Yes, employers can and often do put these sort of provisions into such an agreement. If you have concerns about the non-compete, then you would be best served to meet with a qualified employment attorney as to same.
I agree with the advice provided by my colleagues. Including a non-compete as part of a severance agreement is common--and as with any contract you can always negotiate the terms of the non-compete. Understanding the restraints on time, geographic location and industry to which the non-compete applies is extremely important to know whether the amount of severance compensation you are receiving justifies stopping or limiting your capability to work in a particular trade, at least for a period of time. Know, however, that courts hold non-compete agreements enforceable so it is VERY important to consider the non-compete carefully. I also recommend consulting with an attorney to review the terms of the severance/non-compete agreement to fully advise you of your rights and liabilities.
This answer is for general informational purposes only and does not establish an attorney-client relationship.