Let's say you are planning to canoe a river in northern Canada or Alaska. A trip guide, which you got off the Internet, says the rapids are "mostly canoeable". The question is, which ones are not?
A river profile will provide the answers. Here's how to make one:
Now, take a hard look at your numbers: Are you too ambitious? The rule on northern routes is 15 miles a day, plus one "down day" in five for bad weather and the unexpected. Now, into my seventies, I think 10 miles a day is a better plan.
Make a table like the one illustrated (above), and enter the data. Example: The 800 foot contour line crosses the river at mile 63. The next contour (700 feet) crosses at mile 69. It's 6 miles from mile 63 to 69. Thus, the river drops 100 feet (800’-700’=100’) in 6 miles. Divide 100’ by 6 and you get 17 ft. per mile of drop over this distance.
To continue: The 600 foot contour crosses at mile 83. From mile 69 (the 700' contour) to mile 83 (600' contour) = 14 miles. Divide the 100 foot drop by 14 miles and you get a drop of 7 feet per mile.
To the experienced paddler, drop figures conjure a vivid picture of a river's personality. Three to 5 feet per mile is lazy cruising; 10-15 feet per mile brings a smile; 20 means a probable portage, and 30 or more approaches the limit of an open canoe. Exceptions abound and largely depend upon "how the drops occur" (i.e. whether they are spread uniformly over a long distance, or come as a single falls or short rapid). Rivers that have uniform drops — even in excess of 30 feet per mile — are often pleasantly paddleable. Many Arctic rivers flow at this speed and are nicely canoeable. When I canoed the Kautikeino River in Finland, a three mile section of river dropped 62 feet per mile — and it was "courageously canoeable!" Bottom substrate (sand or rock) is a clue: Sandy bottom rivers tend to erode uniformly and produce canoeable rapids; rocky ones, like those on the Canadian shield, do not.
SOME MAP TIPS
My book, CANOEING WILD RIVERS, 5th Edition, contains more detailed information on this subject. www.cliffcanoe.com
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