To relieve some of your boss's burden and prepare yourself and your direct reports for what's coming, study how your boss manages his workload. Make notes about his workload: Where is it coming from and when? Does it fluctuate wildly from light to heavy? It is a steady stream? Is it predictable or unpredictable? Develop methods to anticipate what future demands will be like so you're not continually taken by surprise.
Then help the Slave Driver put his workload and yours in perspective. Make it clear to your boss how the extra work ripples into your department or area and impairs your efficiency. Brainstorm ways that your boss can be better prepared for what's coming, not take on so much, or possibly fend some of it off.
Finally, write up a plan to deal with the work. Plan to finish the most important items first - don't waste time and energy giving equal time to everything. If somethings fall off the list so that your life can return to normal, make sure they're not important. Throughout, be positive and helpful. Support your boss and your staff.