Hydromorphology

The word “hydromorphology” comes from “hydro”, meaning water, and “morphology”, meaning the physical features of the environment that is holding the water in place. These environments include rivers, lakes and transitional waters, such as estuaries, lagoons and tidal sections of rivers.

The aim of the Hydromorphology team at Inland Fisheries Ireland is to raise awareness of this important concept and to look for ways to improve issues within our environment that are related to changes in the natural hydromorphology of rivers. 

Interacting forces

Using the example of rivers, hydromorphology refers to:

• The amount of water flowing in a river, its speed and how it rises and falls during floods and droughts.
• The physical habitat of a river, including the type of channel bed materials, the variation in channel width depth, the type of river banks and the vegetation that grows along the slopes and tops of river banks.

Both components interact together. As water flows in a river, it travels against its bed and the banks, depositing (releasing sediment) and eroding (taking sediment). Flood waters transport different sediments, and the bigger and faster the flood, the larger the size of material the river can carry. Very big rivers, or very steep rivers coming down off mountains, can carry large rocks and boulders. As a flood eases and the energy of the river weakens, sediment drops down onto the river bed and changes the way a river looks, perhaps even changing its course.

The EU Water Framework Directive has put a spotlight on hydromorphology and is challenging us to understand how fundamental hydromorphology is in rivers, lakes and estuaries and in its influence on an ecosystem—the stage on which plants and animals function. 

There is no ecology without hydromorphology!

The Water Framework Directive helps to highlight the condition or status of waterbodies and if they are they in good condition or less than good condition. Good hydromorphological conditions in rivers, lakes and estuaries can facilitate good conditions for plants and animals. 

The human factor

Human activities have had a dramatic effect on hydromorphology. Building large dams and reservoirs has benefited humans by providing for hydroelectric power and drinking water supplies. Reclaiming land in estuaries and constructing large ports allow ships to transport goods all around the globe. Large drainage projects in rivers have helped to improve farmland and increase yields. Drainage, however, has changed the shape of rivers and the amount of water they can carry. Drained rivers have less physical variety, connectivity to the surrounding land and do not flood out as often. Their hydromorphology has changed! 

In the days before electricity, man-made barriers of all sizes in rivers were important for using the river’s energy to turn mill wheels and power all sorts of machinery, such as the millstones for grinding wheat to make flour for bread, or saws to cut large trees into planks for building. Hundreds of these barriers are still present in Ireland’s rivers, and most now serve no purpose. Many of them prevent our migratory fish species like salmon, eel, lamprey and shads from making their journeys between the sea and freshwater.

The hydromorphology team in Inland Fisheries Ireland also collaborates with the Environmental Protection Agency and the Office of Public Works.  We contribute to ECOSTAT, an EU working group on hydromorphology, as well as to the development of CEN standards for methods and to river restoration projects. We are a member of the Environmental Protection Agency’s Hydromorphology working group.