Quote:
Originally Posted by Riverman
I'm going to assume you were not there in 1997.
You can't use 2009 as any kind of a reference. It was a strange flood year that was caused more by ice than water. Localized ice jams caused strange level readings. Plus you have to remember that during high periods the surface of the river isn't "flat", i.e. it will back up and be higher behind restrictions like shallow areas and sharp turns.
Surveys are usually pretty close. If your dike was higher than needed it was probably because it was built with two feet of freeboard as they always are. Level predictions are just that - predictions. During the 1997 "Red Sea" event the engineers said one inch of rain in the flood area meant one foot of additional water in the city!
I can't remember what the slope of your yard looks like but when you say the water was 30 feet away, what was the vertical dimension? If the water goes up one foot it can eat up the yard quickly if it is a gentle slope.
Listen to the engineers and build the dike as they specify. Too high is better than too low!
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For sure, we would always build as per city engineers.
I was not here for 1997, but in 2009, we did indeed have two crests. The first was due to ice jams North of the city (which brought levels up to near 21 ft), then the 2nd crest was free of ice jams. This is when the water reading was 22.6ft @ James ave.
Our backyard is flat for the most part. When I say the water was 30 ft away, that is probably 2ft vertical.
However, it seems like the water at the Kildonan Bridge is consistently 2.5ft lower than James Ave during flood season, and approx 1ft lower than James the rest of the year. I've been documenting daily river levels in "April" since 2007. According the the city website, the water level at Kildonan Bridge is currently 1ft lower than James:
http://www.winnipeg.ca/publicworks/pwddata/riverlevels/
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Riverman, I have another question for you: Today, the city crew arrived to survey our property. Unfortunately, I was at work and unable to speak to them. The "numbers" they have written on the stakes seem to make no sense. For example, the stakes nearest our house has: 29.581
What does that number represent???
It can't be feet above datum or else I wouldn't seen sandbags. If it was feet above sea level, it would be 740 (or something). If it was metric, it would be 225 (or something).
Any ideas?