In contrast to previous ecological theories which considered floods to be catastrophic events, the river flood pulse concept argues that the annual flood pulse is the most important aspect and the most biologically productive feature of a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

's ecosystem

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. It is a geomorphological concept that describes hydrological conditions in lotic systems. The flood pulse concept describes "the dynamic interaction between water and land" within the aquatic/terrestrial transition zone (ATTZ).

Background

River flood plain systems consist of an area surrounding a river that is periodically flooded by the overflow of the river as well as by precipitation, called the aquatic/terrestrial transition zone (ATTZ). The ATTZ is the area only covered by water during the flooding. This flooding in turn creates unique habitat that is essential to the survival of many different species. The flood pulse concept is unique because it incorporates the outlying rivers and streams which add a lateral aspect to previous concepts. From this lateral perspective, rivers can be seen as a collection of width-based water systems.

Flooding consists of multiple stages. First, at the start of the flooding, nutrients rush in from the area where the flood begins. During flood periods, the most important element is called the moving littoral

Littoral

The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...

. As flooding begins and water levels increase nutrients that have been mineralized in the dry phase are suspended with sediments in the flood waters and main river. The moving littoral consists of the water from the shoreline to a few meters deep in the river. This pulse of water is the primary driver of high productivity and decomposition rates as it moves nutrients in and out of the system and is good breeding ground for many species of estuarial organisms. At this point in time production rates exceed decomposition rates. As water levels stabilize, decomposition rates outpace production rates, frequently contributing to dissolved oxygen deficiency. When the water starts receding, the moving littoral reverses, concentrating nutrients and contributing to phytoplankton

Phytoplankton

Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

 growth.

Living communities and food types

The flood pulse helps maintain genetic and species diversity in the flood plain ecosystem, and it brings in oxygen to help fauna and decomposition. The flood pulse also increases yields by increasing the surface area of water and showers the land with river biota. Flood plain systems also serve as migration routes, hibernation

Hibernation

Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...

 spots, and spawning locations for many species. However, the flood pulse has the potential to overpower some species; when flood pulses occur at unusual times or last for too long, terrestrial vegetation can be overwhelmed. Furthermore, the receding of the flood at the end of the flood pulse can lead to oxygen deficiency.

Human impact

River flood plain systems can be both natural and man-made; the latter occur when dams

DAMS

Driot-Arnoux Motorsport is a racing team from France, involved in many areas of motorsports. DAMS was founded in 1988 by Jean-Paul Driot and former Formula One driver René Arnoux. It is headquartered near Le Mans, only 2 km from the Bugatti Circuit.- History :The year after its foundation,...

 and levees create a flood plain. Humans have had several effects on the flood pulse. Through ecosystem alterations such as dams, debris removal, channelization, levees, navigation, irrigation, contamination, logging, fire suppression, species introduction, and agricultural runoff, humans have contributed to the destruction of wetlands and the extinction of species. Biota relies on the flood plain for food supply, spawning and shelter, and flood pulses that are too quick or slow interrupt this. This can have devastating effects on riparian ecosystems.

Criticisms and alternative concepts

The flood pulse concept is one of three primary models describing large river ecosystems. The others include the river continuum concept

River continuum concept

The River Continuum Concept is a model for classifying and describing flowing water, in addition to the classification of individual sections of waters after the occurrence of indicator organisms...

 (RCC) and the serial discontinuity concept. Related theories include the nutrient spiraling concept. Many theorists have criticized the flood pulse concept and believe that other concepts could help explain the phenomena that occur in large rivers. Some say that the flood pulse concept is inadequate because it only applies to temperate and tropical

Tropical climate

A tropical climate is a climate of the tropics. In the Köppen climate classification it is a non-arid climate in which all twelve months have mean temperatures above...

 systems. The flood pulse concept involves many assumptions; many theorists object to the concept on the basis of these assumptions. The flood pulse concept assumes that all systems are either hierarchical or linear, that physical features control biological structures, and that there is dynamic equilibrium

Dynamic equilibrium

A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change. It is a particular example of a system in a steady state...

 between the biological and the physical rhythms. Because of their criticisms of the flood pulse concept, some theorists prefer the river continuum concept. However, Junk et al. argue that the river continuum concept is not sufficient because it is based on research done on small temperate streams and has mistakenly been applied to all water systems; furthermore, the river continuum concept does not explain habitats that fluctuate between lotic and lentic states, whereas the flood pulse concept adequately covers these systems.