A levee, dike, dyke, embankment, floodbank, or stop bank is a structure that is usually earthen and that often runs parallel to the course of a river in its floodplain or along low-lying coastlines.
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone through lithification.
A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high discharge. The soils usually consist of clays, silts, sands, and gravels deposited during floods.
Alluvium is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is typically geologically young and is not consolidated into solid rock. Sediments deposited underwater, in seas, estuaries, lakes, or ponds, are not described as alluvium.
An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but are also found in more humid environments subject to intense rainfall and in areas of modern glaciation. They range in area from less than 1 square kilometer (0.4 sq mi) to almost 20,000 square kilometers (7,700 sq mi).
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used.
An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the smaller area over which the rivers flood at a particular period of time, whereas the alluvial plain is the larger area representing the region over which the floodplains have shifted over geological time.
A polystrate fossil is a fossil of a single organism that extends through more than one geological stratum. The word polystrate is not a standard geological term. This term is typically found in creationist publications.
Parent material is the underlying geological material in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are often classified based upon their contents of consolidated or unconsolidated mineral material that has undergone some degree of physical or chemical weathering and the mode by which the materials were most recently transported.
A crevasse splay is a sedimentary fluvial deposit which forms when a stream breaks its natural or artificial levees and deposits sediment on a floodplain. A breach that forms a crevasse splay deposits sediments in similar pattern to an alluvial fan deposit. Once the levee has been breached the water flows out of its channel. As the water spreads onto the flood plain sediments will start to fall out of suspension as the water loses energy. The resulting deposition can create graded deposits similar to those found in Bouma sequences. In some cases crevasse splays can cause a river to abandon its old river channel, a process known as avulsion. Breaches that form a crevasse splay deposits occur most commonly on the outside banks of meanders where the water has the highest energy. Crevasse splay deposits can range in size. Larger deposits can be 6 m (20 ft) thick at the levee and spread 2 km (1.2 mi) wide, while smaller deposits may only be 1 cm (0.39 in) thick.
In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record. In most cases, the environments associated with particular rock types or associations of rock types can be matched to existing analogues. However, the further back in geological time sediments were deposited, the more likely that direct modern analogues are not available.
In geology, a backswamp is a type of depositional environment commonly found in a floodplain. It is where deposits of fine silts and clays settle after a flood. These deposits create a marsh-like landscape that is often poorly drained and usually lower than the rest of the floodplain.
In sedimentary geology and fluvial geomorphology, avulsion is the rapid abandonment of a river channel and the formation of a new river channel. Avulsions occur as a result of channel slopes that are much less steep than the slope that the river could travel if it took a new course.
An alluvial river is one in which the bed and banks are made up of mobile sediment and/or soil. Alluvial rivers are self-formed, meaning that their channels are shaped by the magnitude and frequency of the floods that they experience, and the ability of these floods to erode, deposit, and transport sediment. For this reason, alluvial rivers can assume a number of forms based on the properties of their banks; the flows they experience; the local riparian ecology; and the amount, size, and type of sediment that they carry.
Citadel Bastion is a rocky, flat-topped, rocky elevation at the south side of the terminus of Saturn Glacier, facing towards George VI Sound and the Rymill Coast, situated on the east side of Alexander Island, Antarctica. Its maximum elevation is about 645 m. Citadel Bastion lies next to Hodgson Lake. This mountain was mapped from trimetrogon air photography taken by the Ronne Antarctic Research Expedition, 1947–48, and from survey by the Falkland Islands Dependencies Survey, 1948–50. The name applied by the UK Antarctic Place-Names Committee because it resembles a fortified structure with a watchtower at the end of a wall.
Vegetation-induced sedimentary structures (VISS) are primary sedimentary structures formed by the interaction of detrital sediment with in situ plants. VISS provide physical evidence of vegetation's fundamental role in mediating sediment accumulation and erosion in clastic depositional environments. VISS can be broken into seven types, five being hydrodynamic and two being decay-related. The simple hydrodynamic VISS are categorized by centroclinal cross strata, scratch semicircles and upturned beds. The complex hydrodynamic VISS are categorized by coalesced scour fills and scour-and-mound beds. The decay-related VISS are categorized by mudstone-filled hollows and downturned beds.
The Bahe Formation is a Late Miocene geological formation in Shaanxi, China. It has "a complex lithology of predominantly orange-yellow conglomerates, sandstones, tan-yellow sandy mudstones, and tan-red mudstones." The main fossil locality is in the Jiulaopo region on the left bank of the Bahe River in Lantian.
Legacy sediment (LS) is depositional bodies of sediment inherited from the increase of human activities since the Neolithic. These include a broad range of land use and land cover changes, such as agricultural clearance, lumbering and clearance of native vegetation, mining, road building, urbanization, as well as alterations brought to river systems in the form of dams and other engineering structures meant to control and regulate natural fluvial processes (erosion, deposition, lateral migration, meandering). The concept of LS is used in geomorphology, ecology, as well as in water quality and toxicological studies.
The Omingonde Formation is an Early to Middle Triassic geologic formation, part of the Karoo Supergroup, in the western Otjozondjupa Region and northeastern Erongo Region of north-central Namibia. The formation has a maximum thickness of about 600 metres (2,000 ft) and comprises sandstones, shales, siltstones and conglomerates, was deposited in a fluvial environment, alternating between a meandering and braided river setting.
The Aksu Basin is a sedimentary basin in southwestern Turkey, around the present-day Aksu River. Located at the intersection of several major tectonic systems, in the Isparta Angle, the Aksu Basin covers an area of some 2000 square kilometers. Together with the Köprü Çay Basin and the Manavgat Basin, the Aksu Basin forms part of the broader Antalya Basin. It forms a graben relative to the surrounding Anatolian plateau.
