Hydrogeomorphological differentiation between floodplains and terraces. Issue 1 (4th October 2017)

• Record Type: Journal Article
• Authors: Yan, Qina; Iwasaki, Toshiki; Stumpf, Andrew; Belmont, Patrick; Parker, Gary; Kumar, Praveen
• Is Part Of: Earth surface processes and landforms. Volume 43:Issue 1(2018)
• Page Start: 218
• Page End: 228
• Publication Date: 2017-10-04
• Subjects: river valley -- hydrogeomorphology -- flood simulation -- floodplain and terrace; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4234
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Floodplains and terraces in river valleys play important roles in the transport dynamics of water and sediment. While flat areas in river valleys can be identified from LiDAR data, directly characterizing them as either floodplain or terraces is not yet possible. To address this challenge, we hypothesize that, since geomorphic features are strongly coupled to hydrological and hydraulic dynamics and their associated variability, there exists a return frequency, or possibly a narrow band of return frequencies, of flow that is associated with floodplain formation; and this association can provide a distinctive signature for distinguishing them from terraces. Based on this hypothesis we develop a novel approach for distinguishing between floodplains and terraces that involves transforming the transverse cross‐sectional geometry of a river valley into a curve, named a river valley hypsometric (RVH) curve, and linking hydraulic inundation frequency with the features of this curve. Our approach establishes that the demarcation between floodplains and terraces can be established from the structure of steps and risers in the RVH curves which can be obtained from the DEM data. Further, it shows that these transitions may themselves be shaped by floods with 10‐ to 100‐year recurrence. We additionally show that, when floodplain width and height (above channel bottom) are normalized by bankfull width and depth, the ratio lies in a narrow range independent of the scale of the river valley. Copyright © 2017 John Wiley & Sons, Ltd. Abstract : Floodplains and terraces in river valleys play important roles in the transport dynamics of water and sediment. However, directly characterizing flat areas, identified from data, as either floodplain or terrace is not yet possible. We develop a novel approach for distinguishing between them that involves creating a river valley hypsometric (RVH) curve, and linking flooding frequency with this curve. The geometry of the RVH curve demarcates clear boundaries between floodplains and terraces. We find that the transitions between floodplains and terraces may be shaped by floods with 10‐ to 100‐year recurrence.