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45-624: Tory Channel (officially Tory Channel / Kura Te Au ) is one of the drowned valleys that form the Marlborough Sounds in New Zealand. Inter-island ferries normally use it as the principal channel between Cook Strait and the Marlborough Sounds. Tory Channel lies to the south of Arapaoa Island , separating it from the mainland. At its western end it joins the larger Queen Charlotte Sound , which it meets halfway along

90-630: A comparative analysis of various land subsidence monitoring techniques. The results indicated that InSAR offered the highest coverage, lowest annual cost per point of information and the highest point density. Additionally, they found that, aside from continuous acquisition systems typically installed in areas with rapid subsidence, InSAR had the highest measurement frequencies. In contrast, leveling, non-permanent GNSS, and non-permanent extensometers generally provided only one or two measurements per year. These methods project future land subsidence trends by extrapolating from existing data, treating subsidence as

135-459: A function solely of time. The extrapolation can be performed either visually or by fitting appropriate curves. Common functions used for fitting include linear, bilinear, quadratic, and/or exponential models. For example, this method has been successfully applied for predicting mining-induced subsidence. These approaches evaluate land subsidence based on its relationship with one or more influencing factors, such as changes in groundwater levels,

180-431: A number of years, a cumulative drying occurs as the tree grows. That can lead to the opposite of subsidence, known as heave or swelling of the soil, when the tree declines or is felled. As the cumulative moisture deficit is reversed, which can last up to 25 years, the surface level around the tree will rise and expand laterally. That often damages buildings unless the foundations have been strengthened or designed to cope with

225-489: A result of increased effective stress . In this way, land subsidence has the potential of becoming self-perpetuating, having rates up to 5 cm/yr. Water management used to be tuned primarily to factors such as crop optimization but, to varying extents, avoiding subsidence has come to be taken into account as well. When differential stresses exist in the Earth, these can be accommodated either by geological faulting in

270-532: A total of over 50 reserves in the area. The sounds were extensively travelled and partly inhabited by Māori groups before the coming of the Europeans, using the sounds as shelter from bad weather and partaking of the rich food sources. Māori were also known to carry their canoes over some stretches of land on portage paths. However, as in most areas of the South Island, populations were smaller than in

315-559: Is a major arm of Queen Charlotte Sound, and between them, the Channel and the Sound isolate the hills of Arapaoa Island from the mainland. Other major islands in the sounds include D'Urville Island . The Sounds are home to the entire breeding population of the rare and vulnerable rough-faced shag (also known as the New Zealand king cormorant) which nests on a small number of rocky islets there. The Department of Conservation manages

360-416: Is at the northern terminus of the South Island's main railway and state highway networks. The main small-boat port, Waikawa , is one of New Zealand's largest and provides a base for leisure sailors and vacationers. The main sounds, other than Queen Charlotte Sound, are Pelorus Sound / Te Hoiere and Kenepuru Sound . Havelock is a small port town at the head of Pelorus Sound / Te Hoiere . Tory Channel

405-569: Is increasingly common, having started in the 1960s. However, the wakes caused by fast catamaran vehicular ferry services to the North Island have allegedly damaged farms and destroyed crab grounds. They were also blamed for stripping the local beaches bare of sand, and damaging landings and other facilities built close to the water's edge. This resulted in a dispute heard in the New Zealand Environment Court in

450-451: Is relatively predictable in its magnitude, manifestation and extent, except where a sudden pillar or near-surface tunnel collapse occurs (usually very old workings ). Mining-induced subsidence is nearly always very localized to the surface above the mined area, plus a margin around the outside. The vertical magnitude of the subsidence itself typically does not cause problems, except in the case of drainage (including natural drainage)–rather, it

495-415: Is the associated surface compressive and tensile strains, curvature, tilts and horizontal displacement that are the cause of the worst damage to the natural environment, buildings and infrastructure. Where mining activity is planned, mining-induced subsidence can be successfully managed if there is co-operation from all of the stakeholders. This is accomplished through a combination of careful mine planning,

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540-582: The Earth's crust by tectonic forces. Subsidence resulting from tectonic deformation of the crust is known as tectonic subsidence and can create accommodation for sediments to accumulate and eventually lithify into sedimentary rock . Ground subsidence is of global concern to geologists , geotechnical engineers , surveyors , engineers , urban planners , landowners, and the public in general. Pumping of groundwater or petroleum has led to subsidence of as much as 9 meters (30 ft) in many locations around

585-459: The Ministry of Fisheries has also noted that only 6% of the sounds are set aside for the dredging, though this had been much more extensive in the past. The main channels of the Marlborough Sounds have calm water and are popular for sailing . Cook Strait , however, is infamous for its strong currents and rough waters, especially when the wind is from the south or north. Because of this, some of

630-468: The North Island. European history of the area is considered to start with Captain Cook 's visit to the sounds in the 1770s, discovering a plant ( Cook's scurvy grass ) high in vitamin C which helped to cure scurvy amongst his crew. On Motuara Island , Cook also proclaimed British sovereignty over the South Island. Some parts of the sounds also later developed a significant whaling history, and much of

675-650: The Tory Channel for their baleen and whale oil . Tory Channel was accurately surveyed in 1840 and named after the New Zealand Company ship Tory , a pioneer ship that brought British colonists to Wellington . Around this time, whaling stations were already operating in Te Awaiti Bay. Between 1911 and 1964, the Perano family hunted whales from Whekenui Bay. Humpback whales were spotted from

720-409: The area. The subsidence was brought to a halt when secondary recovery wells pumped enough water into the oil reservoir to stabilize it. Land subsidence can occur in various ways during an earthquake. Large areas of land can subside drastically during an earthquake because of offset along fault lines. Land subsidence can also occur as a result of settling and compacting of unconsolidated sediment from

765-422: The asthenosphere. If mass is added to a local area of the crust (e.g., through deposition ), the crust subsides to compensate and maintain isostatic balance . The opposite of isostatic subsidence is known as isostatic rebound —the action of the crust returning (sometimes over periods of thousands of years) to a state of isostacy, such as after the melting of large ice sheets or the drying-up of large lakes after

810-401: The brittle crust , or by ductile flow in the hotter and more fluid mantle . Where faults occur, absolute subsidence may occur in the hanging wall of normal faults. In reverse, or thrust, faults, relative subsidence may be measured in the footwall. The crust floats buoyantly in the asthenosphere , with a ratio of mass below the "surface" in proportion to its own density and the density of

855-414: The channel, turning the water red. Kurahaupō and Rangitāne give the meaning "the red current" for Kura Te Au. James Cook anchored several times in the nearby bay he named Ship Cove . He sighted the Tory Channel in an excursion on the pinnace from his ship HMS Resolution on 5 November 1774. John Guard established the first permanent whaling station on Arapaoa Island in 1827, targeting whales in

900-555: The early 1990s, brought forward by the 'Guardians of the Sounds' group. The court, however, not only refused to restrict the fast ferries but also awarded NZ$ 300,000 in court costs against the citizen group which had brought the case. This was seen as a strong blow against civic action, and a curtailing of the powers of the Resource Management Act . However, as damage increasingly became visible, and protests continued,

945-507: The effect. High buildings can create land subsidence by pressing the soil beneath with their weight. The problem is already felt in New York City , San Francisco Bay Area , Lagos . Land subsidence leads to the lowering of the ground surface, altering the topography. This elevation reduction increases the risk of flooding , particularly in river flood plains and delta areas. Earth fissures are linear fractures that appear on

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990-524: The electricity network. Other designs envisaged up to 50 turbines, but there are uncertainties about flow rates, the area is about 15 km (9.3 mi) from the HVDC Inter-Island transmission station at Ōraumoa / Fighting Bay and a calculation in 2013 suggested that an economic return was unlikely. Marlborough Sounds The Marlborough Sounds ( te reo Māori : Te Tauihu-o-te-Waka ) are an extensive network of sea-drowned valleys at

1035-673: The excessive extraction of groundwater, making it a growing problem throughout the world. Groundwater fluctuations can also indirectly affect the decay of organic material. The habitation of lowlands , such as coastal or delta plains, requires drainage . The resulting aeration of the soil leads to the oxidation of its organic components, such as peat , and this decomposition process may cause significant land subsidence. This applies especially when groundwater levels are periodically adapted to subsidence, in order to maintain desired unsaturated zone depths, exposing more and more peat to oxygen. In addition to this, drained soils consolidate as

1080-402: The fast ferries (which only operated for the summer season) were eventually restricted to a lower speed of 18 knots in the sounds (officially for safety reasons), reducing their time advantage over the conventional ferries. They have since been discontinued. In July/August 2007, the 'Guardians of the Sounds' environmentalist group planned a 100-ship flotilla protest against scallop dredging in

1125-521: The ground level. Since exploitation of the Slochteren ( Netherlands ) gas field started in the late 1960s the ground level over a 250 km area has dropped by a current maximum of 30 cm. Extraction of petroleum likewise can cause significant subsidence. The city of Long Beach, California , has experienced 9 meters (30 ft) over the course of 34 years of petroleum extraction, resulting in damage of over $ 100 million to infrastructure in

1170-666: The hills at the Tory Channel entrance during their migration through Cook Strait. The Perano Whaling Station was the last whaling operation in New Zealand and closed in 1964. The name of the channel was officially altered to Tory Channel / Kura Te Au in August 2014. Energy Pacifica planned to install up to ten underwater tidal stream turbines , each able to produce up to 1.2 MW, near the Cook Strait entrance to Tory Channel. They claimed Tory Channel had tidal flows of 3.6 metres per second (12 ft/s) with good bathymetry and access to

1215-402: The land surface, characterized by openings or offsets. These fissures can be several meters deep, several meters wide, and extend for several kilometers. They form when the deformation of an aquifer, caused by pumping, concentrates stress in the sediment. This inhomogeneous deformation results in the differential compaction of the sediments. Ground fissures develop when this tensile stress exceeds

1260-443: The last ice age. Lake Bonneville is a famous example of isostatic rebound. Due to the weight of the water once held in the lake, the earth's crust subsided nearly 200 feet (61 m) to maintain equilibrium. When the lake dried up, the crust rebounded. Today at Lake Bonneville , the center of the former lake is about 200 feet (61 m) higher than the former lake edges. Many soils contain significant proportions of clay. Because of

1305-407: The latter's length. Its eastern end meets Cook Strait close to the strait's narrowest point. The Channel is 16.8 km (10.4 mi) long, averages 1.1 km (0.68 mi) in width, and is up to 65 m (213 ft) deep, with an average channel depth of 39.2 m (129 ft). Tory Channel forms a substantial part of the ferry route between Wellington and Picton . Erosion attributed to

1350-570: The narrow channels closer to the Strait are dangerous to navigate. Notable amongst these is French Pass at the southern end of D'Urville Island, which has several vortices . The most notable shipwreck in the sounds is that of the Russian cruise liner MS Mikhail Lermontov , which sank in 1986 in Port Gore , close to the mouth of Queen Charlotte Sound, after colliding with rocks. One crew member

1395-502: The northern end of the South Island of New Zealand. The Marlborough Sounds were created by a combination of land subsidence and rising sea levels . According to Māori mythology , the sounds are the prows of the many sunken waka of Aoraki . Covering some 4,000 km (1,500 sq mi) of sounds, islands, and peninsulas, the Marlborough Sounds lie at the South Island's north-easternmost point, between Tasman Bay in

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1440-525: The shaking of an earthquake. The Geospatial Information Authority of Japan reported immediate subsidence caused by the 2011 Tōhoku earthquake . In Northern Japan, subsidence of 0.50 m (1.64 ft) was observed on the coast of the Pacific Ocean in Miyako , Tōhoku , while Rikuzentakata, Iwate measured 0.84 m (2.75 ft). In the south at Sōma, Fukushima , 0.29 m (0.95 ft)

1485-488: The sounds was (thinly) settled by European farmers in the late 19th and early 20th century. The Marlborough Sounds are connected to Cook Strait at the north-east extreme. At this point, the North Island is at its closest to the South Island, and the inter-island road, rail, and passenger ferry service between Picton and Wellington travels through the sounds. Marine farming, especially of salmon and mussels ,

1530-399: The sounds, which they consider damages the ecosystem of the sounds similar to bottom trawling in the open sea. The protest was intended to call attention to what they allege is the Ministry of Fisheries ignoring the detrimental effect of the practice. Commercial scallops harvesting companies have warned that protests could endanger lives if the protesters engaged in dangerous manoeuvres, while

1575-620: The subsurface creates voids (i.e., caves ). If the roof of a void becomes too weak, it can collapse and the overlying rock and earth will fall into the space, causing subsidence at the surface. This type of subsidence can cause sinkholes which can be many hundreds of meters deep. Several types of sub-surface mining , and specifically methods which intentionally cause the extracted void to collapse (such as pillar extraction, longwall mining and any metalliferous mining method which uses "caving" such as "block caving" or "sub-level caving") will result in surface subsidence. Mining-induced subsidence

1620-405: The taking of preventive measures, and the carrying out of repairs post-mining. If natural gas is extracted from a natural gas field the initial pressure (up to 60 MPa (600 bar )) in the field will drop over the years. The pressure helps support the soil layers above the field. If the gas is extracted, the overburden pressure sediment compacts and may lead to earthquakes and subsidence at

1665-595: The tensile strength of the sediment. Land subsidence can lead to differential settlements in buildings and other infrastructures , causing angular distortions. When these angular distortions exceed certain values, the structures can become damaged, resulting in issues such as tilting or cracking. Land subsidence causes vertical displacements (subsidence or uplift). Although horizontal displacements also occur, they are generally less significant. The following are field methods used to measure vertical and horizontal displacements in subsiding areas: Tomás et al. conducted

1710-441: The very small particle size, they are affected by changes in soil moisture content. Seasonal drying of the soil results in a lowering of both the volume and the surface of the soil. If building foundations are above the level reached by seasonal drying, they move, possibly resulting in damage to the building in the form of tapering cracks. Trees and other vegetation can have a significant local effect on seasonal drying of soils. Over

1755-665: The volume of groundwater extraction , and clay content. This model assumes that changes in piezometric levels affecting aquifers and aquitards occur only in the vertical direction. It allows for subsidence calculations at a specific point using only vertical soil parameters. Quasi-three-dimensional seepage models apply Terzaghi 's one-dimensional consolidation equation to estimate subsidence, integrating some aspects of three-dimensional effects. The fully coupled three-dimensional model simulates water flow in three dimensions and calculates subsidence using Biot's three-dimensional consolidation theory. Machine learning has become

1800-451: The wake from the ferries, particularly the new faster ones (discontinued in 2005), has resulted in speed restrictions. One of the two candidates for the easternmost point in the South Island (along with Cape Campbell ) lies at the entrance of Tory Channel. It is called West Head. Te Āti Awa and Ngāti Tama recognize the channel Kura Te Au as an important historic mahinga kai (food source), and settlement for Te Āti Awa . The channel

1845-404: The west and Cloudy Bay in the south-east. The almost fractal coastline has 1/10 of the length of New Zealand's coasts. The steep, wooded hills and small quiet bays of the sounds are sparsely populated, as access is difficult. Many of the small settlements and isolated houses are only accessible by boat. The main large port is Picton on the mainland, at the head of Queen Charlotte Sound . It

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1890-413: The world and incurring costs measured in hundreds of millions of US dollars. Land subsidence caused by groundwater withdrawal will likely increase in occurrence and related damages, primarily due to global population and economic growth, which will continue to drive higher groundwater demand. Subsidence frequently causes major problems in karst terrains, where dissolution of limestone by fluid flow in

1935-512: Was killed in the disaster. The ship herself is now a popular dive wreck . 41°08′30″S 174°05′22″E  /  41.14167°S 174.08944°E  / -41.14167; 174.08944 Subsidence Processes that lead to subsidence include dissolution of underlying carbonate rock by groundwater ; gradual compaction of sediments ; withdrawal of fluid lava from beneath a solidified crust of rock; mining; pumping of subsurface fluids, such as groundwater or petroleum ; or warping of

1980-672: Was observed. The maximum amount of subsidence was 1.2 m (3.93 ft), coupled with horizontal diastrophism of up to 5.3 m (17.3 ft) on the Oshika Peninsula in Miyagi Prefecture . Groundwater-related subsidence is the subsidence (or the sinking) of land resulting from groundwater extraction. It is a growing problem in the developing world as cities increase in population and water use, without adequate pumping regulation and enforcement. One estimate has 80% of serious land subsidence problems associated with

2025-405: Was used as a primary highway by Te Āti Awa , and is still monitored and defended by the iwi in the environmental courts. The name Kura Te Au originates from the red colour of the sea caused by a variety of plankton and the high populations of crustacean krill. According to legend, Kura Te Au is where Kupe killed the giant, mythical octopus, Te Wheke-a-Muturangi , causing its blood to run through

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