Unless you are making a complete raised floor on sleepers for the entire laundry room, I think you are merely making problems for yourself. It's already difficult enough for most people to bend down into the washer to remove items, and raising it up higher than the surrounding room will make it doubly difficult.

Are your concerns about general basement flooding or the washer itself flooding? Either of those two scenarios have other better solutions than building a platform for the washer.

The washer machine and dryer are near the water heaters and the possibility always exists that they could leak at sometime. I want to be prepared. Any additional thoughts?

Water heaters seldom have large leaks, the large leaks come from burst washer hoses.

The other bad water problems come from flooding.

My point? Putting a top loading washer on a pedestal to avoid those scenarios is basically useless. You would need to use concrete and make an area large enough to stand safely on. That means several yards of concrete, which could add enough weight to one area of the basement to possibly cause settling problems.

Building a wooden riser is less weight and cost, but will possibly cause more vibration noise.

If there is a drain in the basement, none of that should be necessary. No drain, the possibility of high water deep enough to rise above the platform due to burst hose of flood would only take a matter of hours. If you really have a fear of water damage, spend the money on a sump pit and pump system with a battery back up.

Just buy auto shut off supply hoses. They detect any water leak and automatically shut off. They're about $30. Then buy a water sensor alarm. They're about $20 and they will emit a high pitched shriek as a backup to the auto shut off hoses. Belt and suspenders. All for around $50. (Plus do what handymac suggests about a floor drain All basements should have a floor drain.)