Here you can download the hole lesson plan in English and in French. On the lesson plan you can find all the picture you need for this lesson.
Module 1 : Functioning and challenges of riparian and riverine areas
Objectives of the modules - This module aims at defining what are riparian areas and at precising the roles and challenges of these environments in order to be able to realise a state of the art intervention.
Riparian forest :
Ripa - Ripa in Latin means the 'river side', i.e. the adjacent area between the aquatic environment and the terrestrial environment. The river side extends beyond the bank. It is a flat interface space.
Sylva : means forest
A riparian forest is an old-growth forest ( or primary forest) bordering a watercourse or any wetland, whether it be a narrow or wide body of water.
Its floristic composition and morphology are linked to more or less frequent flooding and/or the presence of a shallow water table.
On the banks of the watercourse below, one can see 1) the alluvial forest or floodplain and 2) the riverbank afforestation, which is located near the bank channel. The riverbank afforestation need to be subjected to river maintenance operations.
Area of land flooded by the watercourse during the highest floods.
Bankfull channel :
It is located between the riversides and usually occupied by the watercourse.
Geographical area of a watercourse headwaters, within which rainwater flows to a single outlet (the river and its tributaries).
The lowest flow level reached by a river during the annual cycle.
Appearance of water at the surface after an entirely underground circulation. It is a reappearance in the open air, at the end of its underground journey, of a surface flow which had disappeared upstream.
Tree growing on the bank of a watercourse, whose roots have been exposed by erosion due to flooding. The water has dug under its roots, making an empty pocket with no solid base for the tree stump.
Mowing refers to the cutting and exporting of reeds and other grasses growing in the water of ditches, rivers, canals, watringues (or watergangs) and other ponds or areas still in water.
Scan the QR-code and make the exercise about the definitions of The riparian zone.
You can choose between this words: natural forest, wetland, river
You need to complete this sentence: A riparian forest is a …… , located next to a …… or more generally a ……… , represented by a narrow border or a very wide corridor.
Scan the QR-code and try to find the match.
2 – Composition of riparian areas
Riparian forests are composed of softwood species such as willows, poplars, alders, or hardwood species such as ash, Scots pine, maples and oaks, etc.
Herbaceous plants are not dealt with here because, firstly, it would be difficult to draw up an exhaustive list and, secondly, riverbank interventions concern trees and shrubs. It is therefore not essential to know about herbaceous and aquatic plants in order to carry out river works.
In the diagram below, please click on the buttons to discover some specific species of the riparian forest.
In alluvial forests, we can also find forest species that can withstand waterlogged environments, such as the pedunculate oak, the Scots pine, poplars.
The extract from the guide below presents the main species present in riparian areas, detailing their botanical recognition criteria, their ecological needs and their role in the environment.
Scan the QR-code and link each tree specy to its picture !
3 – Vegetation dynamics and distribution
Naturally, and in the absence of maintenance, a riparian forest is naturally repopulated with first herbaceous plants, then shrubs and then trees.
A succession of vegetation can be observed following a disturbance (clear-cutting, flooding, windthrow, etc.), starting with pioneers and ending with hardwoods.
A management too regular of the vegetation will prevent this natural evolution and allow pioneer herbaceous species (nettles, brambles, etc.) to consolidate their place in the environment.
A lack of management will lead to an increased risk of log jams due to dead wood and a decrease in biodiversity.
Wetland plants (irises, rushes, sedges, etc.), which are often found on the banks of watercourses, should be preserved as they play an important role in the retention and filtration of pollutants.
4 – The multiple functions of riparian forests
Riparian forests have multiple functions :
A mechanical function allowing the stability of the banks thanks to the root system of trees and shrubs;
An ecosystem function in its own right, situated between the aquatic environment and the surrounding terrestrial environment;
A plant filter function, reducing diffuse pollution (nitrates, phosphates and pesticides) and improving water quality;
A function for biodiversity with a diversity of habitats and watercourse flow facies;
A heritage and landscape function.
5 – Regulatory framework
The owners of watercourses are either the State in the case of state watercourses, or private individuals in the case of private watercourses.
Maintenance is the responsibility of the owner of the public river domain, i.e. the State. However, the latter is only obliged to carry out the maintenance work necessary to maintain the natural flow capacity of the watercourse. The protection of the banks(*) against erosion is the responsibility of the riparian owners and the state-owned nature does not exonerate the riparians owners from their obligations to maintain the banks.
Regulations allow the land parcel owners adjoining a watercourse to do maintenance work on the watercourse in regard with their parcels. This is regular maintenance in accordance with article L.215-14 of the French Environmental Code, i.e. maintenance that aims to maintain the watercourse in its equilibrium profile (*), to allow the natural flow of water and to contribute to its good ecological status [...].
Regular maintenance of watercourses by the riparian owners is not subject to prior procedure under the Water Act, but must always respect the functioning of the watercourse and the natural habitats. This maintenance can also be carried out by the agricultural operator or the river syndicate when it exists (or the community) which can intervene within the framework of a multiannuChal maintenance programme.
Read the following document and answer the questions :
[ Document in French about the maintenance of riverbanks – to find an equivalent in the desired language]