This document discusses fluvial landscapes and processes. It begins by defining base level as the lowest level a river can erode down to, which is ultimately sea level. It then describes how above base level, rivers engage in downcutting and have more energy for erosion. Closer to base level, rivers meander laterally and deposit material. Common landforms include meandering streams, floodplains, deltas, and entrenched meanders formed by tectonic uplift. The document also discusses drainage patterns, watersheds, stream flow, fluvial processes of erosion and deposition, and flooding events.

1. Fluvial Landscapes

2. Overview
Fluvial Processes
Basel Level
Down-cutting and meandering
Drainage
Watersheds
Drainage Patterns
Stream flow and fluvial processes
Meandering Streams
Floodplains
Flooding

3. Base Level and Fluvial Landscapes
A Profound Concept: Water flows downhill
Abrades and erodes the landscape as it happens
Abrasion = erosion process
Creates erosional landforms – drainage patterns, cut banks
Carries eroded material downstream as either dissolved,
suspended or bed load
Load = Transport
Load becomes deposited, creating depositional landforms
Depositional landforms: Deltas, point bars
Base Level: The lowest level that a river can erode
down to.
Gravity sets the water in motion
Ultimately, the water is trying to reach sea level
Local impediments to flow create local base levels

4. Higher above base level, water has more potential
energy, which gets converted to kinetic energy as
it flows downslope
Above base level, more energy directed downwards,
more able to erode bedrock - downcutting
Closer to base level, energy directed outward with
motion, erosion occurs more laterally - meandering

6. Landforms associated with rivers vary by how
high above base level the river is
Above base level
Steep V-shaped valley walls
Narrow stream channels
Distinct drainage patterns based on underlying
geography
Downcutting (erosion) and transportation are the main
geomorphological forces acting
Closer to base level
Wide stream channels (floodplains)
Valley walls characterized by terracing
Meandering river patterns, river deltas
lateral abrasion, transport and deposition
Tectonic forces can cause areas close to base level
to become uplifted
Meandering gives way to downcutting
Entrenched meanders, canyons

11. Drainage
When rain falls on a landscape, it drains
from higher to lower elevations
erodes surfaces as it happens
largely an erosional process
Occurs above base level - downcutting
over time, forms regions of consistent
drainage patterns that concentrate runoff
into specific streams and rivers
watersheds or drainage basins
drainage pattern

12. Watersheds
topography directs flow of surface water
into various downslope areas
at high points in the topography, surface
flow separates down different slopes, and
channels water into separate drainage
systems
these high points are called drainage divides or
interfluves
drainage divides form the boundaries between
watersheds

20. Drainage Patterns
Pattern relates to
underlying bedrock
Type of rock
Soft sedimentary layers tend to
produce dendritic patterns
Igneous or hard sedimentary
bedrock tends to produce
rectangular patterns
streamflow directed through
orthogonal rock fractures
Folding
produces trellis patterns

21. Dendritic
soft underlying
sedimentary rock
exerts no strong
directional influence
on the flow of water
most common
stream pattern
a radial pattern
occurs when soft
layers are uplifted
by an igneous
intrusion (dome) or
on mountain or
volcanic peaks

24. Trellis
Occurs where there is intense folding
antiforms and synforms
alternating layers of soft and resistant rock
Common in Appalachia

30. Rectangular
Occurs on areas with
resistant bedrock
Surface flow follows
rectilinear fracture
pattern of the rock
produces an annular
pattern when this
occurs on a dome

31. Parallel
Occur on steep
slopes
Deranged
Occur where
something has
disrupted normal
surface patterns and
processes, such as
glaciation

32. Stream Flow and Fluvial Processes
Streams run down
slopes
Potential energy is
changed to kinetic
energy
Discharge
Speed
Channel depth
Channel width
Fluvial Processes
Erosion: abrasion
Transport: load
Deposition

34. Load
Dissolved Load
Suspended Load
Greatest part
Bed Load
Traction
Saltation
General Principle: The greater the speed, the
more load a stream can carry
Slowing causes deposition
Largest and heaviest materials deposited first

35. Meandering Streams
Erosion and
Deposition
Undercut bank and
point bar

37. Floodplain
Formation
Widening of valley through meandering
process
Features
Floodplain
Natural levees
Oxbow lakes and swamps
Meander scars
Terraces

48. Entrenched Meanders
Landscape was once near base
level, and meanders formed.
Later, tectonic uplift caused the
river to be raised above base
level, recommencing down-
cutting, and carving these
canyons

53. Deltas
Deposition
River reaches sea level (base level)
Velocity decreases dramatically
Load is deposited
Distributaries

58. Flooding
Rating (10-year flood, 100-year flood, etc)
an expression of probability (10%, 1%, resp.)
Contributing factors
Rainfall, of course
Oscillations, hurricanes
Human activities that increase runoff and reduce
soil moisture storage capacity
urbanization (increasing paved surfaces)
agricultural practices
Midwest Flood of 1993, North Carolina flood
of 1999
1000 year flood events (0.1% probability of
occurring)
Contributed to formations of “Dead Zones”
Dead Zone (The Zone of Hypoxia in the Gulf of Mexico)
Pamlico Sound, NC