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Chapter 16
Landforms Made by Running Water
This chapter focuses on running water as a land-forming agent. It examines the processes
by which running water moves sediments and shapes landforms at the Earth’s surface.
Landforms produced by running water dominate most of the Earth’s terrestrial
environments.
 Water is one of the four active agents of denudation (the others being wind, waves,
and glacial ice) that erode, transport, and deposit sediments at the Earth’s surface to
produce erosional and depositional landforms.
 The term fluvial is applied to the processes and landforms associated with the action
of running water.
 Fluvial processes can erode and transport soil particles from slopes and uplands
causing soil erosion.
 Rates of soil erosion and soil formation are in equilibrium on the slopes of most
natural landscapes. This is known as the geologic norm. Disturbance of this
equilibrium by human activity or natural catastrophes can lead to accelerated erosion.
 Some eroded soil particles are deposited immediately at the base of slopes to form
colluvium, while others enter streams and are carried downstream before being
deposited as alluvium along valley floors.
 A stream can erode material from its bed and banks. Soft materials can be effectively
eroded by hydraulic action, while hard bedrock materials can only be eroded by
abrasion.
 The stream load or sediment carried by a stream is transported in three ways: as
dissolved load, suspended load, and bedload. Suspended load is usually the largest
of these components.
 Stream capacity to carry solid sediment is dependent on stream flow velocity, which,
in turn, is dependent on channel gradient.
 Streams tend to a graded condition over time such that the channel gradient and
stream capacity are adjusted to move the average amount of water and sediment
supplied by slopes.
 Indicators of a graded condition are the development of a floodplain and a smooth
stream profile.
 Grade is maintained as landscapes are eroded toward base level and, in tectonically
stable areas, erosion can eventually lead to the formation of a peneplain.
 Floodplain development involves lateral channel shifting by bank erosion on the
outside of channel bends and deposition of alluvium in point bars on the inside of
channel bends. It results in valley widening and the development of alluvial
meanders.
 Large rivers with low gradients and wide floodplains are called alluvial rivers.
Meandering or lateral shifting of alluvial rivers produces cutoff meanders, oxbow
lakes, and other distinctive landforms.
 Tectonic and environmental changes can cause aggradation and degradation in
alluvial rivers and lead to the formation of alluvial terraces and entrenched
meanders.
 Fluvial processes are very effective in shaping desert landforms because of the sparse
vegetation cover.
 Some of the more distinctive fluvial landforms of arid regions are alluvial fans,
pediments, and playas.