How to re-surface a road through a ford

[jb70]

With all the recent weather there has been a lot of images of vehicles fording rivers on made roads and it got me wondering.

I apologise if this is a question with a stupidly obvious answer but....

How are roads re-surfaced through fords? Presumably some dry up up at some point but not all so, how's it done?

[jbi]

http://en.wikipedia.org/wiki/Cofferdam

[Vladimir]

I was picturing a REALLY modified re-surfacing car made by Ford!

[otherman]

A cofferdam would be somewhat overboard for a ford crossing.

Normally you'd just dam off upstream and pipe through to downstream while its done. Since the pipe needs to be buried to get a fall the one they used last time will probably still be there.