Indian Rock Dam only controls one third of the total drainage area. Since 1920, there have been six months where the rainfall was greater than 10"; two of these periods resulted in floods, and the third a near flood; if these were evenly distributed, which they are not, the interval would be 15 years. The flood frequency in the last 256 years is grouped in three intervals — seven at 11 to 17 years, three at 34 to 39 years, and four at 2 to 5 years. I believe we will have a flood before 2010. If the Indian Rock Dam gate closings are timed to perfection, and the rainfall on the branches is distributed just right, York may not flood. The area covered with roads and parking lots increases the potential every year.

Meckley's paper, “The Codorus," remains the most authoritative look at all three branches of the creek, the main body of water flowing through the City of York. He covers the creek's hydrology and the history of flooding along the waterway, among many other things.

A copy of the report is available at the York County Heritage Trust archives. www.yorkheritage.org