Recent work with full-scale experiments indicates that there are fundamental problems with standard curb inlet design equations when applied to depressed curb inlets of 10 ft (3 m) or longer. A full-scale laboratory experiment showed that the latter part of a long inlet does not have a simple linear water surface profile at 100% interception, which is assumed for the form of Izzard’s equation that is adopted for many common design approaches [including the Hydraulic Engineering Circular 22 (HEC-22) design equations recommended by FHWA]. For a long inlet, thin flow sheets were observed for a substantial portion of the inlet length, which is consistent with previous observations that have not been incorporated into standard design equations. Experimental results indicate that the HEC-22 design equations significantly overestimate the interception capacity of long, depressed curb inlets for an on-grade gutter. This issue has potential safety implications in that the gutter bypass and spread for a design storm will be larger than expected for such inlets. The present work is preliminary, so an L2 measure previously proposed by Izzard is recommended as a maximum inlet length pending the outcome of further studies.

Base Flow (1966-2009) and Streamflow Gain and Loss (2010) of the Brazos River from near Roby, Tex., downstream to near Noodle, Tex., and second from Hawley, Tex., downstream to Nugent, Tex. Most of the North Bosque River was characterized as gaining streamflow. Streamflow gains were identified in the main stem of the Brazos River from where the Brazos River main stem forms at the confluence of the Salt Fork Brazos River and Double Mountain Fork Brazos River near Knox City, Tex., downstream to near Seymour, Tex.

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