Which mathematical representation for geomorphic processes best matches a given study site? How can we test agreement or disagreement between models and reality? How should we determine what values to use for model parameters?
Three papers representing the culmination of ~four years of work (led by the indefatigable Katy Barnhart of CU Boulder) on these problems were just published in JGR: Earth Surface. Find part 1, part 2, and part 3.