WHAT A FLOOD WILL DO

MII/LIONS OF TONS OF &AND ~ .'. .'. SHIFTED. . '

Interesting data as the' effect of a flood in the Wairoa River on .May 17, 18, and 19, have boen compiled by Mr. I.eslio H.- Reynolds,-engineer to'the Wairoa Harbour Board. An examination of tho water passing down tho rivor during the flood showed .that'it contained 1 Jib. of dry silt per cubic foot of water. Tbo area of tho basin of tho Wairoa River is taken:as 1400 square miles. Rainfall records have been received from seven stations, in or near tho watershed, tho average fall being 14.55 inches, which is probably sliglitly less than the averages within the waterkliod. Reckoning from the above, tho. total rainfall was 47,150,000,000 cubio feet, and considering .tlio saturated Etate of the ground previous to the storm, 1 it is safo to assume that practically the whole of the water ran off ot once, Tho amount estimated to flow in the river through tho town from' measurements mado during the flood vas 43,200,000,000 cubic foet, about ton per cent, less than the ahovo quoted figure. This gives a silt discharge of 30,840,000 tons of dry ailt,. equal to about ten square rniles three font deep. At its height tho river was running at fifteen million cubic foet per minute.