Alluvium in the context of "Salton Sea"

A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it runs out of water, or only flow during certain seasons. Rivers are regulated by the water cycle, the processes by which water moves around the Earth. Water first enters rivers through precipitation, whether from rainfall, the runoff of water down a slope, the melting of glaciers or snow, or seepage from aquifers beneath the surface of the Earth.

Rivers flow in channeled watercourses and merge in confluences to form drainage basins, areas where surface water eventually flows to a common outlet. Drainage divides keep rivers separated from other courses of water and causes upstream water within the confines of the divide to fall into the downhill stream. Rivers have a great effect on the landscape around them. They may regularly overflow their banks and flood the surrounding area, spreading nutrients to the surrounding area. Sediment or alluvium carried by rivers shapes the landscape around it, forming deltas and islands where the flow slows down. Rivers rarely run in a straight line, instead, they bend or meander; the locations of a river's banks can change frequently. Rivers get their alluvium from erosion, which carves rock into canyons and valleys.

An alluvial plain is a plain (an essentially flat landform) created by the deposition of sediment over a long period 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 time. In contrast, the alluvial plain is the larger area representing the region over which the floodplains have shifted over geological time.

As the highlands erode due to weathering and water flow, the sediment from the hills is transported to the lower plain. Various creeks will carry the water further to a river, lake, bay, or ocean. As the sediments are deposited during flood conditions in the floodplain of a creek, the elevation of the floodplain will be raised. As this reduces the channel floodwater capacity, the creek will, over time, seek new, lower paths, forming a meander (a curved path). The leftover higher locations, typically natural levees at the margins of the flood channel, will be eroded by lateral stream erosion, local rainfall, and possibly wind transport if the climate is arid and does not support soil-holding grasses. These processes, over geologic time, will form the plain, a region with little relief (local changes in elevation) yet with a constant but slight slope.

The prehistory of Mesopotamia is the period between the Paleolithic and the emergence of writing in the area of the Fertile Crescent around the Tigris and Euphrates rivers, as well as surrounding areas such as the Zagros foothills, southeastern Anatolia, and northwestern Syria.

In general, Paleolithic Mesopotamia is poorly documented, with the situation worsening in southern Mesopotamia for periods prior to the 4th millennium BC. Geological conditions meant that most of the remains were buried under a thick layer of alluvium or submerged beneath the waters of the Persian Gulf. The Middle Paleolithic witnessed the emergence of a population of hunter-gatherers who lived in the caves of the Zagros and, seasonally, in numerous open-air sites. They were producers of a lithic industry of the Mousterian type, and their funerary remains, found in the cave of Shanidar, indicate the existence of solidarity and the practice of healing between the members of a group. During the Upper Paleolithic, the Zagros was probably occupied by modern man. The Shanidar cave contains only tools made of bone or antler, typical of a local Aurignacian called "Baradostian" by specialists.

The Ubaid period (c. 5500–3700 BC) is a prehistoric period of Mesopotamia. The name derives from Tell al-'Ubaid where the earliest large excavation of Ubaid period material was conducted initially in 1919 by Henry Hall, Leonard Woolley in 1922–1923, and later by Pinhas Delougaz in 1937. Excavations continue into the present day.

In Southern Mesopotamia, this period marks the earliest known human settlements on the alluvial plain, although it is likely earlier periods exist that are obscured under the alluvium. In the south it has a very long duration between about 5500 and 3800 BC when it is replaced by the Uruk period.

In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish word placer, meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, aeolian placers and paleo-placers.

Placer materials must be both dense and resistant to weathering processes. To accumulate in placers, mineral particles must have a specific gravity above 2.58.

A levee (/ˈlɛvi/ or /ˈlɛveɪ/), dike (American English), dyke (Commonwealth English), embankment, floodbank, or stop bank is an elevated ridge, natural or artificial, alongside the banks of a river, often intended to protect against flooding of the area adjoining the river. It is usually earthen and often runs parallel to the course of a river in its floodplain or along low-lying coastlines.

Naturally occurring levees form on river floodplains following flooding. Sediment and alluvium are deposited on the banks and settle, forming a ridge that increases the river channel's capacity. Alternatively, levees can be artificially constructed from fill, designed to regulate water levels. In some circumstances, artificial levees can be environmentally damaging.

Narta Lagoon (Albanian: Laguna e Nartës) is a lagoon of the Adriatic Sea on the Mediterranean Sea in the central coast of Albania. The lagoon extends north of the Bay of Vlorë on the eastern shore of the Strait of Otranto and is separated from the sea by a narrow littoral strip, consisting of an alluvial dune. It has a surface area of 41.8 km (16.1 sq mi) with a maximal depth of 1.5 m (4.9 ft).

It is situated within the boundaries of the Vjosa Wild River National Park, and has been recognised as an important Bird and Plant Area of international importance. As of May 2020, it is home to 3,000 flamingos. It is formed by the constant accumulation of solid flow of the Vjosa River, which originates within the Pindus Mountains close to the border between Albania and Greece.