The 587 mm of rainfall for July was the second highest monthly precipitation since records began in 1981. The highest recorded was 639 mm for July 2013. Although the maximum flood stage and peak discharge was not particularly high last month (1.26 m, 30 m3/s at 11:30 on 24 July), the hydrograph shows multiple peaks around 1.0-1.2 m stage.
Comparing the measured discharge with the estimated discharge from the stage-rating curve, we find a discrepancy of about 25%. The discharge is 25% higher than we expect from using the current stage-rating curve, indicating degradation of the channel during the floods of 24 July. The removal of the sediment deposited from the tributary channel earlier in July is also evidence of likely channel degradation. Further discharge measurements are needed in the near future to confirm this change in the stage-rating curve.
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| Young hydrologist - first discharge measurement (Grade 4) |
