Estimating Impacts of Hurricanes on Forest Hydrological Processes Using HAWQS Model and Multivariate Statistics

Hurricanes are disastrous events to social activities and natural processes in coastal regions. This study is to ascertain the impacts of multiple hurricanes on hydrological processes using Hydrologic and Water Quality System (HAWQS) model and multivariate statistics (i.e., principal component analysis (PCA) and principal factor analysis (PFA)). Five hurricanes, with tracks through the forest dominated Apalachicola watershed of Florida panhandle from 1966 to 2018 (52 years), were selected in this study. The hydrological processes used for our analysis included rainfall, potential evapotranspiration (PET), evapotranspiration (ET), soil water percolation, surface runoff, stream discharge, groundwater discharge, and water yield (WYLD). The HAWQS simulation results showed that daily stream discharge during the hurricanes increased with daily rainfall and occurred because rainfall is a major driving force for stream discharge. A 1.9-fold increase in daily rainfall would result in an increase in daily stream discharge of more than 3.2 times. However, the amount of rainfall was not necessarily proportional to the amount of stream discharge during the hurricanes. The preceded rainfall conditions also played an important role in stream discharge during the hurricanes. The designated hurricane category was not highly related to the rates of daily rainfall, surface runoff, WYLD, and stream discharge during the hurricanes. The amount of surface runoff was always lower than that of WYLD during hurricanes and occurred because WYLD includes not only surface runoff but also baseflow to reaches and shallow groundwater discharge to reaches. Based on the component loadings of the PCA, the hurricanes increased the rates of rainfall, percolation, runoff, groundwater recharge, WYLD, and stream discharge but decreased the rates of the PET and ET. The PFA showed that the rainfall, PET, ET, and stream discharge were highly affected while the percolation, runoff, groundwater discharge and WYLD were relatively less affected by the hurricanes.