Breaching of the Bot River Estuary

As reported by Sue Matthews, Overstrand Estuaries Management Coordinator, with photographs by Meg Campbell
The Bot River Estuary was artificially breached overnight on Friday 17 August, following a
decision by a breaching subcommittee of the Bot River Estuary Forum (BREF) in consultation with estuarine specialists. The artificial breach was in accordance with a Mouth Management Plan approved by the Department of Environmental Affairs and Development Planning (DEADP).
The estuary last opened in July 2009, and the likelihood of it opening naturally was reduced by the opening of the Kleinmond mouth on Saturday 11 August, following heavy rainfall. Runoff entering the Bot River Estuary from the catchment had been exceeding the water lost through the Kleinmond mouth in the days prior to the artificial breach, with the result that the water level was at its highest in many years, at approximately 3m above mean sea level.
Environmental Management and Operational Services staff from the Overstrand Municipality met with a Cape Nature team at the sand berm opposite Meerensee on Friday evening to begin digging a trench with a municipal backactor. The breach was conducted under the supervision of a Cape Nature official who has overseen a number of breaching events at the estuary.
The final plug of sand was removed
shortly before 01h00, allowing the
first water to begin flowing through
the trench approximately 2½ hours
before high tide. This ensures that
the outflow strengthens with a
receding tide, reducing obstruction
by the sea. Peak outflow occurred
between 08h00 and 09h30 on Saturday morning, coinciding with low tide and thus maximising the scouring of sediments.
Timing the breach to ensure peak outflow during daylight hours is important in preventing birds such as red-knobbed coots from becoming disorientated in the dark and getting washed out to sea. No reports of dead birds were received. The breaching activities went according to plan and the operation is considered successful.

Preliminary test show that the Bot Estuary is looking healthy during the first round of monitoring of water physical-chemical parameters, with the salinity levels showing good mixing with sea water.