Lower Cowichan River – Elevated Flood Risk Hypothesis

Also available: sketch with hypothesized ‘Sequence of Events’ sketch series with a ‘Mitigation Design’ concept sketch

Outside the remit of 2017 contract work for waterbucket.ca, I developed the hypothesis that the 2009 Lower Cowichan River flood became unusually worse because of the volume of flooding coupled with the architecture of the estuary.

The hypothesis is that the architecture (the natural and built topography and the ocean bottom of the exit to the sea) in certain conditions unusually leads to the creation of what I’ve termed “Saltwedge Lakes” and “Saltwedge Dykes” (the coined term “Saltwedge” referring to the hypothesized shape of formation of “salinity differentials”; which is the salinity differences of freshwater and saltwater meeting in a confined space).

Click for larger picture

This can be imagined as something like a snowballing mini-tsunami of back-flooding that constantly rises as it ricochets. Private investigations led to the learning that the phenomenon is not well known and is hardly studied. If occurrence is validated here, it is fair to be concerned that it will replicate and be worse in this era of Atmospheric Rivers and Sea Level Rise. Also available, a nature-respecting flood defences’ concept; an idea to mitigate damage to the subject area.

Perhaps modeling will lead to placement of “Cowichan River Back-flooding Early Warning Altimeter Buoys” in Genoa Bay and Cowichan Bay? Here is the note sent to one of the local governments [link].

Note: Developed in parallel with the validated hypothesis that a dangerous buried river channel flows beneath Koksilah Industrial Park. Channel presence confirmed by City of Duncan civil engineers: See note here [link] and at “Research Director, Pringle Strategy Services”: https://www.linkedin.com/in/davehuer/