HEC 26 Spreadsheet
FHWA has developed a Microsoft Excel spreadsheet to facilitate the implementation of the HEC 26 AOP culvert design procedure. It follows the HEC 26 procedure step by step, performs the necessary iterative calculations, and acts as a bridge between the procedure and the hydraulic model that must be used to determine flow depths within the culvert (e.g. HY8 or HEC-RAS). The spreadsheet also contains sheets that plot given sediment gradations, perform a Wolman pebble count and plot, and identify the valid Manning's n-value functions that are available for a given application. Warning messages and notes are provided at appropriate steps in the procedure and general guidance on spreadsheet use is included at the end of the spreadsheet. The downloaded spreadsheet is preloaded with an example. Note the macros must be 'enabled' before use.