Geomorphology

Lake Formation• graben- downfaulted trough; e.g. Lake Tahoe

• caldera- subsidence of magma chamber; e.g. Crater Lake, OR

• Landslides

• glacial activity- e.g. scour, morain dams, & ice melt

• solution- CaCO3 (limestone)

• Oxbow

• wind- playa lakes

• humans & beaver

Oxbow Lake

Fluvial Morphology

determined by geology of the site:

dendritic- deposits of uniform resistance

rectangular- follow faults

trellis- flow between parallel ridges

Stream Ordering System

method of numbering streams as part of a drainage basin network; the smallest unbranched tributary is called 1st order, the stream receiving the tributary is 2nd order, and so on.

Stream Ordering

Stream Type

1. ephemeral- channels not well defined; flow during and shortly after precipitation events

2. intermittent- generally flow only during the wet season

3. perennial- year round

spatial scale in lotic ecosystems

World

Continent

Drainage

Watershed

Stream

Channel Patterns

• straight, meandering, & braided

• sinuosity- degree of curvature and meandering

• pool/riffle sequence; stream energy is lost at the head of the pool causing deposition

Braided Stream

Sedimentation & Channel Patterns

• erosion- chemical and mechanical processes by which stream channels are formed

• agrade- increase slope/gradient through deposition.

Deposition

process where particles that have been entrained and transported are deposited.

factors effecting deposition

1. stream gradient

2. flow volume

3. particle size

4. impoundments

results of deposition

• delta- results when flowing water meets standing water

• alluvial fan- sediments are deposited on land after eroding from higher elevation

• alluvial flood plain-

Delta

Alluvial Fan

Alluvial Floodplain

Flow Classification

Sediment

Particulate Inorganic Matter (PIM)

suspended sediments; primarily silt and clay

Dissolved Organic Matter (DOM)

decomposed particulate organics (particles < 0.45 um); carbohydrates, humic acids, tannins, proteins, & alcohols

Particulate Organic Matter (POM)

• larger sized particles; leaves, woody debris, and dead animals

• important habitat & nutrients

• Fine Particulate Organic Matter (FPOM)- < 1mm- >0.45um

• Coarse Particulate Organic Matter (CPOM)- > 1mm