Geography Chapter 15, River Systems

Rivers have what characteristics (5)

- Natural agent of mass denudation - Essential water supply - Receive, dilute and transport wastes - Provide cooling water for industries - Form transportation networks

drainage divide

-Ridges that divide the runoff occurring in a watershed draining to a same river. -A geographical barrier, such as a ridge, hill, or mountain, that separates different watersheds

Three types of load in streams:

1. Dissolved load (solution): chemical solution 2. Suspended load: fine-grained particles 3. Bed load: coarser materials

steps of a formation of an oxbow lake

1. a narrow neck is formed where a lengthening meander loop back on itself 2.the neck narrow even more due to undercutting of its banks 3. the stream erodes around the neck, forming a cutoff 4.an oxbow lake forms as sediment fills the area between the new stream channel and its old meander

oxbow lake

A crescent-shaped lake (often temporary) that is formed when a meander of a river is cut off from the main channel

Rectangular Drainage

A flow pattern in which streams consist mainly of straight line segments with right angle bends and tributaries join larger streams at right angles. A rectangular pattern is formed by a faulted and jointed landscape, which directs stream courses in patterns of right-angle turns.

stream hydrograph

A graph of stream discharge over time for a specific place is called a

gully

A large channel in soil formed by erosion. A large channel in soil that carries runoff after a rainstorm

Parallel Drainage

A parallel drainage is associated with steep slopes. where the geology is sedimentary rock fault lines may create a drainage pattern where streams flow parallel to each other.

Radial Drainage

A radial drainage pattern results when streams flow off a central peak of dome. A flow pattern where streams flow outward and downward from a central elevated point.

rill

A tiny groove in soil made by flowing water

nickpoints

An incised head cut within a stream bed and indicates a sudden lowering of stream bed level

undercut bank erosion

Areas of maximum stream velocity have more power to erode, so they undercut the stream's banks on the outside of a bend

How do continental divides relate to drainage basins

Continental divides separate drainage basins and send flows to the Pacific, the Gulf of Mexico, the Atlantic, Hudson Bay, or the Arctic Ocean.

River delta

Delta is the level or nearly level depositional plain that forms at the mouth of a river A land-form that forms at the mouth of a river, where the river flows into an ocean, sea, etc; form from deposition of sediment carried by a river as the flow leaves its mouth.

Desert climates have

Desert - very low drainage density.

stream discharge

Discharge is the streamflow volume passing a point in a given unit of time Volume of water that flows past a specific point per unit of time

erosion

Erosion: grain particles (sediment) eroded from the riverbed.

floodplain

Floodplain is the area that is inundated when the river overflows its channel during times of high flow.

if flow in an internal drainage basin does not reach the ocean, what are its only two outlets

Flow in an internal drainage basin does not reach the ocean, the only outlets being evaporation and subsurface gravitational flow.

floodplains, alluvial fans, alluvial terraces, and river deltas.

Fluvial depositional landforms include floodplains, alluvial fans, alluvial terraces, and river deltas.

humid climates have

Humid climate - high drainage density

Deranged Drainage

In formerly glaciated regions, there may not have been time for an organized drainage pattern to develop and the streams can flow in many directions and there may be many lakes in the area. • Deranged drainage patterns are often in the areas with disrupted surface patterns, such as the glaciated shield regions of Canada. • A deranged pattern is associated with no clear geometry and no true stream valley pattern.

point bar deposition

On a bend's inner side, stream-velocity decreases, leading to deposition of sediment and forming a point bar

Drainage Basin (watershed)

Portion of land that contributes water to a river or waterway.

how is discharge calculated

Q = w × d × v

types of Single-thread channels

Straight rivers: (mountain rivers) tend to occur in head water areas where gradient is high. Meandearing rivers: are more common in lower-gradient areas with finer sediments

what is the basic fluvial system?

The basic fluvial system is a drainage basin, or watershed.

drainage pattern

The drainage pattern is the arrangement of channels in an area, which is influenced by climatic and geologic conditions. can be low, med, or high drainage patterns

alluvium

The general term for the unconsolidated clay, silt, sand, gravel, and mineral fragments deposited by running water.

gradient of a stream

The gradient of a stream is defined as the drop in elevation per unit distance. The river has a steeper slope nearer the headwaters and a more gradual slope downstream.

base level

The lowest point to which a stream can erode The level below which a stream cannot erode its valley is base level.

The mouth of a river is where

The mouth of a river is where the river reaches the ocean

fluvial transport

The moving of sediments and dissolved materials as a result of water flow within (and at times beyond) a stream channel

The ongoing interaction between erosion, transportation, and deposition in a river system produces

The ongoing interaction between erosion, transportation, and deposition in a river system produces fluvial landscapes.

internal drainage basin or endorheic systems.

The water leaves the drainage basin by means of evaporation or subsurface gravitational flow

sheetflow

The water that moves downslope in a thin film as overland flow, not concentrated in channels larger than rills.

Alluvial fans occur where

They commonly occur at the mouth of a canyon where an ephemeral stream channel exits.

deposition

This material is then transported and deposited in new locations.

Three types of sediment load are

Three types of sediment load are dissolved load, suspended load, and bed load.

Units of discharge:

Units of discharge: Cubic Length/Time (e.g., m3/s, cfs(cubic feet per second)).

Some streams do not reach the ocean. what happens to this water

Water leaves the basin through evaporation or subsurface gravitational flow. (or endorheic systems.)

How do drainage basins form?

When it rains, runoff can form as sheet flow and then concentrate in rills (small grooves), gullies and stream channels

With excess sediment, a stream may become a

With excess sediment, a stream may become a maze of interconnected channels that form a braided stream pattern.

Dendritic Drainage

a drainage pattern for rivers that looks like a tree, with progressively bigger rivers, all ending into one large river at the bottom. Energy expanded by this drainage system is efficient because the overall length of the branches is minimized.

Depositional Landforms

alluvium

Alluvial fans

are prominent cone-shaped fluvial deposits.Alluvial fans

channel patterns

braided rivers, single thread channels

The processes of fluvial deposition occur when a stream deposits alluvium, thereby creating

depositional landforms, such as bars, floodplains, terraces, and deltas.

Trellis Drainage

drainage pattern in which most of the streams occupy parallel valleys, pattern usually develops on folded strata of rocks with differing resistance to erosion The trellis drainage pattern is characteristic of dipping or folded topography. • Such drainage exists in the nearly parallel mountain folds of the Ridge and Valley Province in the eastern United States (e.g., Tennessee).

Finer materials, such as silty mud and clays, are carried___________ and form ____________.

farther and form the extreme end of the deposit

meandering stream

fluvial landform where the channel swings, curves migrate downstream, erodes outside bank (fast), deposits on inside bank (slow), increasing sinuosity A river or small stream that curves back and forth across its valley

Two main driving forces of fluvial systems:

insolation and gravity

Where the slope is gradual, stream channels develop a sinuous form called a

meandering stream

where is stream energy concentrated

nickpoints produced by resistant rock strata, accelerated erosion

Fluvial

of, relating to, or living in a stream or river(flowing, alluvial)

braided rivers

tend to occur in areas with abundant sediment or in the lowest reaches of large river systems. is featured by excess of sediment and interconnected channels that form a pattern. • Multiple large channels are present across a vast floodplain.

Most streams flow into

the ocean.

Streams create fluvial landscapes through

the ongoing erosion, transport, and deposition of materials in a downstream direction

drainage density

the summed length of all stream channels per unit area in a drainage basin; the total length of all channels in a drainage basin divided by its drainage area; indicates how dissected the landscape is by channels, it reflects both the tendency of the drainage basin to generate surface runoff and the erodibility of the surface materials

drainage density equation

total length of all stream channels in the basin/area of the basin

stream transport

transportation of particles by Solution,Suspension,Saltation, Traction

how does urbanization effect on a stream hydrograph

urbanization can increase peak flow and shorten lag time between storm peak and stream discharge peak.

Annular Drainage

• A pattern of stream flow in which the stream tends to form a circular path around the hill. • It happens when there is a layer of less resistant rock in the hill.

characteristics of alluvial fans

• Alluvial fans are produced when flowing water abruptly loses velocity as it leaves the constricted channel of a canyon. • Water flows over the surface of the fan and produces a pattern shifting from channel to channel.

Seven Common Drainage Patterns

• Dendritic drainage • Trellis drainage • Radial drainage • Parallel drainage • Rectangular drainage • Annular drainage