Whenever I come to the Forum now, I have a Crappie time.
Doug, I have a couple of thoughts and some recommended reading.
1) ML is a major proponent here of natural spillways, which can work well for ponds in many situations. In addition to the precaution he mentions of wanting the overflows to stay away from the dam, you want to have the area that does receive to flow to be impervious to erosion. Some suitable surface materials for these areas, in increasing order of cost (and probably erosion resistance) are A) really good sod, B) heavy rocks, and C) concrete. See
spillway disappearing for one man's problems with a spillway that did NOT avoid going over the dam.
2) This really is currently the Crappiest Time in PB history. I have never seen so many discussions on Crappie that did not simply end with "Get rid of them." I believe Crappie may be the next fish that some folks seriously experiment with and figure out what precautions and management measures are needed to allow small pond owners to utilize Crappie to good advantage. ML, for all of his standard (dare I use the term "Tried and True"?) advice above, is probably going to be one of our Crappie experimenters (who knows, 'Lark could end up bestowed with the title "The Homer Swingle of Crappie"). So don't despair Doug, we're gonna figure out how to handle Crappie, and you can be part of the effort.
Here are some of the recent Crappie threads for your perusal:
crappie info for ponds HSB and Crappie