I got reeeeal sick of having to Google© the console command every update, so I am making a guide that is just that command.
I made this entirely for the sake of my own laziness tbh fam.

SO

1. Open console with "~" key
   
2. copy and paste (without triangle brackets) <setbind LeftAlt "Duck | Jump" 1>
   
3. The crouch-jump is now bound to left alt key!

You can perform the long jump by tapping ALT or C just before hitting jump (on default controls) or whatever you have crouch mapped to, but I prefer having it mapped to a button. You can also obviously change the keybind to whatever you want (I'm a fan of setting both jumps to Mouse wheel up and down so i can do sick wall jumps Mirror's Edge speedrun style). If you haven't, you'll need to turn off toggle crouch to avoid jumping into a "sh1t my pants" walk.

Thanks to http://sp.zhabite.com/id/rechyysix for the link - all the keybinds can be found here [udn.epicgames.com] and you can't bind any button/key already in use in the control menu.

Enjoy your faster, longer (slightly shorter) jumps, and remember

DON'T SPAM KIRA'S ORBITAL!


On a side note: You can create an autoexec.cfg. It will automatically execute the command when you launch the game. So when the game updates, you will keep your long jump keybind.

• First go to your Dirty Bomb folder (YourDriveLetter:Steam\steamapps\common\Dirty Bomb). And go to the Binaries subfolder.
  
• Create a new text document and rename it "autoexec.cfg" (without the quotes and remove the .txt at the end)
  
• Now add your long jump keybind command in the autoexec file. Also you can add "Stat FPS" to display fps, it's a good way to make sure the autoexec works.
  
• Now to make Dirty Bomb run the autoexec when it launches.
  
• Go to your Steam Library and right-click on Dirty Bomb, Properties, and Set Launch Options.
  
• Add "-EXEC=autoexec.cfg" again without the quotes. Now your autoexec.cfg is ready. The command list is very limited in Dirty Bomb compared to CS GO's autoexec, it terms of what you can add in there.