Investigating the impact of watershed land cover change on the hydrometric state of the Upper Kennebecasis River

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University of New Brunswick


Along with the increase in frequency and seriousness of flooding happening globally, southern New Brunswick is no exception. The Upper Kennebecasis River has seen increased flooding due to higher water levels and discharges. This study aims to determine a link between high water levels and discharges and land-use changes in the Upper Kennebecasis River watershed from 1985-2019. Trends in hydrometric and meteorological data were analyzed using the Mann-Kendall test. Significant increasing trends were as follows: winter and fall maximum discharge; January, November, December, and winter average discharge; annual peak water level; winter and fall maximum water level; and January, February, and December average water level. Only two trends were found in the meteorological data: the average winter temperature and the December precipitation. Annual precipitation remained unchanged during the study period, which allows us to conclude that increased precipitation is not the cause of the increased flooding. Land-use changes were determined by comparing land-use maps established for 1984 and 2019 from the Random Forest Classifier using a combination of Landsat imagery and LiDAR-based topographical variables. The overall classification accuracies for the 1984 and 2019 images were 98.6% and 94.1% respectfully. From 1984-2019, there was a 20% TWA loss in mixedwood, however, there was a 20% TWA increase in softwood and shrubland. The change of the mixed-wood forests to softwood plantation and shrubland areas (which corresponded to regeneration areas) may be the cause of the increase in water level and discharge in the Upper Kennebecasis River watershed. Keywords: Land Cover Change, Landsat-8 OLI, Landsat-5 TM, runoff, flooding, Random Forest