Watercourse | Glossaire eau, milieu marin et biodiversité

Bankfull discharge bed

Sens technique

Limit beyond which the water spills into the floodplain. It corresponds to the high-flow (or morphogenetic flow). Calculating the width of the bankfull discharge bed is a convenient measurement unit to describe the relationship between the size of the watercourse and its

Source

According to OFB

Low-flow channel

Sens technique

Part of the bed in which there is always water. It corresponds to the low-flow. Also referred to as "summer bed".

Source

According to OFB

Bed

Sens commun

Part generally located in the valley bottom in which a stream flows under the effect of gravity. Depending on the flow, we distinguish the low-water channel, the minor bed, the average water-level bed, the bankfull discharge bed and the floodplain.

Source

According to OFB

Invert

Sens commun

Part of a shallow stream with fast flow whose surface is heterogeneous and "broken" above gravel/pebbles or gravel substrates.

Source

According to OFB

Facies

Sens technique

Morphodynamic unit of a stream having longitudinal homogeneity in the slope of the water surface and in the distribution of water levels, in the velocities of the flow and in the particle size of the substrate. The length of a facies can vary from one to several times the width of the wet bed. For example, we can mention three major types of contrasted facies: wet (relatively low slope, high water levels, low velocities); fast (high slope, high flow velocities, substrate mainly composed of large blocks ); and flat (average slope, average and uniform velocities, water level rather low, symmetrical and regular cross profile, medium and homogeneous particle size).

Source

According to Cemagref

River mobility area

Sens technique

Area of the floodplain within which the riverbed can move in accordance with the decree of 24/01/2001 relating to the exploitation of quarries. The river is a dynamic system, moving in space and time: it constantly adjusts to fluctuations in the liquid flow. These adjustments result in lateral translations allowing the mobilization of sediments and the functioning of aquatic and terrestrial ecosystems. The mobility

Source

According to Cemagref

Progressive erosion

Sens commun

Mechanism of sinking the riverbed propagating itself downstream. The starting point of progressive erosion is an action, often human, causing a deficit of alluvial materials (construction of a dam or a sill, abstraction of

Source

According to Cemagref

Erosion of river banks

Sens commun

Natural phenomenon, usually caused by the current, involved in the transport of sediment load and sediment recharge of streams. The erosion of river banks is causing migration of meanders, and ensures the dynamic functioning of the

Source

According to OFB

Dike

Sens commun

Structure in concrete, earth or rock, or a mere (compacted or not) earthen dike or levee for: channelling a stream and possibly protect its surroundings (floodplain) against flooding, and/or protect a defined objective, more or less specific (urban, industrial, agricultural) and sometimes surround it, and/or serve as a barrier for a water abstraction in the stream.

Source

According to Marcel Roche (hydrologist)

Downstream migration

Sens commun

Action for migratory fish to go down a stream to return to their breeding or growing place.

Source

According to Rhone-Alps Regional Council