Use the gravity gun to pull an exploding barrel near you. Wait for a bunch of them to gather below you. They shouldn't be able to jump up to you. Then blow up the barrel. Repeat until you've killed enough to make it across without getting raped.
This is a really great game, props to valve. I'm having some graphic/audio stuttering (which valve said they'd be fixing in an upcoming update), but the game still runs very well.