REVISITING THE HYPSOMETRIC CURVE AS AN INDICATOR OF FORM AND PROCESS IN TRANSPORT-LIMITED CATCHMENT

Hypsometry has historically been used as an indicator of geomorphic fo rm of catchments and landforms, Yet there has been litle work aimed at relating hypsometry to landform process and scale. This paper uses th e SIBERIA catchment evolution model to explore linkages between catchm ent process and hypsometry. SIBERIA generates results that are qualita tively and quantitatively similar to observed hypsometric curves for p hysically realistic parameters, However, we show that not only does th e hypsometry reflect landscape runoff and erosion process, but it is s trongly dependent on channel network and catchment geometry. We show t hat the width to length ratio of the catchment has a significant influ ence on the shape of the hypsometric curve, though little on the hypso metric integral. For landforms dominated by fluvial sediment transport , the classic Strahler 'mature' hypsometric curve is only generated fo r catchments with roughly equal width and length. Narrow catchments sh ow a hypsometric curve more similar to Strahler's 'monadnock' form. Fo r landscapes dominated by diffusive transport, the simulated hypsometr ic curve is concave-down everywhere, this being consistent with curves reported for some example catchments in France. Because the transitio n between diffusive dominance to fluvial is scale-dependent, with larg er catchments exhibiting greater fluvial dominance, then the hypsometr ic curve is a scale-dependent descriptor of landforms. Experimental re sults for simulated landforms from a small-scale rainfall-erosion simu lator are reported. It is shown that SIBERIA yields satisfactory fits to the data, confirming its ability to predict the form of the hypsome tric curve from a simple model of geomorphic processes. (C) 1998 John Wiley gr Sons, Ltd.