Across the globe, climate change is projected to affect the quantity, quality, and timing of freshwater availability. In western North America, there has been a shift toward earlier spring runoff and more winter precipitation as rain. This raises questions about the need for increased water storage to mitigate both floods and droughts. Some water managers have identified natural storage structures as valuable tools for increasing resiliency to these climate change impacts. However, identifying adequate sites and quantifying the storage potential of natural structures is a key challenge. This study addresses the need for a method for identifying and estimating floodplain water storage capacity in a manner that can be used by water planners through the development of a model that uses open-source geospatial data. This model was used to identify and estimate the storage capacity of a 0.33 km2 floodplain segment in eastern Montana, USA. The result is a range of storage capacities under eight natural water storage conditions, ranging from 900 m3 for small floods to 321,300 m3 for large floods. Incorporating additional hydraulic inputs, stakeholder needs, and stakeholder perceptions of natural storage into this process can help address more complex questions about using natural storage structures as ecosystem-based climate change adaptation strategies.