Preliminary Assessment of Flooding Hazards in the Nooksack River Watershed, Washington State, and its Effect on Water Quality and the Local Shellfish Industry

Flooding in the Nooksack River in northwestern Washington State has been the product of heavy rains occurring between the months of October and March (Nooksack Indian Tribe, 2016). Increasing winter temperatures will decrease the amount of snowfall experienced along the Nooksack River floodplain and Whatcom County and replace it with rainfall. Heavy rainfall and overland flow along the floodplain has the potential to move sediment, organics, and contaminants from the floodplain to the Nooksack River (NOAA, 2015).

To investigate influences on fecal coliforms concentrations in the Nooksack River, the relationship between flood events and fecal coliforms concentrations was analyzed. Conclusions drawn from this relationship then analyzed how increasing temperatures and precipitation would affect the frequency of floods over the next 50 years, and the potential response of the fecal coliform concentrations in Portage Bay. It is expected that flood frequency will increase over the next 50 years. As a result, fecal coliform concentrations in the Nooksack River and Portage Bay will increase.