Mt. Nusatsum

Mt. Nusatsum

Monday, September 27, 2010

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. Grizzly

4 comments:

  1. I am wondering what the maximum discharge measured on the Bella Coola river was during this flood?

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  2. just caught up on all the posts, this is terrible, my thoughts and prayers goes out to all who are struggling right now with this.
    you've put together very informative posts, thanks

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  3. That's a Lot of water, Grizzly. Too bad it all came at once. These devastating events are becoming more and more common everywhere.

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  4. Hello there Mr. Grizzly.

    Just a note to say thanks for having the Bella Coola blog available so folks outside the valley can get a sense of what's happening down there.

    I lived in the valley for a couple of years back in the early 90s and have friends there so this flood is of special concern to myself and my wife.

    Do hope for the best for you all.

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