Abstract |
An analysis of 240 flood hydrographs of 29 small watersheds on Oahu shows some unique hydrologic characteristics. Many of these watersheds are small, some measuring less than 5 square miles, and they have extreme variations in rainfall. Between 4 and 15 single-peak hydrographs were collected for each watershed. The Instantaneous Unit Hydrograph was more adaptable for ocean island conditions such as the Hawaiian Islands, and each individual watershed could be treated by computers. In analyzing these flood hydrographs, hydrologic characteristics such as small area, flush peak, short time to peak, and recession constant, were calculated. Time to peak, which is affected by a combination of storm and watershed characteristics, varied within short distances, as well as between basins. Average rainfall duration ranged from a minimum of 5 minutes to a maximum of 1 hour over a 100 year period. A good correlation was found to exist between effective rainfall duration and the watershed area. (Author) |