On June 18, 2018, under the influence of heavy rainfall, a debris flow disaster broke out in Xigou village of the Three Gorges Reservoir Area in Chongqing, causing some residential houses to be buried along with great economic losses. The on-site investigation found many loose solid material sources in the debris flow gully. Under the conditions of heavy rainfall, debris flows are prone to occur again, which would seriously threaten the lives and property of nearby residents. In this paper, taking the Xigou debris flow as a research case, numerical simulation by rapid mass movements simulation (RAMMS) is used to invert the movement process of the 2018 debris flow event; the dynamic calculation parameters of the Xigou debris flow event are obtained; a quantitative hazard prediction of debris flows with different recurrence intervals (30, 50, and 100 years) is carried out in the study area; and risk assessment is conducted based on the vulnerability characteristics of the disaster-bearing bodies in the study area. The results show that the maximum accumulation thickness of debris flow in the 30-year, 50-year, and 100-year recurrence intervals is 6.54 m, 10.18 m, and 10.00 m, respectively, and the debris flow in the 100-year recurrence interval has the widest influence range and greatest hazard. The low-, medium-, and high-risk areas account for 75%, 23%, and 2%, respectively. The high-risk area mainly includes some buildings near the #1 and #2 gullies. This study provides support for the prevention and control of potential debris flow disasters in Xigou village and a scientific basis for disaster prevention and mitigation in the Three Gorges Reservoir area.
Under the effect of global climate change, the enhanced wave condition leads to lateral erosion at the mangrove vegetation edge, threatening the survival of mangrove habitat and the safety of coastal defense. By means of investigations on sediment physicochemical properties and wave flume experiments, we quantify the lateral erosion rates of mangrove sediments under waves and bridge the edge stability and vegetation with sediment properties. It is found that different mangrove species and stand ages significantly alter the physiochemical properties of sediments, and consequently affect the erosion resistance. Lateral erosion rate is positively correlated with organic matter content and negatively correlated with saturated density, which serve as two main factors that affect sediment resistance to wave forcing. Experimental datasets suggest that the sediment lateral erosion rate of Kandelia obovata reaches several times larger than that of Sonneratia apetala among different stand ages, indicating that the erosion resistance has significant differences between mangrove species. Amongst different Sonneratia apetala sites, the erosion resistance is enhanced with increasing mangrove stand age. This study sheds light on the feedbacks between geo-morphodynamics and intertidal vegetation, which provides a promising experimental approach to evaluate the ecological functions of mangrove forests with respect of resistance to external disturbance. Insights gained from this study is useful in guiding the nature-based solutions for coastal defense through proper spatial-temporal configuration of suitable saplings with higher potential in resilience.
The goal of knowledge representation learning is to embed entities and relations into a low-dimensional, continuous vector space. How to push a model to its limit and obtain better results is of great significance in knowledge graph's applications. We propose a simple and elegant method, Trans-DLR, whose main idea is dynamic learning rate control during training. Our method achieves remarkable improvement, compared with recent GAN-based method. Moreover, we introduce a new negative sampling trick which corrupts not only entities, but also relations, in different probabilities. We also develop an efficient way, which fully utilizes multiprocessing and parallel computing, to speed up evaluation of the model in link prediction tasks. Experiments show that our method is effective.
With the land use data of Dangyang City, Yichang City, Hubei Province in 2000, 2010, and 2020, 13 factors of nature, economy, and society were selected as the driving factors affecting the change of Cropland by using the land-use transition matrix and the kernel density analysis. In this study, the dynamic degree model of cropland use was introduced, combined with the geographic detector method, to explore the spatiotemporal variation characteristics and main driving factors of cropland in various towns in Dangyang City from 2000 to 2020. The results showed that the distribution of cropland generally showed a decreasing trend from southeast to northwest. From 2010 to 2020, the cropland in Dangyang City changed significantly, and the cropland area decreased. Economic and social factors turn out to be the main factors affecting the distribution of cropland. When interacting with other factors, the impact on cropland is weakened, and natural factors have interactive effects on cropland.
Abstract Both natural changes (e.g., tidal forcing from the ocean and global sea level rise) and human‐induced changes (e.g., dredging for navigation, sand excavation, and land reclamation) exert considerable influences on the long‐term evolution of tidal regimes in estuaries. Evaluating the impacts of these factors on tidal‐regime shifts is particularly important for the protection and management of estuarine environments. In this study, an analytical approach is developed to investigate the impacts of estuarine morphological alterations (mean water depth and width convergence length) on tidal hydrodynamics in Lingdingyang Bay, Southeast China. Based on the observed tidal levels from two tidal gauging stations along the channel, tidal wave celerity and tidal damping/amplification rate of different tidal constituents are computed using tidal amplitude and phase of tidal constituents extracted from a standard harmonic analysis. We show that the minimum mean water depth for the whole estuary occurred in 2006, whereas a shift in tidal wave celerity for the M 2 tide component occurred in 2009. As such, the study period (1990–2016) could be separated into pre‐human (1990–2009) and post‐human (2010–2016) phases. Our results show that the damping/amplification rate and celerity of the M 2 tide have increased by 31% (from 7 to 9.2 m −1 ) and 28% (from 7 to 9 m·s −1 ) respectively, as a consequence of the substantial impacts of human interventions. The proposed analytical method is subsequently applied to analyse the historical development of tidal hydrodynamics and regime shifts induced by human interventions, thus linking the evolution of estuarine morphology to the dominant tidal hydrodynamics along the channel. The observed tidal regime shift is primarily caused by channel deepening, which substantially enlarged the estuary and reduced effective bottom friction resulting in faster celerity and stronger wave amplification. Our proposed method for quantifying the impacts of human interventions on tidal regime shifts can inform evidence‐based guidelines for evaluating hydraulic responses to future engineering activities.
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