Business Continuity Plan for web application and database
Business Continuity can be a complicated beast and you'll need to involve affected departments/users to make sure everyone knows the 'plan'.  The main two things you'll tend to see over and over are: RTO (Recovery Time Objective) and RPO (Recovery Point Objective)

RTO basically is the maximum time allowed to get things back to 'normal' or at least functioning.  You would need to take into consideration small problems (server went down) to big problems (the building just exploded).

RPO basically is, how much data could we 'possibly' lose should a bad problem happen?  5 minutes, 1 hour, 1 day, NONE?

There are lots of good stuff on the Internet about this topic - I think it would be time well spent doing some internet searches for IT Business Continuity Plan.

Here are a couple of good articles right off the bat:

http://www.cio.com/article/2381021/best-practices/how-to-create-an-effective-business-continuity-plan.html

https://www.brentozar.com/archive/2014/05/new-high-availability-planning-worksheet/

https://www.brentozar.com/archive/2011/12/letters-that-get-dbas-fired/

https://www.brentozar.com/archive/2015/09/why-rpo-and-rto-are-actually-performance-metrics-too/