PacTrans: Estimating Future Flood Frequency and Magnitude in Basins Affected by Glacier Wastage

AUTC project number: S16806


Anna Liljedahl

  • PacTrans
  • Start Date: Jun 1, 2012
  • End Date: Nov 1, 2013

Project Summary

Infrastructure, such as bridge crossings, requires informed structural designs in order to be effective and reliable for decades. A typical bridge is intended to operate for 75 years or more, a period of time that is anticipated to exhibit a warming climate and consequently, hydrologic changes (IPCC 2007). An understanding of present and future possible hydrologic conditions is necessary to avoid damage to critical infrastructure and costly disruptions to Alaska's transportation network. Several major roads in Alaska cross streams that represent runoff from glacierized basins. Projectionsof glacier wastage under a warming climate show initial increases in glacier runoff (Hock et al. 2005, Radic and Hock, 2011), which can be substantial and exceed all other runoff components in a watershed (Adalgeirsdottir et al. 2006). Accordingly, flood events may become more frequent and more severe. Changes in the proportion of streamflow derived from glacial runoff will affect physical properties of streams such as overflow and stream reorganization (Hood and Berner 2009), which in turn, could have significant impacts on Alaska's infrastructure. Engineering design criteria continues to rely heavily on the assumption that historical hydrologic conditions will persist. The validity of this claim for Alaska is weak, given the multitude of scientific literature that proposes altered hydroclimatology in coming decades. Efforts in assessing the impacts of climate variability and change on flood frequency and magnitude in Alaska has included statistical techniques confirming the importance of the Pacific Decadal Oscillation (Neal et al. 2002, Hodgkins 2009) and highlighted the constraints of limited runoff records in identifying trends (Tidwell 2010). An application of a physically-based hydrologic model, which is first validated in order to quantify its uncertainty, has the potential to extend statistical analyses into the future and ultimately inform management decisions. The limited road network of Alaska is not only distributed across an enormous area but also over a multitude of climate regimes. Accordingly we may expect a broad range of hydrologic responses to anticipated climate warming and anticipate the need for differing solutions to adequately manage risk and balance construction, maintenance and flood damage costs. We propose to analyze four watersheds, each representing differing climates, by combining field measurements and computational modeling to improve estimates of future peak flow frequency and magnitude.