[Tagging] waterway=wadi problem

[Lukas Sommer]

> No! Flood prone means that they are expected to be flooded from time to
> time. Nothing about the design.

So you would have to tag also each wadi, each river and each lake
because this area is covered with water? Maybe the terms “designed”
and “expected” are missleading. But the question is: How can we
distinguish between “normal water” and “flood water”.

I think rivers – also intermittent rivers – belong to the first
category. Also fords belong to the first category, because the
defination of the ford is that here you cross water (and the water can
be intermittent or not). This does no harm, thought it is quite
“normal”.

However, other objects like the house you are living in probably you
do not want to be filled with water. If it is filled with water, this
will not be a normal-life situation for you. If your house is for
example in the nice city of Cologne (Germany) near the river “Rhein”,
than perhaps at least a part of your house will be filled with water
one time each year. So your house can be filled with water in a very
regular way, nevertheless this is not nice for you. Your house belongs
to the second category.

I think the key flood_prone should be applied only for the second
category. The wiki page of the flood_prone key is not really clear.
But texts like

> Flooded roadways are often very dangerous to cross and many people die each year as a result.

on the wiki page suggest the same thing. It’s not about the normal
ford, where you know that there maybe you have to cross water and that
normally you can do so without a big danger. It’s about the not-normal
situations.

> as this may help routing software to avoid potentially hazardous crossings if there has been heavy rain.

This seems to be the original idea of the tag. And it’s useful. In
most western coutries, a heavy rain isn’t a big problem – there are
well-working sewerage systems. But I assure you that there are other
parts of the world where this is different. If you are living in
Abidjan (Ivory Coast) and you want to travel during the rainy season
during a rainfall than you know that there are many roads that are
impassable: Maybe 20% of the paved routes can’t be used because the
water reachs 1 or 2 meters. (But most roads are unpaved. And unpaved
roads are evern worser when it’s raining ;-)

> I'd hope that the flood_prone tag would be
> applied to an area

I think both tagging – on areas an on highways – can be useful. Both
tagging are also present in the database.

> and best if the frequency is noted e.g. once every 100
> years.

Agree. (Though – every 100 years is a very risky description. At
places where floods occure more often – for example once a year –
predictions tend to be more reliable.)

> Again no. A ford may be continuously under water. E.G. a road that goes
> through a river .. where the river normally flows across the top of the
> road.  Some fords may only have water in floods, others seasonally, and
> others continuously.

That is what I said ;-)