WeatheringWeathering Leads to sediment sourceLeads to sediment source Rocks must be broken down into smaller Rocks must be broken down into smaller

componentscomponents Sediment generated from rocks termed clastic sedimentSediment generated from rocks termed clastic sediment

Clastic refers to fragments of rocksClastic refers to fragments of rocks

Sediment generated transported to oceansSediment generated transported to oceans Coarser sediment forms beaches or other depostional Coarser sediment forms beaches or other depostional

featuresfeatures DeltasDeltas Or transported to deep oceanOr transported to deep ocean Fine grained sediment transported to shelf, slope, deep Fine grained sediment transported to shelf, slope, deep

oceanocean

Weathering•Weathering: the disintegration, or Weathering: the disintegration, or breakdown of rock materialbreakdown of rock material

2 Types of Weathering2 Types of Weathering Mechanical WeatheringMechanical Weathering: :

no change in chemical no change in chemical composition--just composition--just disintegration into smaller disintegration into smaller piecespieces

Chemical WeatheringChemical Weathering: : breakdown as a result of breakdown as a result of chemical reactionschemical reactions

Mechanical WeatheringMechanical Weathering

Physical breakup• pressure release• water: freeze - thaw cycles• crystallization of salt in cracks• thermal expansion and contraction

All this increases the total surface area exposed to weathering processes.

Mechanical WeatheringMechanical Weathering

Exfoliation:Rock breaks apart in layers that are

parallel to the earth's surface; as rock is uncovered, it expands (due to the lower confining pressure) resulting in exfoliation.

WeatheringWeatheringMechanical WeatheringMechanical Weathering

Sheet JointsSheet Joints(Exfoliation)(Exfoliation)

Stone Mountain, GA

Half Dome, Yosemite, CA

Exfoliated Domes, YosemiteExfoliated Domes, Yosemite

Stone Mountain, GA

Stone Mountain, Georgia, showing the product of exfoliation due to unloading

Frost WedgingFrost Wedging: rock breakdown : rock breakdown caused by expansion of ice in caused by expansion of ice in cracks and jointscracks and joints

Shattered rocks are Shattered rocks are common in cold and common in cold and alpine environments alpine environments where repeated freeze-where repeated freeze-thaw cycles gradually pry thaw cycles gradually pry rocks apart.rocks apart.

WeatheringWeatheringThermal expansion due to the extreme range of temperatures Thermal expansion due to the extreme range of temperatures can shatter rocks in desert environments.can shatter rocks in desert environments.

Repeated swelling and shrinking of minerals with different Repeated swelling and shrinking of minerals with different expansion rates will also shatter rocks.expansion rates will also shatter rocks.

Role of Physical WeatheringRole of Physical Weathering

1)1) Reduces rock material to smaller Reduces rock material to smaller fragments that are easier to fragments that are easier to transporttransport

2) 2) Increases the exposed surface area Increases the exposed surface area of rock, making it more vulnerable of rock, making it more vulnerable to further physical and chemical to further physical and chemical weathering weathering

Chemical WeatheringChemical Weathering

Definition: transformation/decomposition of one mineral into another

Mineral breakdown• carbonate dissolves• primary minerals --> secondary minerals (mostly clays)

Net loss of elements retained in the soil.

Dissolution

H2O + CO2 + CaCO3 --> Ca+2 + 2HCO3-

water + carbon dioxide + calcite dissolve into calcium ion and bicarbonate ion

Biological activity in soilsgenerates substantial CO2

Bicarbonate is the dominant ion in surface runoff.

ErosionErosion

Sediments produced by weathering Sediments produced by weathering are then removed by erosionare then removed by erosion

Erosion - the incorporation and Erosion - the incorporation and transportation of weathering transportation of weathering products by a mobile agent such as products by a mobile agent such as wind, water, ice.wind, water, ice.

RiversRivers IntroductionIntroduction

• • Rivers and streams are Rivers and streams are dynamic systems that dynamic systems that continually adjust to continually adjust to natural and human-natural and human-caused changescaused changes

• • Running water is the Running water is the most important geologic most important geologic agent modifying Earth’s agent modifying Earth’s land surface and is a land surface and is a source of fresh water for source of fresh water for industry, agriculture, industry, agriculture, and domestic useand domestic use

• • Management of erosion Management of erosion and flooding requires and flooding requires considerable effort and considerable effort and costcost

Salinas River, CA

http://www.co.monterey.ca.us/OES/floods_files/Salinas_River_Floods.jpg

Hydrologic CycleHydrologic Cycle

• • Water is cycledWater is cycledfrom oceans, through from oceans, through atmosphere, to atmosphere, to continents, and back to continents, and back to the oceansthe oceans• • Powered by solarPowered by solarradiation and occursradiation and occursbecause water changesbecause water changesreadily from liquid toreadily from liquid toa gas on surfacea gas on surfaceEvaporation, Evaporation, condensation, condensation, precipitation, and runoffprecipitation, and runoffcharacterize the characterize the movement ofmovement ofwater, though some is water, though some is storedstoredin lakes, groundwater, in lakes, groundwater, and iceand ice

Moving WaterMoving Water

Sheet FlowSheet Flow water moves in a water moves in a

continuous sheet continuous sheet of shallow of shallow watermoving over watermoving over the surfacethe surface

Channel FlowChannel Flow water is confined water is confined

to long trough-to long trough-like depressionslike depressions

www.duluthstreams.org/.../ impact_impervious.html

Sheet flow

LA River Channelhttp://upload.wikimedia.org/wikipedia/commons/0/07/Los_Angeles_River_Glendale.jpg

A Drainage BasinA Drainage Basin

A drainage basin is A drainage basin is extent of land where extent of land where water from rain and water from rain and melting snow or ice melting snow or ice drains downhill into a drains downhill into a body of water, such as body of water, such as a river, lake, reservoir, a river, lake, reservoir, estuary, wetland, sea or estuary, wetland, sea or ocean. The drainage ocean. The drainage basin includes both the basin includes both the streams and rivers that streams and rivers that convey the water as convey the water as well as the land well as the land surfaces from which surfaces from which water drains into those water drains into those channelschannels

Drainage Drainage Basins-Southern Basins-Southern

CaliforniaCalifornia

http://www.urbanedpartnership.org/target/units/river/drainage_map.gif

OC Public Works

Important River Important River ParametersParameters

Gradient, Velocity, Gradient, Velocity, and Dischargeand Discharge Gradient is the Gradient is the

average slope of the average slope of the channel bedchannel bed

Velocity is the Velocity is the distance water travels distance water travels in a given amount of in a given amount of timetime

Discharge is the Discharge is the volume of water volume of water passing a point in a passing a point in a given amount of timegiven amount of time

Ability to transport Ability to transport sediment depends on sediment depends on velocity which also velocity which also depends on gradientdepends on gradient

River Sediment River Sediment TransportTransport

Sediment transported Sediment transported as:as: BedloadBedload

Saltation, traction, Saltation, traction, rolling of grains—e.g. rolling of grains—e.g. sand, pebbles, sand, pebbles, bouldersboulders

Most comes from Most comes from slopesslopes

Suspended loads such Suspended loads such as claysas clays

Most comes from soilsMost comes from soils Solution load from Solution load from

dissolved mineralsdissolved minerals

Deposition by Running WaterDeposition by Running Water

Braided StreamsBraided Streams network of network of

connecting dividing connecting dividing channels, separated channels, separated by sand and gravel by sand and gravel barsbars

develop when develop when sediment supply sediment supply exceeds transport exceeds transport capacity of running capacity of running waterwater

Deposition byDeposition byRunning WaterRunning Water

Meandering StreamsMeandering Streams defined by a single defined by a single

channel with broadly channel with broadly looping curveslooping curves

cutbanks are found on cutbanks are found on the outside of the outside of meanders, point bars meanders, point bars on the insideon the inside

unequal flow velocities unequal flow velocities in channels accounts in channels accounts for deposition and for deposition and erosion in predictable erosion in predictable patternspatterns

Incised Incised MeandersMeanders Develop where an Develop where an

older meandering older meandering pattern is cut into pattern is cut into underlying underlying bedrock as bedrock as tectonics uplift tectonics uplift the regionthe region

Channel Width and Channel Width and DepthDepth

Width mostly controlled by silt & Width mostly controlled by silt & clay in banksclay in banks More cl & slt = wider channelMore cl & slt = wider channel The wider the channel the shallower the The wider the channel the shallower the

depth.depth.

The Significance of Base LevelThe Significance of Base Level

Base level is the Base level is the lowest level to which lowest level to which any stream can erodeany stream can erode River cannot cut below River cannot cut below

its mouthits mouth Sea level is taken to be Sea level is taken to be

the ultimate base the ultimate base level, but the rising of level, but the rising of the sea or subsidence the sea or subsidence of land over geologic of land over geologic time make this time make this concept a relative oneconcept a relative one

Local base levels may Local base levels may control erosion and control erosion and depositiondeposition

Graded StreamsGraded Streams Graded streams develop Graded streams develop

over time as a balance over time as a balance between gradient, between gradient, discharge,discharge, flow velocity, channel flow velocity, channel

shape, and sediment shape, and sediment load is reachedload is reached

• • The concept is an The concept is an ideal, but gives us a ideal, but gives us a model to understand model to understand responses to changes in responses to changes in these parametersthese parameters

Think about dams on Think about dams on our LA, San Gabriel and our LA, San Gabriel and Santa Ana RiversSanta Ana Rivers

Predictions of Adjustment Predictions of Adjustment to Base Level Changesto Base Level Changes

Malibu, Bolsa Chica, BolinasMalibu, Bolsa Chica, Bolinas Describe how these creeks would change and the Describe how these creeks would change and the

impacts that these changes will have on the sediment impacts that these changes will have on the sediment supply to beaches and other regions of the coast if :supply to beaches and other regions of the coast if :

Sea Level Dropped due to global coolingSea Level Dropped due to global cooling Tectonic uplift of coastal areaTectonic uplift of coastal area Sea Level drops and tectonic uplift of coast occurred Sea Level drops and tectonic uplift of coast occurred

togethertogether Sea Level rises due to global warmingSea Level rises due to global warming Tectonic down dropping of coastTectonic down dropping of coast A dam is placed on the mid-point of the creeksA dam is placed on the mid-point of the creeks A resistant outcrop occurs in the mid-point of the creekA resistant outcrop occurs in the mid-point of the creek Excavation of the creek bottom in the mid-point of the Excavation of the creek bottom in the mid-point of the

creek occurs because of gold miningcreek occurs because of gold mining

DeltasDeltas Flow velocity Flow velocity

decreases as decreases as water flows into water flows into lakes or oceanslakes or oceans deposition occurs deposition occurs

and may lead to and may lead to the origin of a the origin of a delta, which can delta, which can prograde as prograde as sediment is sediment is continually continually supplied by the supplied by the streamstream

topset, foreset, andtopset, foreset, and

bottomset bedsbottomset beds

Sacramento River DeltaSacramento River Delta

NASA

Ganges RiverGanges River

Nile RiverNile River

Mississippi DeltaMississippi Delta

Santa Clara RiverSanta Clara River

Nasa

Malibu CreekMalibu Creek

www.santamonicabay.org/.../ tabid/77/Default.aspx

LA RiverLA River

scmi.us/.../ ci-core/la-river

San Gabriel RiverSan Gabriel River

Nasa

Meandering Meandering StreamsStreams Oxbow lakes form Oxbow lakes form

when meanders when meanders become so become so sinuous that the sinuous that the thin neck of land thin neck of land between them is between them is cutoff during cutoff during floodsfloods

How Do Valleys Form andHow Do Valleys Form andEvolve?Evolve?

Valleys usually Valleys usually have rivers have rivers running their running their length, with length, with tributaries tributaries draining draining highlands on highlands on either sideeither side downcutting downcutting

occurs when a occurs when a stream has excess stream has excess energy to deepen energy to deepen its courseits course

FloodingFlooding

Rating Rating Floodplain RiskFloodplain Risk

Streamflow Streamflow MeasurementMeasurement

Most common Most common practices are dams practices are dams and leveesand levees both require large both require large

capital investments capital investments and constant and constant maintenancemaintenance

they are constructed they are constructed to control finite to control finite amounts of water amounts of water and sediment; if that and sediment; if that is exceeded the water is exceeded the water will end up in the will end up in the floodplain anywayfloodplain anyway

Estuaries

Where the Rivers meet the Sea Semi- enclosed body of water where

there is a mix of river and seawater, and mix of fluvial and marine processes

Mouths of many rivers flooded at last sea level high (last interglacial)

Boundary between fluvial and marine processes Influenced by tides

Tectonic

San Francisco Bay

Fjord

Chesapeake Bay: Drowned Shoreline

ESTUARYThe Netherlands

Barrier Island

Wetlands – lands covered with water all or part of a year Wetlands purify water, act as flood control, & help

stabilize shoreline. Are biologically diverse

Wetland Conditions Hydric (saturated) soils – formed under conditions of

saturation, flooding, or ponding long enough during growing season to produce anaerobic conditions in upper

Hydrophytic plants – adapted to thrive in wetlands despite the stresses of an anaerobic and flooded environment

Hydrologic regime – dynamic or dominant presence of water

Wetland Classification Chart

Major Categories General Location Wetland types

Coastal Wetlands:

Marine (undiluted salt water)

Open coast Shrub wetland, salt marsh, mangrove swamp

Estuarine (salt/freshwater mix)

Estuaries (deltas, lagoons)

Brackish marsh, shrub wetland, salt marsh, mangrove swamp

Inland Wetlands:

Riverine (associated w/ rivers and streams)

River channels and floodplains

Bottomlands, freshwater marsh, delta marsh

Lacustrine (associated w/ lakes)

Lakes and deltas Freshwater marsh, shrub and forest wetlands

Palustrine (shallow ponds, misc. freshwater wetlands)

Ponds, peatlands, uplands, ground water seeps

Ephemeral ponds, tundra peatland, ground water spring oasis, bogs

Physical/Hydrological Functions of Wetlands

Flood Control Correlation between wetland loss and downstream

flooding can capture, store, and slowly release water over a

period of time Coastal Protection

Serve as storm buffers Ground Water Recharge

Water has more time to percolate through the soil Sediment Traps

Wetland plants help to remove sediment from flowing water

Atmospheric Equilibrium Can act as ‘sinks’ for excess carbon and sulfur Can return N back to the atmosphere (denitrification)

Chemical Functions of Wetlands

Pollution Interception Nutrient uptake by plants Settle in anaerobic soil and become

reduced Processed by bacterial action

Toxic Residue Processing Buried and neutralized in soils, taken up

by plants, reduced through ion exchange Large-scale / long-term additions can

exceed a wetland’s capacity Some chemicals can become more

dangerous in wetlands (Mercury)

Value of Estuaries

Greatly influenced by river discharge and tidal mixing. Environmental conditions fluctuate widely. Biomass is high because estuaries have high

nutrient levels. Species diversity is low because fewer species

can cope with the wide fluctuations in temperature, salinity etc.

“nursery grounds” young stages develop in the estuary

(abundant food; low predation may move offshore to adult habitats

Riparian SystemRiparian System What is a Riparian Area?What is a Riparian Area? Riparian zones or areas have been defined in several ways, Riparian zones or areas have been defined in several ways,

but they are essentially the narrow strips of land that but they are essentially the narrow strips of land that border creeks, rivers or other bodies of water. Because of border creeks, rivers or other bodies of water. Because of their proximity to water, plant species and topography of their proximity to water, plant species and topography of riparian zones differ considerably from those of adjacent riparian zones differ considerably from those of adjacent uplands. Although riparian areas may occupy only a small uplands. Although riparian areas may occupy only a small percentage of the area of a watershed, they represent an percentage of the area of a watershed, they represent an extremely important component of the overall landscape. extremely important component of the overall landscape. This is especially true for arid-land watersheds, such as This is especially true for arid-land watersheds, such as those in Eastern Oregon.those in Eastern Oregon.

Functions of a Healthy Riparian System:Functions of a Healthy Riparian System:1. Sediment Filtering1. Sediment Filtering2. Bank Stablilization2. Bank Stablilization3. Water Storage and Release3. Water Storage and Release4. Aquifer Recharge4. Aquifer Recharge5. Wildlife Habitat5. Wildlife Habitat

Riparian SystemRiparian System

A healthy system would A healthy system would have some or all these have some or all these characteristics:characteristics:1.) High water table & 1.) High water table &

increasedincreasedstorage capacity,storage capacity,2.) High forage production,2.) High forage production,3.) Good shade-Cool water,3.) Good shade-Cool water,4.) Good fish habitat-Good 4.) Good fish habitat-Good

waterwaterquality,quality,5.) High wildlife habitat 5.) High wildlife habitat

diversity,diversity,6.) Vegetation & roots present 6.) Vegetation & roots present

totoprotect & stabilize banks,protect & stabilize banks,7.) Higher late summer stream7.) Higher late summer streamflows. flows.

•Denton Creek