Discharge estimation in a backwater affected meandering river

Abstract

Abstract. Variable effects of backwaters complicate the development of rating curves at hydrometric measurement stations. In areas influenced by backwater, single-parameter rating curve techniques are often inapplicable. To overcome this, several authors have advocated the use of an additional downstream level gauge to estimate the longitudinal surface level gradient, but this is cumbersome in a lowland meandering river with considerable transverse surface level gradients. Recent developments allow river flow to be continuously monitored through velocity measurements with an acoustic Doppler current profiler (H-ADCP), deployed horizontally at a river bank. This approach was adopted to obtain continuous discharge estimates at a cross-section in the River Mahakam at a station located about 300 km upstream of the river mouth in the Mahakam delta. The discharge station represents an area influenced by variable backwater effects from lakes, tributaries and floodplain ponds, and by tides. We applied both the standard index velocity method and a recently developed methodology to obtain a continuous time-series of discharge from the H-ADCP data. Measurements with a boat-mounted ADCP were used for calibration and validation of the model to translate H-ADCP velocity to discharge. As a comparison with conventional discharge estimation techniques, a stage-discharge relation using Jones formula was developed. The discharge rate at the station exceeded 3250 m 3 s −1 . Discharge series from a traditional stage-discharge relation did not capture the overall discharge dynamics, as inferred from H-ADCP data. For a specific river stage, the discharge range could be as high as 2000 m 3 s −1 , which is far beyond what could be explained from kinematic wave dynamics. Backwater effects from lakes were shown to be significant, whereas interaction of the river flow with tides may impact discharge variation in Correspondence to: H. Hidayat (hidayat.hidayat@wur.nl) the fortnightly frequency band. Fortnightly tides cannot easily be isolated from river discharge variation, which features similar periodicities.

Dissolved oxygen and water temperature dynamics in lowland rivers over various timescales

“…The other most classical example is the hysteretic relation between water level and discharge during backwater events (Herschy, 2009;Hidayat et al, 2011). As has been well documented, single-parameter rating curves developed for particular hydrometric stations fail to reflect the real discharge under unsteady flow occurring during backwaters or flood propagation waves (Hidayat et al, 2011;Mrokowska et al, 2014;Petersen-Overleir, 2006;Rowiński et al, 2000). To compare, the studies of Moog and Whiting (1998) have shown the hysteresis between river discharge and bed load transport, whereas Williams (1989) reported hysteresis between discharge and sediment concentration rates during flood events.…”

“…For example, it was applied in conceptual models such as linear reservoirs (O'Kane, 2005). The other most classical example is the hysteretic relation between water level and discharge during backwater events (Herschy, 2009;Hidayat et al, 2011). As has been well documented, single-parameter rating curves developed for particular hydrometric stations fail to reflect the real discharge under unsteady flow occurring during backwaters or flood propagation waves (Hidayat et al, 2011;Mrokowska et al, 2014;Petersen-Overleir, 2006;Rowiński et al, 2000).…”

Flood occurrence mapping of the middle Mahakam lowland area using satellite radar

“…They have a function as a buffer by storing water during the high flow conditions, and releasing it during low flows. Lake filling and emptying mechanisms play a role to shave water level peaks downstream of the Mahakam lakes area (Hidayat et al, 2011b). The MMA is also surrounded by peatland, as part of the Kutai lowland spreading over an area of 35 km NW-SE by 130 km SW-NE, with elevations of around sea level in the Mahakam River to ca.…”

Anatomy of simultaneous flood peaks at a lowland confluence

“…However, if most precipitation would be concentrated further upstream in the Meuse basin, the difference in 15 travel time would merely increase by about two days (Figure 12). Two days extra travel time would still result in simultaneous cause backwater effects apparent as hysteresis in a rating curve cannot be readily accounted for (Figure 11) (Hidayat et al, 2011(Hidayat et al, , 2016. During the highest discharge waves, backwater variation shows to be most severe.…”