Depending on the type of DDoS, that may not do a single thing. There are plenty of ways to flood a connection without actually going up to the application running on the web server, or even the application layer of the OSI network stack.
At least in the past, I recall most of the attacks were either SYN floods, or just lots of requests against the webserver for a static file. Even a high enough rate of HEAD requests against, say, /community/Themes/smsite2/images/site/smsite_logo.jpg could cause the web server to have issues.