weir3a5.sharpcrest() the procedures of Hulsing, Harry, 1967, Measurement of peak discharge at dams by indirect methods: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 3, Chapter A5, 29 p., http://pubs.usgs.gov/twri/twri3-a5/NA is the empty set and will error out.
weir.sharpcrest(..., type=c("TWRI3A5", NA))data.frame() is returned.
weir3a5.sharpcrest