River and stream morphology
River and stream morphology, also known as fluvial geomorphology, is the scientific study of the shape, movement, and behavior of rivers and streams as they traverse their channels. This discipline examines how topographic features and environmental factors influence water bodies, which is vital for understanding watershed health and predicting reactions to weather conditions like storms and floods. Rivers and streams have historically been crucial to human society, providing transport, freshwater, and irrigation for agriculture. However, they also pose risks, such as flooding, which can lead to significant damage.
The study of river and stream morphology encompasses a range of elements, including water composition, sediment dynamics, and the impact of both natural environments and human activities. For example, human interventions like pollution and dam construction can dramatically alter these waterways, affecting biodiversity and ecosystem health. This field of study also plays a key role in river restoration efforts, as understanding a river's characteristics can help return it to a more natural state. By examining variables such as discharge, water velocity, and channel features, scientists can gain insights into the complexities of river and stream dynamics, which are essential for informing infrastructure development and conservation strategies.
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Subject Terms
River and stream morphology
In environmental studies, morphology describes the study of how topographic features like mountains, forests, and bodies of water interact with and are shaped by their environment. River morphology and stream morphology, therefore, are terms used to describe the study of the shape and movement of various bodies of water as they travel through channels. It may also be called fluvial geomorphology. Understanding river and stream morphology is important to the study of the health of watersheds and predicting how they will react to various weather conditions such as storms, droughts, and floods. Environmental engineers, environmental geographers, ecologists, and biologists all use river and stream morphology in their studies.
Background
Rivers and streams have played a key role in the development of human society. For the earliest humans, they offered a source of transport and food. Many of the first settlements were built on the shores of rivers to benefit from the many advantages they offered—particularly as a source of freshwater. The Romans built aqueducts that relied on rivers and rains to water crops and supply water to communities. Farmers quickly learned to build irrigation channels using streams to water their crops. Beyond their beauty and life giving nature, rivers and streams are unpredictable and potentially dangerous, occasionally causing deadly and damaging floods. At their most volatile moments, rivers have been able to carry huge boulders downstream during flash floods. Learning the habits of streams, a key component of river and stream morphology, has enabled scientists to better predict dangerous events and potentially prevent them from occurring. By the same token, watermills and dams have allowed humankind to harness the kinetic power of streams to create energy.
Rivers and streams are constantly in a state of change, a condition driven by the unpredictable nature of water itself. Over time, waterways change direction, speed, and depth as they are affected by external factors. These may include shifts in sediment, changes to the health of their water source, and impediments from events like rock falls or factors such as dams. The natural environment is capable of affecting river and stream morphology. For instance, the growth of aquatic plants may serve to anchor sediment, while beaver dams have been shown to change water temperatures, raise water levels, and alter the speed at which water flows. However, human interference has been shown to have the most dramatic impact on streams. Pollution, dams, and the use of water runoff to fuel irrigation have all been shown to have major impacts on river and stream morphology. In part due to the outsized effect of human influence on the health of water systems, river and stream morphology has become a key tool in river restoration. Understanding all of a river’s cumulative traits can be used to return it to a more natural state.
River and stream morphology has a number of other important applications as well. For instance, salmon life cycles are dependent upon the natural processes of streams and rivers. Species of fish such as the salmon require river beds that naturally allow exchanges between surface and groundwater. Any changes in how a river operates can have a disastrous effect on fish populations.
Both the construction and decommissioning of dams are dependent on accurate studies of river and stream morphology. When waterway conditions were not considered in the past when building dams on rivers, the health of these channels often badly deteriorated over time. As a result, species diversity among both plants and animals was greatly reduced. In some cases, dams altered the flow of rivers to cause flooding episodes that badly affected upstream communities. Similarly, it is vital to understand fluvial dynamics when constructing roadways and bridges, as underestimating the size of floodplains during major rain events can lead to washouts of important infrastructure.
Overview
Streams and rivers are composed of a variety of elements that work together to shape their health and course. Even the water itself may be broken down into several components that merit individual study, including reviews of biological composition, temperature, and the effects of pollution.
As a field of science, river and stream morphology considers a number of interrelated factors that must take into account the entirety of a river’s course. If it is part of a larger network of rivers, the science must consider the full watershed. For instance, the Mississippi, the longest river in North America and fifteenth longest in the world, includes dozens of feeder streams as well as both freshwater and saltwater content. It discharges 593,003 cubic feet (16,792 cubic meters) of water per second into the Gulf of Mexico. Its health is of vital importance to the economic strength of the United States. Changes to the Mississippi’s flow and direction have impacted both the flora and fauna that rely upon it for survival and the communities that risk spring flooding on an annual basis.
In considering river and stream morphology, scientists rely upon the use of both observational and technical data. In creating a broader understanding of a stream, they examine the composition of the sediment in the channel as well as the materials along its banks, a region called the riparian zone. In addition, they measure such variables as stream or river discharge, water velocity, length and width of the channel, floodplains, wetted perimeter, bankfull elevation, water levels at flood stage, and the effects of such features as riffles, runs, pools, cascades, rapids, falls, chutes, and glides. Discharge is a measurement of the amount of water that moves past a single point over a standardized unit of time lasting twenty-four hours, one hour, and one second. Velocity is defined as the speed at which water moves. Bankfull elevation measures the height of water in a stream or river before it overflows from its banks and moves onto the surrounding floodplains. The wetted perimeter is the area of a water channel that is consistently wet.
Riffles, runs, pools, cascades, rapids, falls, chutes, and glides are terms used to describe specific zones of depth and speed that naturally occur along the length of a stream. For instance, a riffle is a very shallow area over which water still consistently flows, while a run is an area with a swift and uniform flow. Most streams and rivers are alluvial, meaning that they create their own channel shape by moving sediment from one area to another.
Bibliography
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