Numerous of sustainable development related challenges are emerging today, e.g. flooding problems. Our group has developed "the flood walk" project since 2010 to convey flood risk knowledge in an authentic context. Considering the limitation of time and space to educate people the flood risk knowledge, we tried to transform the physical flood walk field trip into a Web-based virtual trip. In this study, we aim to examine whether the Web-based flood-walk environment can help participants to achieve the same learning outcome as its authentic counterpart. A total of 65 upper secondary school pupils participated in this study. The results illustrate that a physical experience is irreplaceable, and the importance of providing "physical experiences" for learners in both formal and informal education needs to be emphasised.