Tides in Puget Sound are of the mixed type with two high and two low tides each tidal day. These are called Higher High Water (HHW), Lower Low Water (LLW), Lower High Water (LHW), and Higher Low Water (HLW). The configuration of basins, sills, and interconnections cause the tidal range to increase within Puget Sound. The difference in height between the Higher High Water and the Lower Low Water averages about feet ( m) at Port Townsend on Admiralty Inlet, but increases to about feet ( m) at Olympia, the southern end of Puget Sound. 
The Puget Sound River History Project studies the historical landscape of Puget Sound's lowland rivers and estuaries as a dynamically linked geophysical, ecological, and human system. The historical emphasis is on conditions at the time of earliest Euro-American settlement in the mid-19th century, but also includes the landscape's post-glacial, Holocene (10,000 yrs BP) evolution and the last century and a half of change. We undertake interdisciplinary research that integrates archival investigations, field studies, and the tools of geographic information systems and remote sensing. We also apply the results to, and make data available for, regional problems of resource management, restoration and planning.