Stream Processes Quiz

Continental Divide

A narrow strip of land dividing surface waters that drain in opposite directions across the continent. The continental divide in North America is an imaginary line along the crest of the Rocky Mountains. Rainwater that falls east of the line drains eastward into the Atlantic Ocean, and rainwater that falls west of the line drains westward into the Pacific Ocean. Therefore, North America's this is sometimes called "The Great Divide."

Rectangular Pattern

A network of channels with right-angle bends that form a pattern of interconnected rectangles and squares. This pattern often develops over rocks that are fractured or faulted in two main directions are perpendicular (at nearly right angles) and break the bedrock into THIS or square blocks. The streams erode channels along the perpendicular fractures and faults.

Trellis Pattern

A pattern of channels resembling a vine growing on this structure. Develops where tilted layers of resistant and nonresistant rock form parallel ridges and valleys. The main stream channel cuts through the ridges, and the main tributaries flow along the valleys parallel to the ridges and at the right angles to the main stream.

Deranged Pattern

A random pattern of stream channels that seem to have no relationship to underlying rock types or geologic structures.

Annular Pattern

A set of incomplete, concentric rings of streams connected by short radial channels. This pattern commonly develops on eroding structural domes and folds that contain alternating folded layers of resistant and nonresistant rock types.

Alluvial Fan

A similar fan-shaped deposit of stream sediment also occurs where a steep-gradient stream abruptly enters a wide, level plain, creating this.

Flood

All streams--prennial and intermittent--have the potential to do this or overflow their banks. This natural function damages more human property in the U.S. than any other natural hazard.

Fluvial Processes

Another name for stream processes. They are among the most important agents that shape Earth's surface and cause damage to humans and their property.

Groundwater

As water drenches the landscape, some soaks into the ground and becomes this.

Headward Erosion

At the head of a stream, the stream channels deepen and erode their V-shaped channels uphill though time. The worn-away sediment is transported downstream by tributaries.

Radial Pattern

Channel flow outward from a central area, resembling the spokes of a well. Water drains from the inside of the pattern, where the "spokes" nearly meet, to the outside of the pattern (where the "spokes are farthest apart)> This pattern develops on conical hills, such as volcanoes and some structural domes.

Centripetal Pattern

Channels converge on a central point, often a lake or playa (dry lake bed), at the center of a closed basin (a basin from which surface water cannot drain because there is no outlet valley).

Centripetal Pattern

Channels converge on the lowest point in a closed basin from which water cannot drain.

Deranged Pattern

Channels flow randomly with no relation to underlying rock types or structures.

Rectangular Pattern

Channels have right-angle bends developed along perpendicular sets of rock fracture joints.

Oxbow Lake

Channels may cut new paths during floods. This can cut off the outer edge of a meander, abandoning it to become crescent-shaped.

Radial Pattern

Channels radiate outward like spokes of a wheel from a high point.

Point Bar

Deposits of mostly gravel and sand that accumulate along the inner edge of meanders.

Floodplains

Develop when alluvium accumulates landward of the river banks, during floods. However, most flooding events do not submerge this entire area.

Sheet Flow

During drenching rainstorms, some of the water spas slowly into the ground. But most of the water flows over the ground before it can seep in. It flows over the ground sidewalks as sheets of water several millimeters or centimeters deep. It is called this. This BLANK moves downslope in response to the pull of gravity, so that the water flow from streets and sidewalks to ditches and street gutters.

Cutbanks

Erosion occurs on the outer edge of the meanders.

Levees

Flooding creates these, which are higher than the rest of the floodplain.

Perennial Streams

Flow continuously throughout the year and are represented on topography maps as blue lines.

Intermittent Streams

Flow only at certain times of the year, such as rainy seasons or when snow melts in the spring. They are represented on topogrpahic maps as blue line segments separated by blue dots (three blue dots between each line segment).

Base Flow

Groundwater that steeps into a stream via porous rocks, fractures, and springs.

Yazoo Tributary

If a tributary cannot breach a river's levees, then it will become this, which flows parallel to the river.

Playa

If the river water enters a dry basin at the mouth of the river, it will evaporate and precipitate layers of mineral crystals and oxide residues in this.

Head

In the uplands, this is the stream's (tributary's) point of origin, and may be at a spring or at the start of narrow runoff channels during rainstorms.

Dendritic Pattern

Irregular pattern of channels that branch like a tree. Develops on flat lying or homogeneous rock.

Channel Bars

Linear, underwater sandbars

Annular Pattern

Long channels form a pattern of concentric circles connected by short radial channels. Develops on eroded domes or folds with resistant and non-resistent rock types.

Deposition

Occurs if the velocity of the stream drops (allowing sediments to settle out of the water) or if parts of the stream evaporate (allowing mineral crystals and oxide residues to form).

Transportation

Occurs when weathered materials are drafted, bounced, and carried down-stream (as suspended grains or chemicals in the water).

Weathering

Occurs where the stream physically erodes and disintegrates Earth materials and where it chemically decomposes or dissolves Earth materials to form sediment and aqueous chemical solutions.

Trellis Pattern

Resembles a vine or climbing rose bush growing on this structure, where the main stream is long and intersected at nearly right angles by its tributaries. This pattern commonly develops where alternating layers of resistant and nonresistant rocks have been tilted and eroded to form a series of parallel ridges and valleys. The main stream channel cuts through the ridges, and the main tributaries flow perpendicular to the main stream and along they valleys (parallel to and between the ridges).

Dendritic Pattern

Resembles the branching of a tree. Water flow is from the branch-like tributaries to the trunk-like main stream or river. This patter is common where a stream cuts into flat lying layers of rock or sediment. It also develops where a stream cuts into homogeneous rock (crystalline igneous rock) or sediment (sand).

Differential Erosion

Rocks comprised of hard, chemically resistant minerals are generally more resistant to erosion and form ridges or other hilltops. Rocks comprised of soft and more easily weathered minerals are generally less resistant to erosion and form valleys.

Stream Terraces

Some stream valleys have level surfaces that are higher than the present floodplain. These are remnants of older floodplains that have been dissected (cut by younger streams).

Meandering

Still farther downstream, the gradient decreases even more as discharge and load increase. The stream valleys develop very wide, flat floodplains with sinus channels. These channels may become highly sinuous or THIS. They migrate over time as progressive erosion of cutbacks and point bars takes place over times.

Land Erosion

Streams are the single most important natural agent of this, which is the wearing away of the land. They wear away more sediment from land than wind, glaciers, or ocean waves.

Load

The amount of material (mostly alluvium, but also plants, trash, and dissolved material) that is transported by a stream. In the uplands, most streams have relatively steep gradients, so the streams are cut narrow, V-shaped valleys. Near their heads, tributaries are quick to transport their load downstream, where it combines with the loads of other tributaries. THIS is transferred to the larger streams and, eventually, to the main river. THIS is eventually deposited at the mouth of the river, where it enters a lake, ocean, or dry basin.

Geology

The bedrock this over which the stream flows affects the stream's ability to find or erode its course.

Mouth

The end of the river valley is at this spot on the river, where it enters a lake, ocean, or dry basin. At this location, the river water is dispersed into a wiser area, its velocity decrease, and sediment settles out of suspension to form an alluvial deposit (an alluvial fan or delta).

Drainage Basin

The entire area of land that is drained by one stream, or an entire stream drainage system.

Stream Drainage System

The entire drainage network, from the smallest upland tributaries to larger streams, to the largest river (main stream or main river), is called this.

Main Stream or Main River

The largest unit in a stream drainage system.

Divides

The linear boundaries that separate one drainage basin from another. While some divides are easy to recognize on maps, those in regions of lower relief or rolling hills have these areas that departure gentle slopes and are more difficult to map. For this reason, this area cannot always be mapped as distinct lines. It must, instead, be represented as dashed lines that signify the most probable locations.

Base Level

The lowest level to which a stream can theoretically erode. This is achieved where a stream enters a lake or an ocean. At that point, the erosional (cutting) power of the stream is zero and the depositional (sediment accumulation) processes occur.

Discharge

The rate of stream flow at a given time and location. It is measured in water volume per unit of time, commonly cubic feet per second.

Alluvium

The sediment is transported and eventually deposited and is, thus, called this. It consists of gravel, sand, silt, and clay deposited into floodplains, point bars, channel bars, deltas, and BLANK fans.

Smallest Upland Tributaries

The smallest unit in a stream drainage system.

Uplands

The smallest valleys in a drainage basin occur at its highest elevations, called this.

Gradient

The steepness of a slope--either the slope of a valley wall or the slope of a stream along a selected length (segment) of its channel. This is usually expressed in feet per mile and is determined by dividing the vertical rise or fall between two points on the slope (in feet) by the horizontal distance (run) between them (in miles).

Delta

The stream drops its sediment load, which accumulates as a triangular or fan-shaped deposit. In a lake or ocean, such a deposit is called this.

Erosion

The wearing away of rock and sediment is the dominant process at the head of a stream.

Braided Stream

When low gradient/high discharge streams become overloaded with sediment, they may form these. They consists of braided channels with linear, underwater sandbars (channel bars) and islands.