Fourth, In-Person Technical Meeting of International Working Group Developing Guidelines for Use of Natural and Nature-Based Features: From March 5th – 9th, more than 40 people participated in the fourth, in-person meeting of the International Working Group, being led by USACE, that is developing guidelines for use of Natural and Nature-Based Features (NNBF). The meeting was hosted by Rijkswaterstaat (RWS), Ministry of Infrastructure and Water, and Deltares in Delft, Netherlands. Collectively, attendees at this meeting represented 4 different countries and more than 20 different organizations. Dr. Maarten Smits, CEO Deltares; Dr. Cees Brandsen, Managing Director RWS-Water, Transport and the Environment; Dr. Hans Pietersen, Senior Advisor for International Affairs, RWS; and Dr. Todd Bridges, Senior Research Scientist, ERDC provided opening remarks to the group. This 5-day, in-person meeting was an opportunity to review project progress, advance the development of chapters that will comprise the NNBF Guidelines Document, and select NNBF Case Studies that will illustrate key concepts within applicable chapters. The meeting also provided valuable input through presentations provided by USACE, Deltares and RWS representatives. RWS also arranged site visits for participants to inspect riverine/fluvial or coastal NNBF projects that were constructed in the Netherlands.