Tuesday, September 28, 2010

5149 Square Kilometres to Drain

Spoke to my buddy in Bella Coola today, 2 bridges completely gone that they know of and approaches to several highway bridges washed away, along with portions of the road. They don’t expect road access to Bella Coola for some time, this means they lose the last of the tourist season and most of hunting season, that is not covered by disaster funding.

The main road into town

From the Bella Coola Blog

5149 Square Kilometres to Drain
I was looking at a report tonight, the Bella Coola Watershed-based Fish Sustainability Plan Stage III Final Report and found a nice map on page 8 which shows the 20 + sub basins that make up the Bella Coola River Watershed. What you notice is that the watershed area of 514,962 hectares or 5149 sq kms, that make up the total area of the watershed, the Atnarko River drainage is the largest at 180,000 plus hectares. Normally during our 'flood' events, the Atnarko River drainage would see far less rainfall than the rest of the watershed, because most of the Atnarko River is in the lee or rain shadow area of the Coast Mountains. This time, it is apparent that virtually the entire basin of over 5000 km was likely saturated with the 200 mm + (8 inches) of rain all at the same time, including the large Atnarko River basin which goes well into the Chilcotin. It's rare that an area of road in the Chilcotin like the area of Highway 20 near McClinchy Creek would wash out based on rainfall of coastal monsoon levels.

If you think about the volume of water which 200 mm equals spread over 5000 sq km, the amount of water which has to drain out of the Bella Coola River is really quite large. It's going to take awhile, especially since more was added to it today. The three months of dry weather with soil that was bone dry and takes a long time to wet, didn't help our situation.

No comments:

Post a Comment