Rhône Delta-Case Study

• Lies between the two major distributaries of the river Rhone; the Grande Rhone and the petit Rhone.
• The east branch, the Grande Rhone is the largest of the two branches and carries 85 per cent of the rivers water.
• The Rhone Delta has formed over the last 7000 years since the sea level rise at the end of the last ice age finished.
• The current shoreline began to take shape at the beginning of the eighteenth century when a flood moved the course of the Rhone to its present day position.
• This led to material at the mouth of the abandoned channel being moved to form the Beauduc spit.
• The total length of coastline is 90km and covers an area of 1740km.
• It is a lobated shaped delta that is dominated by waves meaning that waves re shape the delta by moving sediment at the edge of the delta by long shore currents.
• Waves come from two main directions. Most frequent wave direction is south west but these waves are of rather low energy, making this coast a low energy environment.
• Along the coast, areas of lagoons can be seen where longshore drift has moved sand to create lagoons trapped behind onshore bars and spits.
• The delta is very gently sloping. The coastal beaches are narrow with low dunes behind them.
• Climate change and the increase in temperatures are having an impact on the Mediterranean.
• A rise in sea level of 2mm a year since 1950 plus increased storm activity have affected the delta, leading to increased rates of erosion.
• The amount of material carried fell during the twentieth century as the Rhone river was managed to prevent flooding and for hydro-electricity production.
• The dominant wind direction typically has low wind speeds. As a result waves tend to be low in height and energy.
• Coastal landforms


  Interrelated and together make up characteristic landscapes
• Rhone Delta, France


  • Low-energy coastal environment
  • River Rhone flows into the Mediterranean Sea just to the west of Marseilles in southern France
  • Delta lies between the two major distributaries of the River Rhone; the Grande Rhone and the Petit Rhone
  • East branch, the Grand Rhone, is the largest of the two branches and carries 85 per cent of the river's water into the Mediterranean Sea
• How the delta formed

  1. Formed over the last 7000 years since the sea level rise at the end of the last ice age finished

  2. Current shoreline began to take shape at the beginning of the eighteenth century when a flood moved the course of one of the channels of the Rhone to its present-day position

  3. In the nineteenth century the mouth of the Grand Rhone changed position due to human management reducing it from three channels to one
• Rhone Delta


  • Lobate shaped delta that is dominated by waves (rather than the tide or river)
  • Deposits are typically sand and silt, with coastal beaches of fine sand
  • Enclosed shape of the Mediterranean Sea means fetch distances are relatively short in all directions
  • Dominant wind direction (NW) typically has low wind speeds
  • Waves tend to be low in height and energy
  • High levels of sediment accumulation from river deposition have created a gently sloping coastal landscape
  • Waves break early on the shore and their energy is dissipated by the beach and delta sediment
  • Deposition was estimated to be 17 million m³/year or 50 tonnes/min in 1900
  • River flow varies seasonally with a typical discharge of 1500 m³/sec, with up to 6000 m/sec in high flow conditions
  • Deposition varies seasonally
  • High deposition rate is due to the flocculation of clay particles
  • Small tidal range (0.3 m) also creates very few currents to carry material away
  • Amount of material carried fell during the twentieth century as the Rhone River was managed to prevent flooding and for hydro-electricity production
• Landforms of the Rhone Delta


  • Waves come from two main directions (SW and SSE/ESE)
  • SW waves are of rather low energy with heights of 0.5 to 1 m in 80 per cent of cases
  • SSE and ESE waves are higher energy waves, more than 2 m high in more than 40 per cent of cases
  • Sediment transport is split up into four cells
  • Cell 1 is dominated by SW-NE longshore drift which has formed the Gracieuse spit
  • Cell 3 has converging longshore drift currents, and this has resulted in the formation of onshore bars
  • Lagoons (known locally as étangs) can be seen where longshore drift has moved sand to create lagoons trapped behind the onshore bars and spits
  • Coastal beaches are narrow with low dunes behind them
  • Behind the dunes are the brackish ponds/lakes and lagoons
  • In the nearshore area there are longshore bars where backwash removes sand and deposits it, and between these there are longshore troughs
  • Dunes form when the winds blow from the sea, and dry sand is moved up the beach by saltation
  • Delta is covered by areas of brackish, saltwater marshes behind sand dunes and around the edges of the étangs
• Climate change and the increase in temperatures


  Affecting the Mediterranean, leading to increased rates of erosion of beaches and dunes
• Reduced sediment input from the rivers


  Led to a change in the relationship between sediment inputs and outputs in the system, resulting in rates of coastal retreat of between 2 and 8 m
• Authorities have spent €15 million on coastal protection, including groynes, rip rap and sea walls to try to restore the equilibrium in the system