Using morphometrics to distinguish between debris flow, debris flood and flood (Southern Carpathians, Romania)

Abstract

Debris flows and debris floods are rapid mass movements that occur in rugged mountain areas. The differences between them consist in the quantity of water input, which in turn influences the type of flow. For practical reasons, these two process types should be differentiated because different remedial measures should be applied for planning purpose. Due to the lack of historical data covering a long period of time, a morphometric analysis of the factors that control the flow type was chosen for the present study. Only those morphometric parameters with the most important role were selected. Based on statistical analyses, we noticed that only six parameters have a substantial contribution to debris flow occurrences. These are: Melton number, basin relief ratio, basin length, basin area, fan slope and source area ratio. The results show debris flow basins are characterized by Melton ratio > 0.55, basin relief ratio > 0.4, basin length < 1.7 km and basin area < 1.1 km2, debris flood basins by 0.3 < Melton ratio < 0.55, 0.2 < basin relief ratio < 0.4, 1.7 km < basin length < 5.1 km and 1.1 < basin area < 8.2 km2, while flood basins correspond to values of Melton ratio < 0.3, basin relief ratio < 0.2, basin length > 5.1 km and basin area > 8.2 km2.