[2] The Niawiakum River originates in the hills of the southwestern part of Washington.

The lower half of the Niawiakum River is a broad estuary and tidal marshland.

The river estuary and its tidal salt marsh vegetation is among the highest quality of the entire Washington and Oregon coasts.

[7] The lower Niawiakum River shows traces of the 1700 Cascadia earthquake and associated tsunami.

Field trips to the river have been part of a Certificate Program in Tsunami Science and Preparedness offered by the University of Washington (UW) in cooperation with the National Oceanic and Atmospheric Administration (NOAA).