dynamic nature meant that little vegetation of any significant height could grow on the dune with any permanence as many pre-catchment photographs demonstrate.^[1]

Sandy Bay is a village located on a small bay on the eastern Mediterranean coast of Gibraltar, on the opposite side of The Rock from the main city. It is situated to the south of Catalan Bay and is accessible via Sir Herbert Miles Road.

In 2001, the Gibraltar Ornithological and Natural History Society began to manage the phased work of dismantling the catchment construction. By 2006 the slope was entirely restored to its natural state and is now completely covered in vegetation native to the habitat of Gibraltar.^[2]^[4]

Related Research Articles

Rainwater harvesting is the accumulation and storage of rainwater for reuse on-site, rather than allowing it to run off. Rainwater can be collected from rivers or roofs, and in many places, the water collected is redirected to a deep pit, aquifer, a reservoir with percolation, or collected from dew or fog with nets or other tools. Its uses include water for gardens, livestock, irrigation, domestic use with proper treatment, indoor heating for houses, etc. The harvested water can also be used as drinking water, longer-term storage, and for other purposes such as groundwater recharge.

Mount's Bay is a large, sweeping bay on the English Channel coast of Cornwall, United Kingdom, stretching from the Lizard Point to Gwennap Head. In the north of the bay, near Marazion, is St Michael's Mount; the origin of name of the bay. In summer, it is a large, benign, scenic, natural harbour. However, in winter, onshore gales present maritime risks, particularly for sailing ships. There are more than 150 known wrecks from the nineteenth century in the area. The eastern side of the bay centred around Marazion and St Michael's Mount was designated as a Marine Conservation Zone in January 2016.

The Badain Jaran Desert is a desert in China which spans the provinces of Gansu, Ningxia and Inner Mongolia. It covers an area of 49,000 square kilometers. By size it is the third largest desert in China.

The Stephens Creek Dam is an earth-filled embankment dam built on a rock foundation with an uncontrolled spillway across the Stephens Creek, located in the Far West region of New South Wales, Australia. The principal purpose of the dam is to supply potable water for the town of Broken Hill. The impounded 2,000-megalitre reservoir is called Stephens Creek Reservoir.

The Wivenhoe Dam is a rock and earth-fill embankment dam with a concrete spillway across the Brisbane River in South East Queensland, Australia. The dam wall is located about 80 kilometres (50 mi) by road from the centre of Brisbane. The primary purpose of the dam is the supply of potable water for the Brisbane and Ipswich regions. In addition, the dam also provides for flood mitigation control, hydroelectricity and for recreation. The impounded reservoir is called Lake Wivenhoe and the dam, the lake and a narrow strip of surrounding land forms a locality also called Lake Wivenhoe.

Mangrove Creek Dam, a concrete faced concrete faced rockfill embankment dam, is the primary reservoir for water supply to residents of the Central Coast in New South Wales, Australia.

Langsett Reservoir is in Yorkshire, England, near the villages of Langsett and Upper Midhope, on the edge of the Peak District National Park. The reservoir was constructed between 1898 and 1904, and is now managed by Yorkshire Water. Fed by the Little Don or Porter River, it is around a mile long, and supplies water for Sheffield and Barnsley via the Langsett Treatment Works.

Lake Qaraoun is an artificial lake or reservoir located in the southern region of the Beqaa Valley, Lebanon. It was created near Qaraoun village in 1959 by building a 61-metre-high (200 ft) concrete-faced rockfill dam in the middle reaches of the Litani River. The reservoir has been used for hydropower generation, domestic water supply, and for irrigation of 27,500 hectares.

Split Rock Dam is a minor ungated concrete faced rock fill embankment dam with concrete chute spillway across the Manilla River upstream of Manilla in the north-western slopes region of New South Wales, Australia. The dam's purpose includes flood mitigation, irrigation, water supply and conservation. The impounded reservoir is called Split Rock Reservoir.

Oleshky Sands is the largest expanse of sand in Ukraine. It is situated inland from the Ukrainian coast of the Black Sea and consists of sand dunes or kuchuhury (locally), which reach a height of five meters. Some sparse vegetation can be located across the sands.

The Watts River is a perennial river of the Port Phillip and Western Port catchment, located near Healesville, in the Central Victoria region of the Australian state of Victoria.

The Daecheong Dam is a combination concrete gravity and embankment dam on the Geum River, 16 km (10 mi) north of Daejeon in South Korea. The multi-purpose dam provides benefits of flood control, water supply and hydroelectric power generation. Construction on the dam began in 1975 and was formally commissioned on 1 December 1980. The 72 m (236 ft) high rock-fill dam has a central clay core and has created a reservoir with storage of 1,490,000,000 m³ (1,207,963 acre⋅ft).

Ibex Cave is a limestone cave on the Rock of Gibraltar which has yielded stone artifacts of Mousterian tradition. It was discovered in 1975. It is so named as an ibex skull was found within the cave which would have been hunted by the Neanderthals of Gibraltar thousands of years ago. Ibex Cave was named and excavated by the Gibraltar Museum in 1994. Its first formal description was in 1999.

The tunnels of Gibraltar were constructed over the course of nearly 200 years, principally by the British Army. Within a land area of only 2.6 square miles (6.7 km²), Gibraltar has around 34 miles (55 km) of tunnels, nearly twice the length of its entire road network. The first tunnels, excavated in the late 18th century, served as communication passages between artillery positions and housed guns within embrasures cut into the North Face of the Rock. More tunnels were constructed in the 19th century to allow easier access to remote areas of Gibraltar and accommodate stores and reservoirs to deliver the water supply of Gibraltar.

Water supply and sanitation in Gibraltar have been major concerns for its inhabitants throughout its history, from medieval times to the present day. The climate of Gibraltar is a mild Mediterranean one with warm dry summers and cool wet winters. Since daily records of rainfall began in 1790, annual rainfall has averaged a mean of 838 millimetres (33.0 in) with the highest volumes in December and the lowest in July. However, most of Gibraltar's small land area is occupied by the Rock of Gibraltar, a limestone outcrop that is riddled with caves and crevices. There are no rivers, streams, or large bodies of water on the peninsula, which is connected to Spain via a narrow sandy isthmus.

The Mukurumudzi Dam is the primary water source for the Kwale Mineral Sands Project which mines titanium and zircon minerals from the dunes in the area south of Mombasa, Kenya. The Kwale Project is operated by the Australian mining company, Base Resources, and is located 10 kilometres inland from the Kenyan coast and 50 kilometres south of Mombasa, Kenya's principal port facility.

The Moghra Oasis is an uninhabited oasis in the northeastern part of the Qattara Depression in the Western Desert of Egypt. It has a 4 km² (1.5 sq mi) lake containing brackish water, salt marshes and a swamp with reeds.

The Paraguana xeric scrub (NT1313) is an ecoregion in Venezuela to the north and east of Lake Maracaibo along the Caribbean coast. The region holds flora and fauna adapted to the very dry conditions of the coastal dunes and inland areas of bush, scrub, briars and cacti. There are several endangered species of animals and birds. Efforts at protecting the environment have been ineffective. Most of the original trees have been cut down, dunes are being destabilized by loss of vegetation, scrub is replaced by farmland and vegetation is destroyed by grazing goats.

The Raak Plain Boinka is a wilderness area in the state of Victoria, Australia. The boinka groundwater discharge complex is a shallow depression within a region of Mallee dune fields, and contains gypsum flats and salinas, pools of salty water that are mainly fed by groundwater. The distinctive flora of the boinka is largely intact and includes several threatened species.

References

1 2 3 4 5 "The Great Gibraltar Sand Dune". Underground-Gibraltar.com. Gibraltar Museum. Archived from the original on 7 May 2013. Retrieved 29 March 2013.
1 2 3 4 Crone, Jim. "Sandy Bay". DiscoverGibraltar.com. Archived from the original on 2012-06-26.
↑ "Gibraltar Water Supply History". AquaGib. Archived from the original on 15 April 2013. Retrieved 6 April 2013.
↑ "Image of successfully re-vegetated dune". GONHS.org. Gibraltar Ornithological and Natural History Society. Archived from the original on 2013-03-17.

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[UG-1] 1 2 3 4 5 "The Great Gibraltar Sand Dune". Underground-Gibraltar.com. Gibraltar Museum. Archived from the original on 7 May 2013. Retrieved 29 March 2013.

[DG-2] 1 2 3 4 Crone, Jim. "Sandy Bay". DiscoverGibraltar.com. Archived from the original on 2012-06-26.

[AG-3] "Gibraltar Water Supply History". AquaGib. Archived from the original on 15 April 2013. Retrieved 6 April 2013.

[4] "Image of successfully re-vegetated dune". GONHS.org. Gibraltar Ornithological and Natural History Society. Archived from the original on 2013-03-17.