Out of these majors, what do you think would be the most beneficial?

New graduates of all four of these Majors have a high unemployment rate in this economy.

Civil Engineering and Architecture MAY improve in four years' time. but its a roll of the dice. Many economists are predicting two lost decades.

The most valuable in this job market of what you named is civil engineering BY FAR.

Urban planning is useless, there are hardly any positions for urban planners and most of those positions are going to go to architects and civil engineers anyways.

A degree in environmental architecture also gets you nowhere unless its an accredited B.arch program.

A b.arch from a NCARB accredited program is an ok career choice, but there is just way less demand for architects than engineers in this down economy. My girlfriend is a recent graduate from an accredited b.arch program and almost half of her graduating class aren't even pursuing architecture after putting in the tough 5 years to graduate. Some of her classmates are getting paid very well, almost on par with the civil engineering graduates, but most are making far less. And as I said there is far less demand for architects than engineers right now.

If you are concerned about money and the job market you should look into this website: payscale.com

Look at it this way:

The size of impact. Do you want to help Countries, States, Cities, Communities.

You have a better chance of making more of an impact doing Environmental Architecture because of it's global benefits.

Good luck!