EARTH SURFACE PROCESSES AND LANDFORMS Earth Surf. Process. Landforms (2013) Copyright © 2013 John Wiley & Sons, Ltd. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/esp.3446 Morphological responses and sediment processes following a typhoon-induced dam failure, Dahan River, Taiwan Desiree Tullos1* and Hsiao-Wen Wang2 1 Department of Biological and Ecological Engineering, 116 Gilmore Hall, Corvallis Oregon, 97331, USA 2 Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Taiwan Received 8 October 2012; Revised 17 May 2013; Accepted 28 May 2013 *Correspondence to: D. Tullos, Department of Biological and Ecological Engineering, 116 Gilmore Hall, Corvallis Oregon, 97331, USA. E-mail: desiree.
[email protected] ABSTRACT: The rates and styles of channel adjustments following an abrupt and voluminous sediment pulse are investigated in the context of site and valley characteristics and time-varying sediment transport regimes. Approximately 10.5 x 106 m3 of stored gravel and sand was exposed when Barlin Dam failed during Typhoon WeiPa in 2007. The dam was located on the Dahan River, Taiwan, a system characterized by steep river gradients, typhoon- and monsoon-driven hydrology, high, episodic sediment supply, and highly variable hydraulic conditions. Topography, bulk sediment samples, aerial photos, and simulated hydraulic conditions are analyzed to investigate temporal and spatial patterns in morphology and likely sediment transport regimes. Results document the rapid response of the reservoir and downstream channel, which occurred primarily through incision and adjustment of channel gra- dient. Hydraulic simulations illustrate how the dominant sediment transport regime likely varies between study periods with sedi- ment yield and caliber and with the frequency and duration of high flows.