Preventing damages from flooding is critically important for city managers and planners.Efforts in protecting infrastructure from flooding are often coupled with building hydrologicmodels to provide predictions of what is likely to happen during storm events. As land usechanges, these models must be updated, which is more challenging with sophisticated models. Ateam of researchers from universities in Utah and Wyoming have been developing tools forwater management in the Intermountain West as part of a collaborative NSF research grantcalled CI-WATER. In particular, a free and open source web platform called Tethys has beendeveloped to support the development and hosting of hydrologic web applications. Tethys wasused to develop a prototype application that uses a GSSHA runoff model and allows users tochange land-use inputs to simulate the impact on a watershed for any type of land use change.The application also provides a method to run the edited model and produces a comparisonreport of before-and-after runoff and water depth as part of a decision-support framework.