Helene’s size shocked me but the storm surge for Katrina was unusually extreme. It was a well organized Category 5 and then weakened to a strong 3 right before landfall.
To compare with Helene, which was similar in terms of (east to west) diameter but covered much more area overall, with category 4 winds at landfall: the Weather Channel was making a big deal out of the 8ft storm surges. During Katrina, the Mississippi Gulf Coast had a 28 foot storm surge. (The Miss. Gulf Coast isn’t that geographically different from the Fla. big bend region but that plays a role too.)
Helene’s unusual movement speed kept it strong very far inland and caused massive issues in places that rarely see tropical weather. Harvey was the opposite: it stalled over Houston and dumped days of rain on a major metropolis.
I wish we could update the Saffir Simpson scale to something that takes into account more variables. There are other measurements but no storm is identical in terms of damage potential. A category 5 can not even make landfall whereas something like Hurricane Sandy was a category 1 (or equivalent since it wasn’t technically still a hurricane) when it hit NYC and caused massive damage and flooded subway systems. Sometimes, a storm hitting a place that isn’t used to them can knock over all the trees or flood rivers while a similar storm would be nothing to Miami or New Orleans.

I always want to reply with that chart on every post about some magical new climate technology. Nothing really matters until we stop pulling carbon-based fuels out of the ground and lighting them on fire. That’s it. That’s the only thing that matters. Wind and solar are great but we’re still approving gas/coal/oil projects, at least globally.
It’s like with the water crisis in the American West. They guilt trip individuals into feeling bad about taking showers but it’s like 80% agriculture. And the majority of that is for animal feed. (I’m not saying everyone go vegan. That’s about as unrealistic as asking everyone to stop fucking to keep the population from growing. I’m saying don’t grow alfalfa in the fucking desert and then blame people who bathe.)