The Whelm spells are enchantments, which imposes certain limitations, but so do illusions. Looks to me like the designers put a premium on nonlethal damage by spell, which makes sense IMHO. Briefly:
Whelm: 1st level sor/wiz and beguiler; close range, one target; 1d6 + 1d6/2 levels above 1st nonlethal damage (max 5d6). Will negates, SR yes.
Whelming Blast: 2nd level; 30' cone; 1d6 + 1d6/2 levels above 1st nonlethal damage (max 5d6). Will negates, SR yes.
Mass Whelm: 4th level; close; 1 target/level; 1d6 nonlethal/level (max 10d6). Will negates, SR yes.
Overwhelm: 6th level; touch; one target; Will negates, SR applies; deal nonlethal damage equal to the target's current hps.