GEOL - Hydrological cycle and rivers/ streams

gradient

- change in elevation as function of distance from head (source) to mouth (end of a river)

understand the hydrologic cycle- what is precipitation

- condensed water vapor in troposphere falling back to earth surface as rain or snow

longitudinal profile at the headwater of river

- gradient is STEEP -velocity is HIGH - channel roughness is high -discharge is low -channel size is low -erosion dominates (especially of larger sediments)

understand the hydrologic cycle (pic)

- this is how water moves through earths resivour

stream flow

- this is runoff and infiltration

understand the hydrologic cycle- what is evaporation

- water changing from liquid to gas (water vapor) driven by heat from sun -(water goes from ocean into atmosphere)

velocity of a stream is dependent on

-discharge -gradient

longitudinal profile at the mouth of river

-gradient FLATTENS (is lower) -channel is smoother but meanders (curves) -discharge is high -channel size is wide -transportation dominates (of a lot of fine grained sediments)

the difference between runoff and infiltration depends on

-intensity and duration of rainfall -the amount of water already in the soil -the nature of the surface material -slope of land surface -extent and type of vegetation -this is if water will either runoff the land or perclate into it (inflitration) -runoff is high in urban areas due to buildings, roads, and parking lots

atmosphere distribution of water on earth

.001%

soil moisture distribution of water on earth

.001%

lakes and rivers distribution of water on earth

.014%

groundwater distribution of water on earth

1.70%

glacial ice distribution of water on earth

1.76%

longitudinal profile at the headwater of river velocity is

High

alluvial fan

Is a change from high gradient change to low gradient change- the river is changing speed, sediment falls out and a form of sediment is formed Conical, fan shaped structures that build at the base of a mountain front Sediments drop out rapidly with a change in stream gradient The coarsest materials is found near the mouth of the canyon Sediments become fine and thin with distance How a lot of conglomerates are made

How are oxbow lakes formed?

Meanders increase until the meander is cut off Cutbanks come together and a meanders neck thins During flooding, high velocity flow saws through the neck The meander cut off forms an oxbow lake It is filled off with sediment, leaving an arc shaped scar

meander- how it forms

The river has slowed, we are encountering land that has little to no gradient change and are shallow In other words- channels can form intricately loopin curves when the land surface gradient is low

What are the typical downstream changes in velocity- what causes these changes?

Velocity is not uniform in all areas of a channel In curved channels, maximum velocity traces the outside curve The outside curve= fastest velocity - fastest at cut bar Fastest part of stream is on the outside of the curve High momentum erodes outside bank(Cut bank) Slower water deposits point bars on inner part of curve

In terms of features formed at the surface of the earth, _______ the most important agent of transportation, erisions, and deposition of weather material

WATER

flood

When a river/ stream overflows it banks During a flood.... -Discharge increase -Flow exceeds stream channel -Moving water and debris scour floodplains -Velocity slows away from the main channel and sediment drops (this forms natural levees)

Delta

When a stream enters standing water ( a lake, ocean etc) the current slows, losses competence, and sediments drop out They evolve over time- example = Mississippi river

meander in terms of velocity

With velocity.... Bends, or curves, in river/streams water velocities are lower on inside of meander ( because of deposition - point bar ) and higher on outside meander forms a flood plain

which has the least distribution of water on earth?

atmosphere AND soil moisture (both have .001%)

steep gradient =

big change in elevation and low change in distance

During what flood cycle does the river do most of its work of erosion and transport?

come back

How are point bars formed?

come back

Sediment transport two components

competence and capacity

gradient from head to mouth

decreases from head to mouth is really high at head and decreases overtime to mouth

longitudinal profile at the headwater of river does erosion or transportation occur?

erosion - especially of large sediments

atmospheric part of hydrologic cycle

evaporation precipitation condensation

longitudinal profile at the headwater of river channel roughness is

high

longitudinal profile at the mouth of river , discharge is

high

gradients therefore affects

how fast the water is moving -what type of streams form -transportation of sediments

longitudinal profile at the headwater of river channel size is

low

longitudinal profile at the headwater of river discharge is

low

longitudinal profile at the mouth of river gradient is

low (it flattens)

gentle gradient =

low change in elevation over a long change in distance

oceans distribution of water on earth

most -96.5%

know the relative distribution on the earth of

oceans glacial ice groundwater lakes and rives soil moisture atmosphere

equilibration for hydrologic cycle

over the oceans- evaporation should be more than precipitation ( oceans.... so oceans would be drying up over the lands- precipitation should be more than evaporation so the land would be flooded by water but theres equilibration

What is a longitudinal profile

plot of elevation of river from head (source) to mouth (end of river)

longitudinal profile at the mouth of river the channel is

smoother but meanders (bends)

longitudinal profile at the headwater of river gradient is

steep

Drainage basin / watershed

the area of land over which it precipitation falls, it would be drained by rivers in that basin in other words... an area of land that is connected and all the water that falls from precipitation can be traced to one stream

drainage (watershed) divide

the imaginary line separating one basin from another occurs a lot in mountainous areas

How does the longitudinal profile of a river or stream change from its headwaters to its mouth?

the longitudinal profile is different at the headwater and the mouth

which has the most distribution of water on earth?

the ocean

longitudinal profile at the mouth of river is there erosion or transportation?

transportation *usually of small sediments*

discharge

volume of water passing a point per unit time it is an amount of water passing during a time if your standing in a river how much water comes to you per min, sec etc

Understand the hydrologic cycle- what is condensation

water changing from gas to liquid -driven up by water vapor moving up in Earth's lowermost atmospheric layer (troposphere) and being cooled - clouds

understand the hydrologic cycle- surface runoff

water flowing on land surface downhill to oceans

longitudinal profile at the mouth of river , channel size

widens

Floodplain

Area over which rivers/ stream meander, can be covered during a flood A river floodplain is formed overtime by the meandering stream Are often bounded by bluffs During floods, entire floodplains may be immersed Natural levees form ridges parallel to the channel So is this just referring to the area in specific where the flood happens?

Sediment transport-

Changes because of discharge High discharge- large cobbles and boulders may move Low discharger- larger clasts are stranded

natural leeves

Raised areas next to the channel formed during a flood event ( during flood plain) Water overtops stream banks and flows out like a flat sheet Loses velocity instantly and drops coarse sediments near the banks Fine material is laid out in the valley floor Following a flood event, levees prevent water from returning to stream channels Poorly drained back swamps form in the floodplain

Capacity-

The maximum load transported The amount that can be transported in the river High capacity= high sediment load Low capacity = low sediment load You can have a high capacity and low competence etc -they are independent of each other and don't go hand and hand

compentence

The maximum size transported (of rock)

What does it mean to have an X- year flood? Where X can equal 10, 50, 100, 300

The numbers refer to years The year probability that only once in the next X-years will flood with discharge equal to or greater than , flood occur again The smaller the number, the more likely it occurs 2 year flood, there's a 50% chance it happens any given year Flood risks are calculated as yearly probabilities X year floods are called the recurrence interval The recurrence interval is the average of years between floods of a particular size 100 year flood, there is a 1 in 100 = 1% probability We look at increase of discharge and how often that will occur Big floods = less likely, little floods =more likely