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View Full Version : Determining Catchment Areas for rainfall

Porklet
06-05-2011, 03:38 PM
EDIT: I wasn't sure where to begin this thread so I chose this forum. I hope I was right.

I am working on a world map. After reading several sources on the subject (including a thread started by Redrobes) I have decided to determine where the Catchment areas are located amongst the mountain chains on the map. I have never done this before. I worked on a few of the smaller chains, but I wanted to get some insight as to whether, or not, I am doing it correctly. I have included a WIP .jpg below:

The mountains themselves are merely representative at this scale, but I am using them as a guide for the water flow. Obviously, the catchment areas lie between any two pink lines on along the ridge line, or what have you.

Any feedback would be appreciated.

36317

waldronate
06-05-2011, 11:24 PM
A catchment is a function of a atream of river. I don't see either of those on the map. If your goal is to determine how rivers will flow based on your map, I recommend simply drawing them from the mountain range to the nearest ocean. Smallish enclosed areas are likely to have internal drainage. A scale would also be helpful in determining the potential quantity of flow.

I built a small height field and ran a river computation on the results. The white areas between the river systems would denote the boundaries of the major catchments. I had planned to attach the file, but the upload manager didn't seem to want to be cooperative (perhaps it was an IE9 problem). http://www.ridgenet.net/~jslayton/Abathas_Catchment1.jpg has the intended attachment.

However, it's often easier to do river routing by hand than it is to fake it like this.

Porklet
06-06-2011, 01:42 AM
A catchment is a function of a atream of river. I don't see either of those on the map. If your goal is to determine how rivers will flow based on your map, I recommend simply drawing them from the mountain range to the nearest ocean. Smallish enclosed areas are likely to have internal drainage. A scale would also be helpful in determining the potential quantity of flow.

I built a small height field and ran a river computation on the results. The white areas between the river systems would denote the boundaries of the major catchments. I had planned to attach the file, but the upload manager didn't seem to want to be cooperative (perhaps it was an IE9 problem). http://www.ridgenet.net/~jslayton/Abathas_Catchment1.jpg has the intended attachment.

However, it's often easier to do river routing by hand than it is to fake it like this.

That is a lot of rivers my friend. The scale I am working with now is 1 pixel = 1 mile. It's only representative, and it's my first map so it's also experimental. I am just trying to coordinate all of the things I have learned about creating a realistic map based on earth-like qualities. The rivers I will draw are only be major ones until I do the regional maps. Those will contain 90% of the detail.

One question: When you reference small enclosed areas are you referring to the ares where the mountains are close together?

waldronate
06-06-2011, 09:35 AM
Small enclosed areas would indeed be the areas between mountain chains as you have in the center-right area.

The image tweak that I did was generated in such as way that it cannot have enclosed basins, so it wouldn't show on that map. The nice thing about automatic generation of terrains is that you can generate arbitrary amounts of detail such as rivers.

Porklet
06-07-2011, 07:04 PM
Small enclosed areas would indeed be the areas between mountain chains as you have in the center-right area.

The image tweak that I did was generated in such as way that it cannot have enclosed basins, so it wouldn't show on that map. The nice thing about automatic generation of terrains is that you can generate arbitrary amounts of detail such as rivers.

What do you use to generate random terrain?

waldronate
06-07-2011, 08:30 PM
I tend to use Wilbur ( http://www.ridgenet.net/~jslayton/software.html ) as I'm more familiar with it than other packages.

Porklet
06-08-2011, 02:20 AM
I tend to use Wilbur ( http://www.ridgenet.net/~jslayton/software.html ) as I'm more familiar with it than other packages.

Interesting software, thanks again again.