Combining satellite imagery with forest inventory data to assess damage severity following a major blowdown event in northern Minnesota, USA

Effects of a catastrophic blowdown event in northern Minnesota, USA were assessed using field inventory data, aerial sketch maps and satellite image data processed through the North American Forest Dynamics programme. Estimates were produced for forest area and net volume per unit area of live trees pre- and post-disturbance, and for changes in volume per unit area and total volume resulting from disturbance. Satellite image-based estimates of blowdown area were similar to estimates derived from inventory plots and aerial sketch maps. Overall accuracy of the image-based damage classification was over 90%. Compared to field inventory estimates, image-based estimates of post-blowdown mean volume per unit area were similar, but estimates of total volume loss were substantially larger, although inaccessibility of the most severely damaged inventory plots may have depressed the inventory-based estimate. This represents the first application of state model differencing to storm damage assessment. The image-based procedure can be applied to historical archives of satellite imagery and does not require pre-disturbance field inventory data.