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