A reader, Jenny Patchett, recently wrote to Bolander (“River bank mess” , Bolander September 27,) about the work being done along the banks of the Lourens River in the vicinity of Somerset Oaks in Somerset West. Bolander submitted the letter to the City of Cape Town for comment, and received the following response from Brett Herron, Mayoral committee member for transport
and urban development:p>
The flood alleviation initiative in the Lourens River requires that we increase the capacity in the river channel in order to protect this neighbourhood and downstream areas in this part of the city from flooding.
These works are being undertaken to prevent widespread flooding that has been occurring in Somerset West and the Strand.
In terms of the record of decision or environmental authorisation that we received to undertake this work from the Department of Environmental Affairs and Development Planning (DEADP), this increase in river channel capacity allows us to widen, but not deepen, the river channel in order to allow for more flow space for floods.
Needless to say, in widening the river, the existing river banks need to be excavated to provide this increased flow capacity.
This widening causes a temporary loss.
What will follow from this is the inevitable loss of vegetation, trees and the like, albeit that this is effected with professional advice regarding what is to be removed or not.
The section of river that the reader is referring to pertains to the initial earthworks only, but does unfortunately not take into account or recognise the work that will follow in order to reinstate the newly formed river banks.
Depending on the steepness of the slopes after excavation, the newly shaped river bank and the “toe”, the meeting point of the sloped embankment and the river’s flow channel, will be vegetated with plants endemic to the river – in other words, those plants that occur naturally in the river and that are not invasive species.
This revegetation will be done in terms of an approved list of plants and with the guidance of a professional landscape architect that is a member of the team responsible for the flood alleviation initiative in the Lourens River.
The reinstatement of plants is accompanied by a two-year maintenance period to ensure that the reinstatement is successful.
Further measures that are used to also stabilise steeper slopes include gabion baskets and mattresses – wire baskets filled with river stone – and also “walls” formed by using interlocking concrete elements which are referred to as Löffelstein blocks and have been designed to function in water courses.
These blocks are also capable of receiving soil and plants to eventually form a reinstated river bank that, to a certain extent, resembles a natural vegetated river bank.
Even though I appreciate that in its uncompleted state the works may resemble a “dust bowl” as the reader suggests, residents may look to the opposite banks or other sections of the river where works are more advanced and the reinstated banks are being completed.
The project received approval from DEADP in 2001 after the necessary statutory processes, including public participation and landowner consent, were followed in coming to this decision. This includes public participation.
An environmental management committee is established at the outset of each phase, and anyone interested in the project is invited to become a member for the duration.
This invitation stands.
Email bolander@inl.co.za
