A Global-Scale Distributed Geomorphologic Product
Friday, 18 December 2015
Poster Hall (Moscone South)
In response to the vital role of geomorphological analysis in natural hazards study, geomorphology, distributed hydrology and other related disciplines, we present the first global basin morphometric product of 30 characteristics, 9 archived elementary including stream order, stream number, stream length, basin relief, basin length, basin perimeter, maximal flow length, down valley length and overland flow length, and 21 derivable from these elementary morphometric characteristics. As a distributed product, characteristics of basins discharging to every grid-cell of the global earth surface are computed at 1km resolution strictly following their definitions. We introduce in this paper an efficient framework to reduce the algorithm complexity to O(N), which results in efficiency improvement in the order of 50-100 times the traditional way. We find that, spatially, 1) the relief ratio reaches its peak values along both sides of the ridges; 2) the fitness ratio of the main stream value often has a sharp decrease at the joint of large tributaries; statistically, 3) only the basin relief exhibits strong discrepancy of distribution among different continents while all others show unexpected homogeneity of distribution in spite of the size (number of cells) difference of continents; 4) the distributions of the main flow length/down valley length and basin length/basin perimeter resemble each other respectively; and 5) the distributions of the two pairs are quite different thus neither the main flow length nor down valley length should be used as substitutions of the basin length as done by some previous studies.