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The Taiwan coastal areas are facing predicted sea-level rise effects in the global climate change context. Better understanding of the mechanisms and forcing factors driving the geomorphological evolution of Taiwan's coastline is essential. We highlight the potential of small river estuaries as archives of coastal evolution and provide a paleo-environmental reconstruction of the Gangkou River estuary based on results from a combined methodological approach using geomorphological, sedimentological, and geochronological analyses. A consistent chronology was established by combining Optically Stimulated Luminescence (OSL) dating, as well as radiocarbon dating techniques. A distinct beach-rock layer allowed firm correlation of six investigated coastal profiles. Eustatic sea level change was identified as the primary coastal and estuarine landscape development forcing factor in the study area. Tectonic forcing could also be detected from the investigated sites, but has to be regarded as a subordinate secondary forcing factor. The Gangkou River estuary developed in the early Holocene at about 8 ka and was fully developed by the time the Holocene sea-level maximum was reached. With the sea-level dropping until modern times, estuarine zone relocation and a transition to terrestrial processes was initiated, leading to development of the current coastal dune system since about 2.5 ka. Major dune building phases correlate with the climate change associated with the Little Ice Age (LIA) event and stabilised towards recent times, which is in accordance with regional and over-regional coastal Aeolian records in Taiwan.

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We identified four climatic stages between 6.2 and 1.3 cal kyr before present (BP) based on pollen and charcoal concentrations by high-resolution Accelerated mass spectrometer (AMS) 14 C-dated sediment profile from Taiwan's Toushe Basin. From 6.2 to 4.6 cal kyr BP, the region was warm-wet with infrequent wildfires and dominant subtropical evergreen broad-leaved forests. The climate was cooler-drier from 4.6 to 3.0 cal kyr BP, with a decline in forest and increased fire frequency. From 3.0 to 2.1 cal kyr BP, climate further cooled and dried, with the development of alpine meadows and higher fire frequency. The region became warmer and wetter from 2.1 to 1.3 cal kyr BP, accompanied by forest recovery. Climatic changes were linked to changes in East Asia Summer Monsoon intensity, which is mainly controlled by solar radiation. Wildfires were likely controlled by precipitation variability that is influenced by East Asia Summer Monsoon and El Niño-Southern Oscillation. Toushe Basin experienced drought conditions and frequent wildfires during the El Niño years. Plain Language Summary The purpose of our study is to reveal the relationship between paleoclimate, vegetation, and wildfire. The study area is located in the Toushe Basin, central Taiwan. Through palynological and charcoal analysis, the vegetation, climate, and wildfire history of the past 6,000 to 1,000 years in the study area were reconstructed. The study found that after 4,600 years, the East Asian summer monsoon continued to weaken until approximately 2,000 years ago, during which time the climate was dry and cool, and wildfires were frequent. In addition, it is found that the climate in this region is mainly controlled by the changes in solar radiation. The cycle of climate change coincides with that of solar activity. In El Niño years, the Toushe Basin was dry and frequent wildfires occurred.

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This paper explores the combination of unmanned aerial vehicle (UAV) photogrammetry and an e-GNSS survey to investigate the short-term geomorphic change and dynamic evolution of a beach system in 2015. The RMS values of the ground control points and checkpoints validate that the accuracy of UAV-SfM photogrammetry is suitable for the rapid and frequent acquisition of 3D survey data from a beach environment. We produced four digital surface models (DSMs) to determine the short-term beach topographic response to well-known western Pacific typhoons, the NE monsoon and anthropogenic construction using multitemporal surface analysis. We investigated the magnitude of the erosion caused by intense typhoons; however, the beach-dune system generally recovers through sediment transport processes in winter. Beach monitoring also reveals that the overall sand volume of this beach was reducing in short-term period. Given that the sand budget of Shanshui beach would have been continuing to reduce, this may be a negative warning to this precious tourism resource. The dynamic evolution of this beach may result in the formation of a tombolo. This study demonstrates the feasibility and survey efficiency of UAV-SfM photogrammetry for coastal monitoring, and the technique will contribute to identifying the risk to beach systems and will benefit sustainable coastal management.

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