How rivers and burns work

Most Scottish Rivers are dynamic, sometimes causing serious hazards. Yet this mobile nature is the way that rivers work, responding to local climate, weather events (like heavy rainfall), landscape and different types of land use.

A rivers "work" is to transport sediment and water. Moving water can only transport sediment when there is sufficient force to overcome the strength of the sediment. Smaller lighter grains of clay and silt can be carried in suspension by moderate flows of river. But in general bigger sizes of sediment require stronger river flows to move them, which means the river needs to be sufficiently deep and fast flowing, which may only occur a couple of times a year during a flood. The larger sediments (coarse sands, gravels, cobbles and boulders) are moved by the flowing flood waters by bouncing and rolling the stones along the river bed.

Different parts of the channel experience different levels of erosion (removal and transport of sediment), and deposition (dropping of transported sediment). Erosion is the dominant process in steep and deep parts of the river, such as the outside of river bends and in deep scoured pools. Sediment is deposited in swallowing water, and where a river channel widens. Depositional landforms include gravel and sand bars, and shallows that cross the channel diagonally between pools, called riffles. During floods rivers can drop fine sands, clays and silts across inundated floodplains.

This river work creates different types of river character.

Scottish river types