Many worlds have an apocalyptic/cataclysmic event. If mine is a Great Flood, how long would it take for much of the world to be habitable land again? Keep in mind, by the events of the present, the surface of the planet should be ~65% water. The planet is, on average, colder than earth and circa the same size, and civilization doesn't need to recover, camps and villages will suffice. Also, how much would the geography change? And is there a chance of (RELATIVELY) intact artifacts and underwater ruins existing? The civilizations before the floods were quite advanced, so I don't think it's unlikely.
It can take however long you want, and the faster it goes down, the more destruction it causes.
Let's just assume that the planet was dry, and the water magically appeared. Maybe it fell from the sky (an inconceivable number of comets? Shell of ice around the earth?), but whatever happened, the entire planet is now covered with water.
Now we have to get rid of the water again. Barring un-physical things, we have to drain the water somewhere. Now, here is the fastest way of draining the planet that I can think of:
- Assume the planet had very few surface features - mountains are only hundreds of meters tall, valleys are only hundreds of meters deep. Maybe the whole world is only 3 kilometers in vertical distance from the tallest mountain to the deepest trench
- The entire world floods. You don't need as much water because the world is largely flat
- Wait 40 days and 40 nights....
- The sudden influx of water causes cools (or heats) the Earth's crust, and this causes massive changes in the tectonics
- The planets surface now has mountains 10's of kilometers high, and 10's of kilometers deep
- Water races into the trenches that formed, carving huge gullys and washing away everything.
How long it takes
According to the National Park Service, water takes three months to flow down the Mississippi river. I couldn't find stats for the Nile, Congo or Amazon, but at least we have one datapoint. In reality, you'd get dry land forming significantly before then, but you'd end up with lots of swamps that took even longer to dry.
This is only valid if you have a situation like the one presented above where all the water can go somewhere at the same time. The other option is a magic portal: https://what-if.xkcd.com/53/ This assumes a 10m portal draining the water, and it takes hundreds of thousands of years. Thankfully we are not required to use a 10m portal to drain the water from the great flood. So the time really takes however long you want.
The results of the draining
If you drain the water fast, nothing will survive. Water is hugely hugely destructive. Here are some videos for you:
- Tsunami: https://www.youtube.com/watch?v=oWzdgBNfhQU
- River in flood: https://youtu.be/tWGK4CiWxeM?t=4m30s
- Dam Burst: https://www.youtube.com/watch?v=xygVe0Vtv3w
We have a situation thousands of times worse. The ground will also change shape massively, forming new canyons. Big rivers can pulverise rock, so I think it's fair to assume nothing big of your civilisation is left. Maybe small chunks of ground up concrete and shards of metal, but likely nothing easily identifiable.