not good, go to the city, developer, and builder and stick it to them until resolved, if indeed they did not develop the land properly for residential homes. Good Luck.

If there is a local storm water utility/department contact them. Questions you need to ask & things you need to do:

1) Is the property located within the 100 year floodplain?
2) Is the area behind your house designed to be a detention or retention basin? (A retention basin will always have water in it and a detention basin will only hold and slowly release all the water over a set amount of time. This would go towards explaining the location of the outlet pipe.)
3) Ask to see the grading and drainage plan that was submitted and approved. Have the engineer that approved it explain the design to you.
4) Request a meeting on site with developer, builder and local officials. If they don't respond you could have your attorney write them a letter requesting the meeting.
5) Take pictures over a period of time, not only when it is raining but also during dry periods.
6) Find out if the detention/retention area is a "blue line stream". If it is the Army Corp of Engineers has jurisdiction.

If the above items don't result in a resolution you may want to contact an independent engineer to review all the information. Of course as a last result you may need to obtain legal counsel and purse the matter through the courts. Good Luck.