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 Systemmethod 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 Type1. 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