Stair stepping is occuring during floodplain mapping

If the floodplain mapping is jumping about and not providing
you with a good edge of water, then it is highly likely that
the step size defined in the Advanced Water Surface Options
dialog box has been set too high.

By reducing the step size in the Advanced Water Surface
Options dialog box, we can produce a more accurate
edge of water.

Advanced Water Surface Options dialog box is used to
adjust the step size

The Step Size data entry contained in the Advanced Water
Surface Options dialog box controls how far ahead the digital
terrain model will look for the next intersection with the
water surface and ground surface. A smaller value will
produce a more accurate floodplain map.