Fengling Yu

An evolutionary model for the Holocene formation of the Pearl River delta, China

This paper reconstructs the evolutionary history of the Pearl River delta over the last 9000 years and investigates land—sea interaction in a large deltaic complex which formed under the influence of Asian monsoon climate. Specifically, this research examines the delta evolution in the context of three driving mechanisms: (1) rising sea level that influences the available accommodation space, (2) fluvial discharge as influenced by monsoon climate and (3) human activities that alter sedimentation within the deltaic system. Results reveal that the formation of deltaic sequences was initiated as a consequence of rapid sea-level rise between 9000 and 7000 cal. yr BP. The rate of sea-level rise slowed down markedly around 7000 cal. yr BP and sedimentation switched from transgressive to regressive. Initially, both the progradation of the delta plains near the apex and aggradation of delta front sedimentation in the central and lower parts of the receiving basin were fast owing to strong monsoonal-driven runoff. The progradation rate gradually slowed down between 6800 and 2000 cal. yr BP as monsoonal-driven runoff weakened. Rapid shoreline advances during the last 2000 years were the result of significantly increased human activities, a practice that trapped sediments in the encircled tidal flats along the front of delta plains. The evolutionary history of the Pearl River delta demonstrates the interplay between the three driving mechanisms.

Mid-holocene variability of the East Asian monsoon based on bulk organic δ13C and C/N records from the Pearl River estuary, southern China

Understanding the mid-Holocene dynamics of the East Asian monsoon (EAM) is integral to improving models of the Holocene development of the global climate system. Here we reconstruct the mid-Holocene EAM history from the Pearl River estuary, southern China, using bulk organic carbon isotopes (δ13C), total carbon to total nitrogen (C/N) ratios and total organic carbon (TOC) concentration. Sedimentary δ13C, C/N and TOC are potentially good indicators of changes in monsoonal precipitation strength. Sediments buried during a period of high precipitation exhibit a high proportion of terrigenous material, and have low δ13C and high C/N, and vice versa during a period of low precipitation. Results suggest a general decreasing trend in monsoonal precipitation from 6650 to 2150 cal. yr BP because of the weakening Northern Hemisphere insolation most likely related to the current precession circle. Superimposed on this trend are apparent dry–wet oscillations at centennial to millennial timescales most likely in response to solar activity. Mismatches between our δ13C record and results from the Dongge Cave in southern China at millennial timescales may indicate that the δ13C from the Pearl River estuary reveals changes in precipitation over a broader area than the δ18O from Dongge Cave.

Integrating different records to assess coastal hazards at multi-century timescales

ABSTRACT Switzer, A.D., Yu, F., Gouramanis, C, Soria, J, Pham, T.D. 2014. An integrated approach to assessing coastal hazards at multi-century timescales. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 723–728, ISSN 0749-0208. In many places on earth, the written record of coastal flooding events from tropical cyclones (typhoons, hurricanes) and tsunamis is too short or inconsistent to accurately assess the hazard posed by both kinds of event on scales beyond those of the average human lifespan. In this paper we summarize an integrated research paradigm that incorporates instrumental, historical, archaeological and geological records to extend the record of coastal flooding events to generate a multi-century analysis of recurrence interval for coastal flooding, thus, improving long-term risk assessment. The two primary factors in assessing risk from coastal hazards are frequency and magnitude. These can be addressed through field and modeling studies of washover deposits where they are found. We also summarize recent advances in the identification of overwash events from the geological record and report on the progress to distinguish storm and tsunami deposits. The recent advances have increased the utility of tsunami and storm deposits to improve coastal risk assessment.

Developing a Historical Typhoon Database for the Southeastern Chinese Coastal Provinces, 1951-2010

Many countries have developed their own typhoon database for the use in understanding historical typhoon. However, when each database is compared, inconsistencies are evident in terms of the depth of information provided. This paper outlines the development of a combined database and provides comprehensive details of typhoons impacting the southeastern Chinese coastal provinces of Fujian, Guangdong, Hainan, Hong Kong, Macau, Taiwan and Zhejiang. The database is titled “A historical typhoon database for the southeastern Chinese coastal provinces, 1951-2010” and contains entries for 581 reported typhoon events that have occurred between 1951 and 2010, with standard typhoon information presented where obtainable. Importantly, additional information on the number of casualties is included for 265 typhoon events that have records of the death toll, and 131 events that have records of the economic loss caused by each event. Using this new database, we highlight the worst typhoon events that have impacted the southeastern Chinese coastal provinces in terms of fatalities from 1951 to 2010. A decreasing trend in both the number of fatalities and economic loss are recorded for the entire data period for the former and since 1993 for the latter.

Using Geology as a Tool for Assessing Coastal Risk in Asia

In many places in Asia, the written record of typhoons (tropical cyclones) and tsunamis is too short or inconsistent to accurately assess the risk of coastal disasters from both kinds of event. Here we propose that sedimentary deposits left by overwash events attributed to past typhoons or tsunamis can be used to extend the record of overwash, and generate an analysis of recurrence interval, thus, improving long-term risk assessment. The two primary factors in assessing coastal hazard risk are frequency and magnitude. These can be addressed through field and modeling studies of deposits where they are found. Recent advances in identification of overwash deposits along with progress on attempts to distinguish between storm and tsunami sedimentation, have increased the utility of using overwash deposits to improve coastal risk assessment.