The Issue: Most of the Lower Duwamish River Valley in Seattle, Washington, is less than 20 feet above sea level; consequently, the river valley is prone to flooding during high tides, extreme rainfall, and high streamflow. In addition, groundwater inundation—localized coastal flooding due to a rise of the groundwater table with global sea-level rise—may compound flooding issues in the area. The King County Wastewater Treatment Division (WTD) operates and maintains an infrastructure system that is primarily on the land surface or buried in the shallow subsurface. Owing to the likelihood of a future rise in the groundwater table due to sea-level rise, WTD infrastructure may be at risk to groundwater inundation.
How USGS will help: The objective of the study is to develop a detailed hydrogeologic conceptual model and groundwater budget for the Lower Duwamish River Valley. This study will establish the framework necessary to construct a numerical groundwater model that could be used to simulate the effects of hydrologic conditions such as sea-level rise, tidal events, flooding events, and rainstorms on the groundwater table and the distribution of salinity in the groundwater system.
Problem: Most of the Lower Duwamish River Valley in Seattle, Washington, is less than 20 feet above sea level; consequently, the river valley is prone to flooding during high tides, extreme rainfall, and high streamflow. In addition, groundwater inundation—localized coastal flooding due to a rise of the groundwater table with global sea-level rise—may compound flooding issues in the area. The King County Wastewater Treatment Division (WTD) operates and maintains an infrastructure system that is primarily on the land surface or buried in the shallow subsurface. Owing to the likelihood of a future rise in the groundwater table due to sea-level rise, WTD infrastructure may be at risk to groundwater inundation.
Objectives: The objective of the study is to develop a detailed hydrogeologic conceptual model and groundwater budget for the Lower Duwamish River Valley. This study will establish the framework necessary to construct a numerical groundwater model that could be used to simulate the effects of hydrologic conditions such as sea-level rise, tidal events, flooding events, and rainstorms on the groundwater table and the distribution of salinity in the groundwater system.
Relevance and Benefits: Completion of the proposed work will provide foundational information to the WTD—along with water-resource managers and city planners in Seattle—that will inform and direct current and future actions to prepare for global sea-level rise. This study will provide information that advances flood-inundation science and will also improve understanding of the groundwater system that plays a major role in the movement of contaminants to the Lower Duwamish Waterway, a Federal Superfund site.
Approach: To meet the objective of this study, the approach will be split into four primary tasks: (1) well inventory; (2) well-network planning, deployment, monitoring, and analysis; (3) groundwater-budget modeling to estimate groundwater recharge, and (4) development of the hydrogeologic framework. Hydrologic and geologic information from existing studies will be synthesized with new information from drillers’ well logs, groundwater-level measurements (hereafter, water-level measurements), groundwater-salinity measurements, and slug tests conducted at wells.
- Overview
The Issue: Most of the Lower Duwamish River Valley in Seattle, Washington, is less than 20 feet above sea level; consequently, the river valley is prone to flooding during high tides, extreme rainfall, and high streamflow. In addition, groundwater inundation—localized coastal flooding due to a rise of the groundwater table with global sea-level rise—may compound flooding issues in the area. The King County Wastewater Treatment Division (WTD) operates and maintains an infrastructure system that is primarily on the land surface or buried in the shallow subsurface. Owing to the likelihood of a future rise in the groundwater table due to sea-level rise, WTD infrastructure may be at risk to groundwater inundation.
How USGS will help: The objective of the study is to develop a detailed hydrogeologic conceptual model and groundwater budget for the Lower Duwamish River Valley. This study will establish the framework necessary to construct a numerical groundwater model that could be used to simulate the effects of hydrologic conditions such as sea-level rise, tidal events, flooding events, and rainstorms on the groundwater table and the distribution of salinity in the groundwater system.
Sources/Usage: Public Domain.Hydrogeologic Framework for Lower Duwamish River Valley, Washington Problem: Most of the Lower Duwamish River Valley in Seattle, Washington, is less than 20 feet above sea level; consequently, the river valley is prone to flooding during high tides, extreme rainfall, and high streamflow. In addition, groundwater inundation—localized coastal flooding due to a rise of the groundwater table with global sea-level rise—may compound flooding issues in the area. The King County Wastewater Treatment Division (WTD) operates and maintains an infrastructure system that is primarily on the land surface or buried in the shallow subsurface. Owing to the likelihood of a future rise in the groundwater table due to sea-level rise, WTD infrastructure may be at risk to groundwater inundation.
Objectives: The objective of the study is to develop a detailed hydrogeologic conceptual model and groundwater budget for the Lower Duwamish River Valley. This study will establish the framework necessary to construct a numerical groundwater model that could be used to simulate the effects of hydrologic conditions such as sea-level rise, tidal events, flooding events, and rainstorms on the groundwater table and the distribution of salinity in the groundwater system.
Relevance and Benefits: Completion of the proposed work will provide foundational information to the WTD—along with water-resource managers and city planners in Seattle—that will inform and direct current and future actions to prepare for global sea-level rise. This study will provide information that advances flood-inundation science and will also improve understanding of the groundwater system that plays a major role in the movement of contaminants to the Lower Duwamish Waterway, a Federal Superfund site.
Approach: To meet the objective of this study, the approach will be split into four primary tasks: (1) well inventory; (2) well-network planning, deployment, monitoring, and analysis; (3) groundwater-budget modeling to estimate groundwater recharge, and (4) development of the hydrogeologic framework. Hydrologic and geologic information from existing studies will be synthesized with new information from drillers’ well logs, groundwater-level measurements (hereafter, water-level measurements), groundwater-salinity measurements, and slug tests conducted at wells.
- Partners