Abstract

Rainfall index has become the most important index in all rainfall-induced natural disaster. Rainfall intensity in 5 or 10 minutes, accumulated rainfall amount in 1 hour to 24 hours are most used index. The dominate rainfall data comes from wide distributed traditional rainfall gauge. Although rainfall radars are used and considered to be better than traditional rainfall gauge, but Radar data still needs rain gauge data for calibration and justification. The dominant type of rain gauge is the ticking bucket rain gauge (TBR). This research derived the error and accuracy of TBR. The equations of motion were derived through the conservation of linear momentum and angular momentum. An initial value problem was obtained, and the input rainfall was calculated using the 4th order Runge-Kutta method. The result of the theory was compared with ISO certified indoor experiments with an error less than 1%. Then the result is compared with field measurement. It is found that high-intensity rainfall is usually underestimated from readings of tipping bucket rain gauge. The actual rainfall is greater than the reading with a surprising 40% error when rainfall intensity reaches 600mm/hr. But the error is not linear and is greater for high-intensity rainfall.

Keywords: Tipping bucket rain gauge; High rainfall intensity