Wahrhaftig made significant scientific contributions to the field of geology; his work is credited with inspiring the research of many colleagues and students. He was known for his systematic and meticulous field observations. His 1959 paper on Alaskan rock glaciers (co-authored with Allan Cox) inspired a world-wide surge in research on rock glaciers. Wahrhaftig's 1965 paper "Stepped Topography of the Southern Sierra Nevada" was awarded the Geological Society of America (GSA) Kirk Bryan Award. He was one of the first Bay Area scientists to bring the role of plate tectonics in causing earthquakes to public awareness. He was also a pioneer in applying geological science to environmental problems, with a particular focus on forest management practices (e.g., effects of logging on soil erosion). He was appointed to the California Board of Forestry in 1975, where he advocated for forest practices legislation that took a long-term perspective on geomorphological effects of forest management.