Hydraulic Performance of Rectangular Deck Drains

The Texas Department of Transportation (TxDOT) Bridge Division has developed a new type of rectangular, scupper deck drain with two different sizes, 4" × 8" and 6" × 8". It allows runoff to drain via free fall without a pipe system. The new drain is designed to fit between the deck reinforcement and not interfere with the structural connection of the rail to the deck; therefore, it is less susceptible to clogging and requires less maintenance. However, no equation is available to accurately predict its hydraulic performance. Therefore, equations developed by Federal Highway Administration (FHWA) Hydraulic Engineering Circle 22 (HEC 22) for slotted drains were adapted to model its hydraulic performance.