FLOW STRUCTURES DETERMINING RIVER LEVEL IN AN ESTUARY

为了了解洪水期间的流量和河水的用途，如农业和水力发电，找到流量和水位之间的正确关系是至关重要的。通常，通过经验H-Q方程假定河流流量由水位给出，其中H为水位（高度），Q为流量，但在干旱期间，将该表达式应用于河口比应用于上游地区变得极其困难。这是因为在潮汐、大气压、风向和风速这四个关键因素的影响下，河面可以取一个大范围的值。在本研究中，试图推导出一种定量估计石kari河河口潮汐、大气压、风向和风速对流量影响的方法，这四个因素显著降低了水位(H)与河流量(Q)之间的相关性。研究发现，潮汐和气压对海平面的影响几乎完全反映在河流水位的波动上。在无风条件下的水位观测数据和稳定的河流流量允许应用纯粹由流量引起的河流上升的经验规则，提供风和河流行为之间关系的定量估计。然后，利用得到的4个因素与河面的定量关系，对某一位置的流量进行估算，结果与实测流量基本一致。这证实了本研究的实际有效性。

It is essential to find the correct relationship between flow rate and river level in order to have information about the flow rate during flood and about uses of the river water like agriculture and hydroelectric generation. Normally, the river flow rate is assumed to be given by the level through the empirical H-Q equation, where H is the water level (height) and Q is the flowrate, but during drought, it becomes extremely more difficult to apply this expression to the estuary than to locations upstream. This is because the river level can take a large range of values under the influence of the four key factors of tide, atmospheric pressure, wind direction and wind speed. In this study, it was attempted to derive a method for quantitative estimation of the effects of tide, atmospheric pressure, wind direction and wind speed on flowrate in the estuary of the Ishikari River, where these four factors dramatically lower the correlation between water level (H) and river flowrate (Q). It was found that the effect of tide and atmospheric pressure on sea level is almost exactly reflected in the fluctuations of river level. Data from observations of river level under windless conditions and steady river flowrate allowed application of empirical rules for river rise due purely to flowrate, providing a quantitative estimate of the relation between wind and river behavior. Next, the flowrate was estimated at a certain location using the obtained quantitative relation between the four factors and river level, and this was found to be nearly identical to the observed flowrate. This confirmed the practical validity of this study.