CLIMATIC AND MORPHOLOGIC RELATIONSHIPS OF RIVERS - IMPLICATIONS OF SEA-LEVEL FLUCTUATIONS ON RIVER LOADS

The characteristics of 279 rivers that discharge into the world oceans are analyzed in terms of their basin hydrology (river discharge), mor phometry (basin slope and area, river length, extension of the contine ntal shelf seaward of the river mouth), and climate (precipitation). S tatistically reliable relationships are found between discharge and ba sin area, and between sediment load and a combined function of basin a rea and slope. These functions are used to demonstrate how river hydro logic features would be strongly influenced by sea-level fluctuations, particularly under the influence of continental shelf emergence. A fa ll in sea level toward a glacio-eustatic lowstand would induce the mer ging of rivers on the subaerial continental shelf, thereby allowing gi ant rivers to form. For example, rivers of western Europe would reorga nize themselves into two or three very large rivers. Sediment concentr ation carried by these mega-rivers would decrease, and thus the number of hyperpycnal plumes generated at river mouths would be reduced. The re would, however, be a strong increase in global sediment delivery an d thus in the frequency of undrained delta-front failures because of b oth the progressive concentration of depocenters at the mouths of gian t rivers and delta migration toward the shelf breaks. The global incre ase of sedimentation rate should then be emphasized at giant river mou ths. Associated with a global increase of hypsometry would be a signif icant increase in the frequency and volume of turbidity currents, sinc e high slopes facilitate flow acceleration and slope erosion.