ASBOG Drainage Patterns/Stream Types 2

Question 1

What is a trellis drainage pattern, and what does it indicate about the underlying geology?

Accepted Answer

A drainage pattern with long parallel main streams joined at right angles by short tributaries, indicating alternating ridges and valleys of tilted, folded, or faulted rock

Answer

A drainage pattern with streams flowing radially outward from a central high point, indicating a dome or volcano

Answer

A drainage pattern with randomly branching streams, indicating a horizontal, homogeneous substrate

Answer

A drainage pattern with streams converging toward a central depression, indicating a basin or karst feature

Question 2

In the Strahler stream ordering system, how is the order of a stream reach determined?

Accepted Answer

All streams are assigned order 1 at the headwaters, and order increases by 1 each time two streams of equal order join; the junction of unequal orders retains the higher order

Answer

Stream order is assigned by the US Geological Survey based on total catchment area and length

Answer

Each tributary downstream junction increases stream order by 1 regardless of the tributary's order

Answer

Stream order is determined by the gradient — steeper streams have higher order numbers

Question 3

What is an antecedent stream, and how does its drainage pattern provide evidence for tectonic uplift history?

Accepted Answer

A stream that predates tectonic uplift and maintains its course by eroding downward as a barrier rises across its path, creating a water gap or gorge through an otherwise wind-gap ridge

Answer

A stream that follows a path predetermined by the regional slope of a newly emerged coastal plain; evidence of sea level fall

Answer

A stream that captures drainage from an adjacent basin by headward erosion; evidence of differential erosion rates

Answer

A stream flowing in the opposite direction from regional drainage due to thrust faulting; evidence of tectonic inversion

Question 4

What is the primary difference between a braided river and an anastomosing river system?

Accepted Answer

Braided rivers have multiple unstable, shifting channels separated by transient bars with high width-to-depth ratios; anastomosing rivers have multiple stable, vegetated channels with low width-to-depth ratios separated by floodplain islands

Answer

Braided rivers occur only in arid climates; anastomosing rivers only in humid climates

Answer

Braided rivers have higher sinuosity than anastomosing rivers; both transport bed load and suspended load

Answer

Braided rivers form only in mountain headwaters; anastomosing rivers only in coastal deltas

Question 5

What is the geomorphic significance of a 'yazoo stream' on a river floodplain?

Accepted Answer

A yazoo tributary runs parallel to the main river on the floodplain because natural levees block its direct entry into the main channel, forcing it to travel long distances to find a low point to join

Answer

A yazoo stream is a cutoff meander lake (oxbow lake) formed when the main channel cuts through a meander neck

Answer

A yazoo stream is a tributary that captures the main river by stream piracy during a flood event

Answer

A yazoo stream is the lowest-order headwater stream in a drainage basin, flowing from a spring

Question 6

What is the Hjulström-Sundborg diagram used for in fluvial geomorphology, and how does it relate to stream power?

Accepted Answer

It relates current velocity (or stream power) to grain size to predict erosion, transportation, and deposition thresholds for different sediment types, including the critical velocity for erosion of different grain sizes

Answer

It plots stream gradient against discharge to classify rivers into braided, meandering, and straight channel types

Answer

It shows the relationship between river sinuosity and valley gradient for different climate regimes

Answer

It predicts floodplain width as a function of drainage area and mean annual precipitation