Since no one else has offered any suggestions yet I’ll try to give some ideas. Avoid island maps and lowland maps because the hydraulics aren’t interesting: you just end up pumping storm water into the ocean. Very large rivers are also not very interesting because it takes a lot of rainwater to notice any change in the river. The best maps have multiple drainage areas that flow into creeks that drain to river(s) that may or may not end in a large lake or ocean. You can use move it! And prop anarchy to place a bunch of Natural Drainage assets all over the hills. Run a storm and see where all the storm water naturally goes. The annoying part is fixing rail and roads so that they can handle the rain water. If you don’t like having NDAs everywhere you can just plop a flood spawner upstream of where you’re building. If I haven’t mentioned it yet the cross the line mod is helpful if you aren’t unlocking tiles early. Hope that helps!!!

@[SSU]yenyang, thanks for the tips! These are very helpful.

Also, I should mention that I found, through searches, a map that was specifically designed with Rainfall mod in mod. You can see it here at https://steamcommunity.com/sharedfiles/filedetails/?id=816767347

It's pretty old, though, having been posted back in 2016, after which values may have been adjusted in Rainfall mod. Haven't tried it yet but from the looks of it and based on your tips, it doesn't appear to be suitable if you want to deal with flood management challenges. Like you said, oceans and wide waterways don't lend itself well to flooding challenges. However, the description did not explicitly mention flooding so it is unclear whether it does or did indeed flooded or not during gameplay on this map.

Here’s a good one. I haven’t played it myself but it matched my recommendation.

https://steamcommunity.com/sharedfiles/filedetails/?id=2178197984&searchtext=

You might want to customize it by removing some of the smaller water sources and either replacing them with Natural Drainage assets over the area or a flood spawner.

Originally posted by SSUyenyang:

Here’s a good one. I haven’t played it myself but it matched my recommendation.

https://steamcommunity.com/sharedfiles/filedetails/?id=2178197984&searchtext=

You might want to customize it by removing some of the smaller water sources and either replacing them with Natural Drainage assets over the area or a flood spawner.

Great looking map! Which city setting would you recommend for rainfall there, to potentially make rivers flood during the rains? Houston probably most likely could do that but that might be the most extreme. xD :P

Are the cities listed within the setting in the order (e.g. lowest to highest average amount of rainfall or something like that)? Mind you, I just started playing Cities Skylines again after a long time without playing it so I am a bit rusty here and there.

Houston is really crazy. I recommend the Seattle setting. I think it has the best game play.
Limit the max intensity if it becomes too much.

I am in the process of designing a map with 'Rainfall' in mind. I am curious if there are any plans to extend the runoff effects to outside of the 25 tile, or if you know of a mod that will allow for the extended runoff. Thanks for a great mod btw.

#Kailizzrham It used to work beyond 25 tiles if you had 81 tiles mod and the setting for 81 tiles of runoff. I haven't tested it with the new version of 81 tiles for this version of the game.