Author(s): Shojun Arai; Taichi Tebakari; Takashi Kitsuda; Yoriko Yoshikawa; Yukihiro Sasakawa
Linked Author(s):
Keywords: ADCP; Uncertainty; Mooring boat; Pitching; Rolling
Abstract: In recent years, ADCP (Acoustic Doppler Current Profiler) has been used in various ways along with the advancement of river flow observation. However, the uncertainty in ADCP observations is not completely clear. The purpose of this study is to evaluate the influence of moored boats used in ADCP on the flow velocity, and to clarify the uncertainty of moored boats give to observed flow velocity values. The observation point of thi s research is Shinano River, a first-class river in Nigata Prefecture, Japan. The Shinano River has the characteristics of large discharge and high flow velocity. We investigated the flow velocity distribution in the Shinano River using ADCP. We used and compared three moored boats: Riverboat (RB), Highspeed Riverboat (HSRB), and 3m Riverboat (3m RB). RB is the cheapest and the usage rate is high. However, when observing high flow velocities, it is recommended to use HSRB or 3m RB. The ADCP’s observed flow velocity values include ADCP specs such as Pitching and Rolling, reflection intensity and correlation, and %Good. The relationship between these elements and the flow velocity value was compared. It was found that the observation accuracy of HSRB and 3m RB is higher than that of RB. In the case of high flow rate, half of the observed flow velocity value were missing for RB. However, the observed flow velocity values of RB are not completely unusable. Analyzes using Relative Frequency and Probability Density Function (PDF) can improve the accuracy observed flow velocity value of RB. From the above, we were able to clarify the uncertainties of mooring boats in observations using RB. By using the analysis method of this study, it was found that even with RB, it is possible to observe with the same accuracy as HSRB and 3m RB.
Year: 2020