Community members are invited to attend a virtual public workshop from noon to 1:10 p.m. today to discuss how to reduce risks of catastrophic flooding in Honolulu’s Ala Wai watershed.

It will be the first of four workshops, with the others scheduled for the same time on April 8, 14 and 22. The events will be hosted by the U.S. Army Corps of Engineers and the City and County of Honolulu, which are partners in the process of gathering ideas for an Ala Wai Canal Flood Risk Management General Reevaluation Study to be conducted by the corps.

The first three workshops will focus on potential solutions within the watershed’s major sub-basins: Today’s will explore Makiki and Palolo valleys; April 8 will address Manoa Valley; and April 14 will examine the Ala Wai Canal and lower watershed.

The last workshop, April 22, will comprise “continued discussions,” according to the city website for the project, honolulu.gov/ alawai.

The Ala Wai watershed encompasses 19 square miles, or 12,064 acres, flaring down and out from the topmost ridges of the Koolau range to the waters of Mamala Bay at Waikiki, as well as Ala Moana Regional Park and Kewalo Basin.

The Makiki, Manoa and Palolo streams flow into the 2-mile-long Ala Wai Canal, constructed during the 1920s to divert stream waters that once flowed to the ocean through the former wetlands of Waikiki, where Native Hawaiians cultivated kalo and fishponds.

This permitted the draining and development of Waikiki, the threat to whose economic engine, as well as the entire watershed’s 200,000 residents, has motivated decades of flood risk abatement studies and proposals.

Previous proposals, which included upstream catchment reservoirs and walls bracketing the canal, have been set aside.

A Management Measure Tracking Spreadsheet on the project website contains 202 suggestions from the public. Several recommend removing invasive plants and concrete channelizations that increase runoff in streams, and instead slowing and absorbing stream flow by channeling their waters through kalo loi and fishponds.

To view the spreadsheet, submit comments or join the workshops, go to honolulu.gov/alawai and click on the links provided.