Hydroclimatic aspects of ice jam flooding near Perth-Andover, New Brunswick

Abstract

Major ice jam floods occurred along the Saint John River at Perth-Andover, New Brunswick, in 1976, 1987, 1993, 2009, and 2012. These floods have been devastating and resulted in relocation or demolition of many buildings in affected areas of the community. The purpose of this paper is to review ice processes along the Saint John River from Grand Falls to Beechwood Dam and their relevance to the ice-related problems that have occurred in Perth-Andover. The HEC-RAS program was chosen for ice jam flood stage computations, and cross-sectional, roughness and flow information entered to create a model of the study reach. The model was calibrated using field data obtained on 31 March 2000 along an ice jam in the Perth-Andover area. Model applications resulted in stage-discharge relationships for ice jams of different lengths and locations within the study stretch (Beechwood Dam to Grand Falls). These relationships indicate that ice jams can cause flooding at Perth-Andover, even with moderate spring breakup flows. The variation of ice jamming potential along the study stretch, and its relation to reservoir bathymetry and slope, are discussed. The increase in the number and severity of ice jam floods that have affected Perth-Andover may have resulted from changes in infrastructure and climate that have occurred since the 1950s. Local ice problems are likely to be aggravated over the next few decades but tempered in the longer term if the climate continues to change according to current projections.