Drought, Wind, Fire

Lush Knysna – before fires of June 7th

Knysna is a town of 73,000 situated on the southern tip of the African continent, 489 kilometres east of Cape Town. It is surrounded by hills overlooking the lagoon which opens to the Indian Ocean. Knysna is one of the most scenic places on earth, and where we devote much of each year. Approximately 21% of residents live in the town center, with the remaining 79% residing in suburbs established as Black townships and Coloured-areas during apartheid.

Destroyed township homes

On June 7th 2017, bush fires in the vicinity of Knysna exploded out of control. Fuelled by winds of 90-100 km per hour, with gusts to 110km, and following 12 months of drought, fires raged out of control for days. Ten thousand residents were evacuated, as was the public hospital.

Estimates vary, but reports suggest the loss of at least 458 formal homes, 30 guesthouses/ B & B’s, and 150 formal and informal dwellings in the townships. This does not include the hundreds of homes damaged, but not destroyed. Over 1,000 firefighters from across the country battled the flames and Knysna was declared a disaster area. At least 38% of destroyed and damaged homes/businesses were uninsured. Over 2,500 jobs were lost. Seven lives, including 2 firefighters, were lost.

Knysna – July 2017

Knysna Fires : Five factors that produced the Perfect Inferno
Mark Dixon – Garden Route Trail – June 23 2017

Referenced in literature and rarely seen, a thermal wave is a sine wave flow of super-heated air associated with a fire. 

Heat from the fire rises, while the wind blows it horizontally before it touches down and ignites a new fire and then again bounces off downwind. The wave length of this thermal wave can vary between 300m and 1000m allowing it to jump over valleys and rivers and resulting in the seemingly random effect of single houses exploding into flames while those around them are left unscathed.

The superheated air rises from the flames and moves laterally driven by the wind.  …the high temperature heats everything before it, be it trees or a structure, which then erupts into flame spontaneously before any flame reaches the area. When this wave descends on a structure…, it forces the roof down with immense pressure while the extreme heat melts glass and disintegrates bricks.

Eyewitness accounts of this leading edge of the thermal wave describe it as a rolling ‘tumbleweed’ flying through the air at between 100km/h and 110km/h. The area beneath the peak of the thermal wave has been described by Knysna Fire Chief Clinton Manual as … a smokeless zone of earie silence and no wind.

Knysna June 2017

The following video depicts the aftermath of the fires, interviews homeowners, and speaks to the rebuilding process which lies ahead.

Video: Ná die vlamme (Get The Flames):   Click Here to Watch

               

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