research_interests

                     Rip Currents in the Great Lakes
          Characterization, Forecast, and Warning

Rip currents are shore-normal, rapid seaward flows that originate in the surf zone. As a hidden but lethal hazard at Great Lakes beaches, rip currents can quickly sweep swimmers away from the shore out to the open, deep water. It has been estimated by the Great Lakes Current Incident Database that every summer an average 12 fatalities and 26 rescues are related to rip currents during from 2002 to 2012. Rip currents sometimes are incorrectly referred as “undertows” or “rip tides”; however, those are three different phenomena. Undertow is the backwash of breaking waves and in general a weak flow. On the other hand, rip tides are strong offshore currents caused by the constricted tidal flow through barrier beaches. In comparison, rip currents are strong, non-periodical, discretely located, and more dangerous than the other two types of offshore currents. Rip currents are in general caused by spatial difference in wave breaking along the shoreline; however, the mechanism for generation of rip current can be complicated and varies on a beach-to-beach basis. To improve beach hazard rip-current warning, we will develop an Integrated Nowcast (real-time) Observation and Forecast (future) Operation System (INFOS) and applying the INFOS at three rip-current prone beaches through coordination, communication, and community outreach and education. The three beaches, (i) Park Point Beach, Duluth, MN, (ii) Mckinley and Bradford Beach, Milwaukee, WI, and (iii) North Beach, Port Washington, WI, are identified as high occurrence of bar-gap, headland, and structured-induced rip currents, respectively. The proposed project is an integrated and collaborative effort among partners: UW-Madison, Minnesota/Wisconsin Sea Grants, Wisconsin Coastal Management Program, National Weather Service at Duluth and Milwaukee/Sullivan, City of Duluth, Milwaukee County, and City of Port Washington, NOAA-NOS and Great Lakes Environmental Research Laboratory. Several news related to the INFOS-rip current project can be accessed here.

4 drown, 3 missing in Lake Michigan Unexpected rip currents induced by meteotsunamis

Flash rips under small wave and low water level fluctuations Drowning incident events vs hydrodynamic & storm conditions

INFOS-Port Washington Real-Time Rip Current Warning

Three situations of hidden flash rip occurrences

Further Information can be found in the following links:

Publications:

Liu, Y. and Wu, C.H. 2022. Drowning incidents and conditions due to hidden flash rips in Lake Michigan, Science of the Total Environment, In Press, doi.org/10.1016/j.scitotenv.2022.154314
Liu, Y. and Wu, C.H. 2022. Rip currents near coastal structures in Lake Michigan: characterization and assessment for warnings. J. of Great Lakes Research., In Press. https://doi.org/10.1016/j.jglr.2022.03.001.
Liu, Y and Wu, C.H., 2019. Lifeguarding Operational Camera Kiosk System (LOCKS) for Flash Rip Warning: Development and Application, Coastal Engineering, doi:10.1016/j.coastaleng.2019.103537
Linares Á., Wu, C.H., Bechle, A.D., Anderson, E.J., and Kristovich, DAR. 2019, Unexpected rip currents induced by a meteotsunami, Scientific Reports, 9(1), 2105, doi:10.1038/s41598-019-38716-2.