Chapter 16- Fluvial Processes Flashcards
What’s the difference between streamflow and overland flow?
- runoff that flows down the land slopes in broadly distributed sheets is called overland flow. This is different from streamflow, in which the water runs along a narrow channel between banks.
What is a drainage basin or watershed?
- an area drained by a river system
How are stream orders classified within a drainage basin?
-stream order is a positive whole number used in geomorphology and hydrology to indicate the degree of branching in a river system
-first order stream: has one tributary
-second order stream: two tributaries
-so on and so on
-streams of higher order display channel complexity, with numerous islands and side channels that contribute to the overall network density
What are the types of fluvial erosion and fluvial deposition?
- fluvial erosion: A)vertical erosion B) lateral erosion
-canyons, gorges, river valleys waterfalls, river meanders, oxbow lakes
-fluvial deposition:
-natural levees, floodplains, channels, sandbars, deltas
Streams move solid material in one of several ways depending upon particle size
By solution (dissolved), suspension (stream flow), saltation (bouncing), and traction (pushing). - Alluvium: deposit of clay, silt, sand, and gravel sediments left by flowing water in a river valley or delta. - Stream competence – largest particle size carried / Stream capacity – maximum solid load transported.
What’s the difference between perennial and intermittent streams?
- perennial stream always flows in some parts all year round during years of normal rainfall
-intermittent streams normally stop flowing for weeks or months each year
How do we measure streamflow?
-the float method (or cross-sectional method) is used to measure flow rate.
-it is found by multiplying a cross sectional area of the stream by its velocity of water.
What is meant by a flood recurrence interval?
-return interval of a flood
-the likely interval of time predicted between floods based on evidence of old flood patterns
How are sediments carried in channel flow?
Structural relationships What are consequent and subsequent streams?
-consequent streams: streams whose course is a direct consequence of the original slope of the surface upon which it developed
-subsequent streams: streams whose course has been determined by selective headward erosion along weak strata. These streams have generally developed after the original stream
What are antecedent and superimposed streams?
-antecedent streams: stream that maintains the original course and pattern despite the changes in underlying rock topography
-superimposed streams: a stream that was established on a new surface and that maintained its course despite different lithologies encountered asit eroded downward into the underlying rocks.
-both are similarly not adjusted to regional geological structures and slope and thus are anti-consequent streams
Most common type of stream drainage patterns is dendritic.
How do floods deepen valleys
Why do streams meander (widen) and cause headward erosion(lengthen)?
-streams meander to maintain equilibrium.
-the formation of meanders in straight rivers and streams is largely dependent on disturbances. At the site of the disturbance, the path of the stream and the velocity of the current change, altering the behavior of the watercourse and resulting in the development of meanders
-headward erosion is a fluvial process of erosion that lengthens a stream/valley/gully at its head and also enlarges the drainage basin. The stream erodes away at the rock and soil at its headwaters in the opposite direction that it flows.
What is knickpoint migration (e.g., what’s happening at Niagara Falls?)
- a knickpoint is a part of a river or channel where there is a sharp change in channel slope, such as a waterfall or a lake
-knickpoints migrate upstream due to bedrock erosion leaving in their wake deep channels and abandon floodplains.
Floodplain landforms What are cutoff meanders (oxbows) and natural levees?
-an oxbow is a meander of a stream that has become separated from the flow of water
-a natural levee is a wall that blocks water from flowing, an elevated section of land that forms along a riverbank or coastline
