Changes in cold region flood regimes inferred from long‐record reference gauging stations

Abstract

Variability and nonstationarity in flood regimes of cold regions are examined using data from hydrometric reference streamflow gauging stations from 27 natural watersheds in Canada and adjacent areas of the United States. Choosing stations from reference networks with nearly 100 years of data allows for the investigation of changes that span several phases of some of the atmospheric drivers that may influence flood behavior. The reference hydrologic networks include only stations considered to have good quality data and were screened to avoid the influences of regulation, diversions, or land use change. Changes and variations in flood regimes are complex and require a multifaceted approach to properly characterize the types of changes that have occurred and are likely to occur in the future. Peaks over threshold (POT) data are extracted from daily flow data for each watershed, and changes to the magnitude, timing, frequency, volume, and duration of threshold exceedences are investigated. Seasonal statistics are used to explore changes in the nature of the flood regime based on changes in the timing of flood threshold exceedences. A variety of measures are developed to infer flood regime shifts including from a nival regime to a mixed regime and a mixed regime to a more pluvial‐dominated regime. The flood regime at many of the watersheds demonstrates increased prominence of rainfall floods and decreased prevalence of snowmelt contributions to flood responses. While some individual stations show a relationship between flood variables and climate indices, these relationships are generally weak.

Climate-driven variability in the occurrence of major floods across North America and Europe

“…If we had focused on a specific area of the west coast of North America, a different result with regard to the PDO may have occurred. Burn and Whitfield (2017) considered century long records from a small number of references sites in Canada and the United States and suggested the differences between their PDO results, and those of others, can be explained by the longer time period examined and the exclusive use of reference hydrologic network sites, where the effects of non-climatic factors have been minimized. Merz et al (2012) argue that properly detecting changes in flooding over time requires a stricter approach than many previous studies have used.…”

Pooled frequency analysis for intensity–duration–frequency curve estimation

“…In the present study, nonstationary rainfall stations across Canada are identified by a trend analysis based on the block bootstrap Mann-Kendall (BBMK) test (Khaliq, Ouarda, Gachon, Sushama, & St-Hilaire, 2009;Önöz & Bayazit, 2012), which accounts for autocorrelation in rainfall series. The BBMK test has been applied in the past for flood and rainfall trend studies (e.g., Burn & Whitfield, 2017;Sarhadi & Soulis, 2017).…”

Shifting Hydrological Processes in a Canadian Agroforested Catchment due to a Warmer and Wetter Climate

“…Ongoing and future changes in air temperature and the amount and timing of precipitation can have large impacts on the hydrological cycle, such as changes to the quantity, seasonality and timing of streamflow [1][2][3][4][5]. These changes are likely to vary regionally depending on current and future regional climate conditions and catchment characteristics.…”