* Measured in the thalweg during low water level conditions to provide a
conservative value for fish habitat suitability.
Another easily identifiable rock weir dimension related to fish passage
is the ratio of rock weir size to channel width. The width of a channel,
and subsequently the width of a constructed rock weir, influences the
number and size of keystones used. For example, a larger cross-section
requires more keystones, footer stones, and river stones to construct
the rock weir between channel banks. Fish passability under different
water level conditions was examined as a function of rock weir width to
determine if this design consideration can inform fish passage
effectiveness (Table 3).