Farms of ‘underwater windmills’
could affect how sand moves around our coastal seas, affecting beaches, sand
banks, and ultimately the risk of flooding, according to Bangor University
oceanographer Simon Neill.
Writing in Planet Earth, Neill explains how tidal energy farms are like
“When tidal currents are fast
enough, they pick up grains of sand from the seabed, which are then transported
with the flow. This is like cars picking up passengers en route to their
destination,” says Neill.
“Extracting energy from a tidal
system, for example by installing a farm of tidal stream turbines or ‘underwater windmills’, will reduce the strength of tidal flows. This is like
the impact of roadworks, leading to a reduced flow of traffic. A reduced flow
of traffic means fewer passengers can be transported. In the sea, tidal energy
farms will similarly reduce the volume of sand transported,” continues Neill.
This movement of sand feeds into
the natural systems which protect our coastlines from storm waves, such as
beaches and offshore sand banks. If a large tidal energy scheme were to disrupt
the natural flow of sand, this could make our coastline more vulnerable to
storm impacts, and could lead to increased flood risk.
However, apart from the obvious
benefits of low carbon electricity generation, artificial interventions by
tidal-energy farms could lead to positive effects. Strategic placement of
tidal-energy farms could even be used to create a natural form of coastal flood
protection by artificially manipulating offshore sand deposits. However, such
geoengineering would have to be based on a sound understanding of the
underlying oceanographic processes.