The influence of landscape configuration upon patterns of sediment storage in a highly connected river system

Orthoimages are used to analyze the influence of valley width, channel slope, and the area of landslides that deliver sediment to valley floors upon the downstream pattern of sediment storage in the Liwu basin, eastern Taiwan. Confined valley settings dominate this steep, deeply dissected, uplifting mountainous basin. Although they occupy 82% of the whole channel network, sediment storage is limited in these reaches. Partly confined valley settings are restricted to relatively short reaches of two tributary systems. Over 95% of sediment storage in the Liwu River is found within the short alluvial section of laterally unconfined valley close to the river mouth. Lateral bars are the primary features associated with sediment storage in confined reaches (54% in total volume), while floodplains dominate the partly confined and laterally unconfined reaches (95% in total volume). Downstream patterns of sediment storage are controlled primarily by valley confinement (i.e., valley width) and landscape configuration. Channel slope and locations of contemporary landslides are not key determinants of sediment storage patterns. Sediment accumulation at confluence zones is not determined by the catchment area of tributaries or by landslide area; rather, it is determined by valley confinement of the trunk stream at the confluence and the associated downstream sequence of river types. Sediment conveyance is very effective within this highly connected river system.

► Sediment storage is controlled mainly by valley width and landscape configuration.
► Over 80% of the channel network is composed of confined valley settings.
► Over 95% of sediment storage volume is found within the laterally unconfined valley.
► Channel slope and area of landslide are not key determinants upon sediment storage.