Percent surface water estimation from MODIS BRDF 16-day image composites

Four models for deriving percent surface water estimates were developed for use with MODIS16-day Bidirectional Reflectance Distribution Function (BRDF) corrected composite images. The models allow intra-annual surface water estimates to be produced with 1 km spatial resolution and an 8-day temporal resolution when applied to image composites from sensors on both the Aqua and Terra platforms. The surface water models are conceptually simple, relying on widely used indices (NDVI, NDWI, and tasseled cap), but computationally intensive. The models differ in the time and effort required to produce or acquire the inputs necessary for model training. The models were applied and tested in Yukon Flats National Wildlife Refuge, an area with varied surface water types including ponds, fens, and the Yukon River and its tributaries. Resulting accuracies peaked with an R2 of approximately 0.625, and model accuracies were higher for pixels with higher percentages of water.

Research highlights
► A method for estimating per-pixel percent surface water every 8 days using MODIS data.
► Eight models are tested and compared in Yukon Flats National Wildlife Refuge, Alaska.
► Temporally and spatially varying models produce the most accurate results.