What's on my mind.

23 March 2007

Anybody Seen Noah?

A comment on Whatever sent me to look at the flood map for where I live. As I'd already figured out, Noah will be floating by before my house floods. Well, maybe my house will flood but my parents live on top of the hill so the animals and I can just walk over there.

My house (and my parents for that matter) is in a X zone. On the map there are two X zones. Definition one is "areas of 500-year flood; areas of 100-year flood with average depths of less than 1 foot or with drainage areas less than 1 square mile; and areas protected by levees from 100-year floods." Definition two is "areas determined to be outside 500-year floodplain. I'm definitely not behind a levee; any of the others could apply but I don't think I live in a 100-year floodplain. What I found most interesting was the existence of two definitions for zone X.

The viewable map is a scan of a black and white map. Therefore, I choose to assume there is some stippling or light grey color, not picked up by the scanner, that would show which of the two zone Xs an area is, but why not pick another letter for one of them. As one who makes maps as part of my job, this is bad map making. I was taught to make labels, names, colors, etc. distinct. At least as much as possible, sometimes historical uses or names limit one. I was also taught to keep in mind reproducibility and the possibility that a color map may be printed B&W. It isn't possible to be perfect (too many dash patterns can make one go crazy!) and I don't know how old the actual map is (possibly before color printing or scanning was economic). Maybe the two zone Xs have always been used. If so shame on flood mappers of old (for starting this) and new (for continuing). Yes, in the long run the difference is very small between the designations. But it still an iffy choice.

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