Memorial for County visionary and Flood control engineer Jack Rafferty. 
Granite blocks and two plaques surround the large oak tree that was the location of the Willow Waterhole Project groundbreaking.  Rafferty is remembered for his contributions to flood control in Houston.

See Houston Chronicle article by ZEN T. C. ZHENG:

Marker to note county visionary / Flood control engineer Rafferty remembered in memorial at Willow project