Guys,

I would be posting most of GIS links on my weblog regularly. Here are some tools that we will use for special course on GIS for Civil and Environmental Engineering (ECIV 490 and ECIV 790).
 
http://www.hec.usace.army.mil/software/hec-ras/

http://blogs.esri.com/esri/arcgis/2011/10/12/arc-hydro-tools-version-2-0-are-now-available/

http://www.hec.usace.army.mil/software/hec-geohms/

http://www.epa.gov/athens/wwqtsc/html/swmm.html