STREAMS

hydrology or geo-hydrology is the study of streams or groundwater Basic nature of steams Definition, origin and course of stream definition and explanation a flowing body of water mostly contained in a channel at Earth’s surface running water is a powerful agent of erosion and principal sculpture of Earth’s landscape. perennial streams flow year round and intermittent (ephemeral) streams do not.

STREAMS origin hydrologic cycleprime source of stream water is from runoff from the hydrologic cycle fate of precipitation = runoff (into streams, ponds and lakes) + infiltration ( into subsurface—groundwater) + evaporation + transpiration ( used by plants)

STREAMS stream course and retention of water in channel path of stream can depend on: slope of land geologic structures as folds, fractures and faults rock hardness retention of water in channel depends largely on the presence and degree of channel coating by clay, silt or other impermeable substances

STREAMS Stream system tributaries smaller streams which collect and supply materials and water to the main stream main stream or main trunk the main stream which receives materials and water from the tributaries and is the prime transporter of materials in the stream system

STREAMS Stream profile and related terms stream profile head mouth examples of mouth are juncture of stream with: another stream; a pond or lake; the ocean decreasing gradient of channel downstream slope of stream channel is greatest at head and smallest at mouth

Stream profile STREAMS Stream water flows faster if the gradient is higher and erodes mostly downward, while slower with lesser gradient, and water can start eroding sideways resulting in channel meander Land uplift results in faster flow and higher downward erosion trunk many tributaries

STREAMS base level lowest level to which a stream can erode its channel local or temporary base levels include lakes, resistant rock formation(s) and streams which act as base level for their tributaries-- ultimate base level is sea level head-ward erosion and stream piracy head ward erosion is the extension of a channel head ward up the slope of erosion stream piracy is the diversion of waters of one stream by another stream and head ward erosion of pirating stream

STREAMS Stream piracy and changing channel direction can cause large problems at local, state--national and international levels

STREAMS capture or piracy of water from stream A by stream B can cause a problem.

STREAMS Stream water velocity governs both erosion and deposition rates--magnitude of erosion is proportionate to stream velocity and that for deposition is inversely proportionate to velocity some factors affecting stream velocity: shape of stream channel a deep narrow or wide shallow channel retard total water velocity a semicircular channel allows faster moving water based on area of friction

Channel shape and stream velocity

STREAMS roughness of channel rough channel with boulders and large rocks causes a decrease of water velocity stream gradient is a measure of the slope of the channel expressed as the number of feet dropped per mile as measured between 2 points along the path of the stream

STREAMS change in channel area along the stream if channel area increases downstream, water velocity decreases alluvial fans or deltas form when depositional rates of materials increase as velocity of water decreases--these features will be discussed in detail later Stream loads materials carried by stream waters stream competency refers to the maximum size particle(see Wentworth’s scale) a stream can transport

STREAMS suspended load suspended particles in stream waters usually includes clay and silt sizes most streams carry largest part of their load in suspension bed load particles which bounce or skip (saltation) while being transported by the stream for most streams sand size particles dissolved or solution load stream velocity has no influence on this-- precipitation occurs based on water chem.

STREAMS Stream and drainage patterns, drainage basins and divides Stream patterns are in reference to shape of individual stream channel straight channel often present near headwaters where erosion is downward into the channel meander channel snakelike in shape and present downstream from the head--these are significant near the mouth

STREAMS braided channel stream channel which intertwines caused if slope or discharge of stream decreases

STREAMS braided channel straight channel meandering channel

STREAMS meandering channel braided channels Photos of meandering and braided channels

STREAMS Drainage patterns are in reference to a stream and its tributaries dendritic or arborescent resembles veins of a tree leaf and is the most abundant type of drainage pattern

STREAMS radial streams diverge from a central area like spokes from the hub of a wheel develops on volcanic cones or domal uplifts

STREAMS rectangular comprised of many right angle bends develops in bedrock crisscrossed by a series of joints and/or faults which represent precut channels in which water can flow

STREAMS trellis a rectangular type of pattern in which tributary streams are nearly parallel to each other and look like a garden trellis forms on folded rocks resulting in alternating parallel bands of resistant and less resistant rock like in the Appalachian Mountains

STREAMS Drainage basin and divide a drainage basin is the total land area that contributes water and material to a stream a divide is an elevated area which separates drainage basins and range in size from a ridge separating small gullies to continental divides which split continents into large drainage basins

Drainage basins and divides STREAMS

Mississippi River Basin and Divides STREAMS

Stream features and channelization Meander and oxbow stream velocity is greatest on outside of meander causing a cut bank and slowest on inside resulting in point bars—meandering starts to form when a slight difference in roughness on channel bottom occurs the water molecules in a stream moving around a bend align like a line of ice skaters in which the outside skaters are moving much faster then those in the inside

Cut-bank, point bar and water velocities STREAMS

as the outside portion of the meander continues to erode the neck of land between, the outer portions become narrowed to the extent which isolates or “cuts off “ the loop called an oxbow typically this horseshoe shaped feature is a lake initially but with time will become a oxbow scar as the lake fills with sediment typically oxbow scars are located a longer distance from the river than oxbow lakes

Formation of an oxbow STREAMS

Meanders can show a curved pattern of development forming an oxbow Development of meander

Oxbow Lakes

Meander scars STREAMS An older stage of stream meander development

STREAMS --an Entrenched (Encised) meander is a deepened meander channel caused by subsequent rejuvenation (uplift) of the channel--

STREAMS Entrenched (Encised) Meander in Colorado River in the Grand Canyon

STREAMS Alluvial fan and delta as the water leaves it's channel and spreads, the water moves slower and material is deposited this is apparent at the base of mountains as water enters valleys and at the mouth of large streams as they enter the oceans the results of this deposition forms alluvial fans and deltas

Alluvial fan at the base of a mountain

Deltas formed at mouth of streams discharging materials entering the ocean STREAMS

Floodplain and natural levee a floodplain is a relatively flat region flanking large streams and formed by deposition of finer sediments during periodic flooding a natural levee is a ridge or platform built on the floodplain adjacent to and trending along the course of the stream and represents the highest area or point on a floodplain levees are caused during flooding and can inhibit subsequent flooding

STREAMS formation of a levee during flooding water velocity is slower and material accumulates in long mounds as flooding recedes, mounds are exposed.

Floodplain and natural levees STREAMS

Floodplain STREAMS

Natural levee with stream water breakthrough STREAMS

Channelization structural alteration made to the channel of a stream in order to speed flow of water and thus prevent flooding usually involves cutting off a meander to straighten the course of a stream the resultant shorter straight channel is made to have a steeper gradient and the increased steam water velocity will transport more water possibly enough to prevent flooding in an area

STREAMS

Stream Channelization

STREAMS Stream Channelization

RiverCountry Average Discharge at Mouth (Thousands of cubic feet per second) AmazonBrazil7,500 Congo 1,400 YangtzeChina770 BrahmaputraBangladesh700 GangesIndia660 YeniseyRussia614 MississippiUSA611 OrinocoVenezuela600 LenaRussia547 ParanaArgentina526 WORLD'S TEN LARGEST RIVERS BY DISCHARGE Stream Discharge: Measure of the Stream volume/second at It’s Mouth (7.5 gallons/cubic foot)