A friend of mine here who is also planning a trip to Hawaii asked me, "So what's a flash flood, really?" That got me thinking. I've always heard about them but don't really have a good idea as to what they really are. Can anyone provide a better description than the ones in the usual hiking books and guides? I know if you get caught in a steep canyon-type area and the water level rises fast, that's what it is and you're out of luck.
But how common are they actually? (numbers) How many hiking deaths in Hawaii are due to flash floods? What are some warning signs more specific than, say, "rain?" How much of a warning, timewise, might you have (rate of water rise)? Is there really nothing you can do to increase your chances of surviving one? (Avalanches seem pretty hopeless, too, and most are,but you can increase your chances of surviving one by taking some precautions, and trying to swim above the snow as it moves you out, etc...) Has anyone ever been in a position to videotape one in Hawaii? Where can I get actual figures on hiking deaths in Hawaii?
I appreciate the information anyone has on these flash flood specifics. My friend is trying to gauge the risk of doing certain trails as well. I told him, hey, I know just the people to ask....!
Good questions about flash floods, Collette.
Generally speaking, I avoid valley-type hikes when rainy weather is predicted. So far, that philosophy has worked well.
I don't have any hard figures, but people are killed by or need to be rescued from flash floods here on Oahu. Cases in point: about a year or two ago, a woman died while trying to ford a swollen Waiomao Stream (Kaau Crater Trail); there is a monument for a Boy Scout who died in a flash flood in Koloa Gulch on the windward side; folks have perished on the Sacred Falls trail; I talked to a guy who had to be rescued when a flash flood hit while he was hiking up the rope sections of Maakua Gulch; etc.
The best advice to heed if confronted with a swollen stream is to seek the highest ground available and wait until the water recedes. In my view, it is far better to be *temporarily* wet, cold, and hungry if cut off by a raging river than to chance crossing it and being swept away and *permanently* dead.
In 1987, HTMC went to Halawa Valley and encountered flash flood conditions. I did not go that day. One year later we went and it rained also, and the water was a foot higher than usual, but the other people said _that_ wasn't flash flood, a flash flood is more serious .....