Geomorphological Change Detection Using an Integrated Method: A Case Study on the Taan River Watershed, Taiwan

Abstract

The Chi-Chi earthquake of 1999 in Central Taiwan caused significant vertical uplift and ignited a dynamic fluvial erosion system in the Taan River. In order to understand the geomorphologic changes in the Taan River after the Chi-Chi earthquake, this study uses multi-temporal aerial photos to produce orthoimages and surface models to derive regional three dimensional movements from 2001 -2009. The Particle Image Velocimetry (PIV) technique is applied to identify the horizontal movements from both orthoimages and digital surface models (DSMs). While PIV can provide estimates for the channel change direction and magnitude; vertical analysis such as river incision rate derivation could be performed using the height difference between multi-temporal surface models. The results from these two approaches are then integrated for river geomorphological interpretation. It is observed that the proposed scheme is capable of identifying three river evolution stages from the extracted movements in the Taan case. These stages are: years 2001 to 2003, 2004 to 2006, and 2007 to 2009, respectively. The total incision between 2001 and 2009 is about 10 m. This study demonstrates that both PIV and DSM subtraction are effective in river geomorphological change identification. The integration of these two approaches could provide more information when observing the evolution of river morphology.

The Benefit of the Geospatial-Related Waveforms Analysis to Extract Weak Laser Pulses

“…The DSM represents the 3D surface (e.g., building height), whereas the DTM is a topographic model of the bare earth (i.e., ground model). The DSM is commonly used in city modeling and land cover classification [2], whereas the DTM is often required for geological analysis [3,4]. Both models provide useful geospatial data to represent the 3D shapes of the Earth.…”