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| A form of mechanical weathering that occurs when loose fragments or particles of rocks and minerals that are being transported, as by water or air, collide with each other or scrape the surfaces of stationary rocks. |
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| A triangular deposit of sediment left by a stream that has lost velocity upon entering a broad, relatively flat valley. |
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| The lower limit of erosion by a stream. Sea level is the ultimate base level. However, lakes can serve as a temporary base level in upstream areas. |
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| The larger, heavier particles that are being transported by a stream. Instead of being dissolved or suspended, these are being rolled or bounced along, spending at least part of their time in contact with the stream bottom. See also: load, suspended load, dissolved load. |
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| A deposit of sediment that forms where a stream enters a standing body of water such as a lake or ocean. The name is derived from the Greek letter "delta" because these deposits typically have a triangular shape in map view. |
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| The volume of water in a flowing stream that passes a given location in a unit of time. Frequently expressed in cubic feet per second or cubic meters per second. Calculated by the formula Q = A x V where Q is the discharge, A is the cross sectional area of the channel and V is the average velocity of the stream. |
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| A ridge that separates two adjacent drainage basins. |
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drainage basin or watershed [image] |
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| The geographic area that contributes runoff to a stream. It can be outlined on a topographic map by tracing the points of highest elevation (usually ridge crests) between two adjacent stream valleys. The watershed of a large river usually contains the watersheds of many smaller streams. Also referred to as a "drainage basin". |
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| A flood that occurs within a few hours (usually less than six) of heavy or excessive rainfall, dam or levee failure. |
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| An area of alluvium-covered, relatively level land along the banks of a stream that is covered with water when the stream leaves its channel during a time of high flow. |
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| deep ditch cut by running water (especially after a prolonged downpour) |
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| In hydrologic terms, erosion which occurs in the upstream end of the valley of a stream, causing it to lengthen its course in such a direction. |
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| A protective barrier built along the banks of a stream to prevent flooding. See also natural levee. |
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| are looping changes of direction of a stream. These may be somewhat sine-wave in form. Typically, over time, the meanders don't disappear but ... |
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| A crescent-shaped lake that forms when a meandering stream changes course. Such changes in course frequently occur during flood events when overbank waters erode a new channel. |
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| A cylindrical or hemispherical hold in the bedrock of a stream that is formed from the continual swirling motion of sand and gravel by swirling currents. |
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| A chemical weathering process in which a material is dissolved. Also, the transport of dissolved ions by the water of a stream. |
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| A level plain lying above and running parallel to a stream bed. A stream terrace is formed when a stream's bed erodes to a substantially lower level, leaving its floodplain high above it. |
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| An opening in a resistant ridge where a trunk river has cut through the ridge. |
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