You might want to read the code in ifdown-route & ifup-route. Wouldn't it be a lot easier to shut down the interface (ifdown <interface>). That will flush the routes. Your problem may be due to shutting down the local host route.
From browsing the script, running "ifroute-up" sets an ACTION variable to "replace". This sounds like you can run ifroute-up to flush and replace the routes.
I'm using SuSE, but there may be a similar script in rhel. Try grepping files in /etc/ for the string "ip route" or better yet "static-routes". The script you find may do exactly what you want.
This webpage has examples of using "ip route flush".