Ottawa blogger Mark Bourrie has two very sensible suggestions:
Effectively, 363 days of the year, it's a traffic island and a minor tourism draw. One other day, November 11, it's a place of great reverence. On Canada Day, it's in the middle of a big party that becomes rowdier (and drunker) as the night wears on.
(a) Put some damn public toilets in downtown Ottawa. The place is a huge tourist draw, but this isn't TV land. People do have to pee, and, in that place and time, with a dense crowd, no foliage, and no place to go, I can see how it happened. It was stupid, it was a violation of a sacred site, but I'm not surprised and;
(b) If it needs a guard on Canada Day because of the crowds, put a guard on it on Canada Day. Don't waste the old vets' tax money by having donut eaters standing around the War Memorial day and night, summer and winter.
Related: Ottawa Guide