Don't just assume it needs regrading without checking what's actually blocking it first - pooling water usually means either debris is damming it up or the grade has settled, and those need different fixes. Walk the ditch after the water drains and look for leaves, sediment buildup, or fallen branches that are obvious culprits, then see if the water's actually flowing slower or just stopping dead in certain spots. If clearing out junk solves it, you're probably just looking at seasonal maintenance; but if water still pools in the same spots even when the channel's clear, that's when the grade has likely shifted and you'd need regrading. Since this is a shared ditch, have you talked to your neighbor about what they've noticed, and do you know if it pooled like this before or if this is genuinely new behavior?