I wouldn't give this model too much credit. It's only as good as its inputs, which are weather forecasts and probably antecedent soil mosture conditions. How many times has the weatherman been wrong about how much precipitation we're going to receive in a storm? Since you've posted this message, it's already changed considerably, forecasting a much lower flow for the time in question. I say go for it, and have a good time. If the river is high, it would probably only be really high for a day. I've heard the waves become Grand Canyon sized, so you should have a lot of fun.