How do sand dunes migrate? a. sand moves up the steeper side of the dune by saltation and accumulates just beyond the crest of the dune. as more sand collects, the slope steepens, and some of the sand slides down the slip face side of the dune. b. sand moves up the slip face of the dune by saltation and accumulates just beyond the crest of the dune. as more sand collects, the slope steepens, and some of the sand slides down the leeward of the dune. c. sand moves up the gentler side of the dune by saltation and accumulates just beyond the crest of the dune. as more sand collects, the slope steepens, and some of the sand slides down the slip face of the dune. d. sand moves up the leeward slope of the dune by saltation and accumulates just beyond the crest of the dune. as more sand collects, the slope steepens, and some of the sand slides down the slip face of the dune. e. sand moves up the windward side of the dune by rolling and accumulates just beyond the crest of the dune. as more sand collects, the slope steepens, and some of the sand slides down the slip face of the dune.