* 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).