HydroToolBox is an Excel add-in that provides specialized functions for data and analyses commonly used in hydrology. These functions allow you to easily determine:
• Channel area and wetted perimeter from topographic cross sections and water stage
• Recurrence intervals from annual peak flow data
HydroToolBox is free and available for both Windows and Mac OS, including both Mac Excel 2004 and Mac Excel 2011.
Note: Because Microsoft no longer provides the same level of support for add-ins in Mac Excel that it does for Excel for Windows, the add-in for Mac Excel is slower due to a less direct interaction between the add-in and Excel (specifically, there is no SDK for Mac Excel). In this sense, the Mac Excel 2011 is still somewhat experimental -- please let me know of any problems you have using this version.