You can run Walnut quite a bit above 2000 CFS, you must be aware that around this level, The Tubes (Marajuannica Falls) becomes extremely sketchy. Local paddl
You can add almost 8 miles of Class I and II by accessing the creek behind the Cinnamark Millcreek 6 movie theater. From there down to Millfair, rapids are spread out but some are pretty major Class II's. One worthy of mention is just upstream of a bridge no more than a couple of miles below the Mall. It is very narrow and has a huge hole. It may be caused by altering the streambed during the bridge construction. You won't need much more water to put in all the way up at the mall since Walnut gains no major tributaries during it's course from the the Mall to Millfair, but just make sure you catch it early enough after the rain as the level will drop earlier up by the Mall. Average gradient for this section is 20 ft / mile.
Playspot
I
Rapid
Playspot
II
Hazard
II
Playspot
I
Playspot
II
Playspot
II
Playspot
II
Hazard
II
Hazard
II+
Playspot
II
Playspot
II+