Seems you are new to undernet so i guess you ain`t that familiar to our official helping channels so let me present them to you a bit:
#report-abuse - deals drones, flood bots, hacked boxes, network threats, cases of a user intentionally spreading virus/trojan or harmful codes.
#UserNameS - deals exclusively with usernames issues / questions
#CService - deals exclusively with X and registered channels issues so when a user joins the channel and asks about something else ( in your case a flood with bots ) we redirect the user to the right place to report it if he/she wishes to do so.
#zt - #nastrand - #arlington - are dealing with unregistered channels issues as in chanfix for opless or stolen unregistered channels
#Help - #UserGuide - general irc / undernet help
This channels i presented above are the primary locations where you can get help so in this case if you join #UserNameS and you`re asking about a flood they will surely redirect you to #report-abuse or firstname.lastname@example.org
to report it using your logs and if you wish to do so of course.
The x don`t get the flood ? The #Cservice don`t deal with Registered Channels ? Then who do that ? If not Cservice ... Who gone help ?
X doesn`t get flooded but if a server goes into net.split X will go also of course but it is still on-line on the other remaining servers which you can find on http://www.undernet.org/servers.php
#CService as i said deals with registered channels but not in the concern you are refering to - there are channels modes that can protect the channel like +r ( this channel mode will allow only logged users to join the channel ) and also there is +m ( this channel mode will moderate the channel and will allow only opped and voiced users to type in the channel window )
So, now to answer to your question directly if you wish to report a flood with bots or some other abuse of our network feel free to join #report-abuse or e-mail email@example.com
and paste the logs in the content of the e-mail ( do not attach any files / logs ) and be sure it will be verified and if found true will be taken care of. Welcome to Undernet and enjoy your stay