Meteorological disasters (MDs), including drought, flood, hail, low temperature and frost (LTF), are causing severe damage to human life and economic development in China. Mapping the distribution of ...MDs and induced losses at fine spatial resolution across the whole country is helpful for disaster control. Based on the officially published records and yearbooks, the spatiotemporal variations in MD frequency at prefecture-level city scale and disaster-induced losses at provincial scale during 2011–2019 were analyzed. The result showed that there were average 1416.9 MD events every year at prefecture-level city scale. Flood and hail disasters dominated from April to September, while LTF disasters dominated from December to February. Drought disasters were mainly distributed at the second terrain step and North China Plain; frequency of flood disasters in the south part of China was higher than that in the north part of China, especially in the upper and middle reaches of Yangtze River basin; while the north part of China experienced higher frequency of hail and LTF than the south part. Cities on the second terrain step of China experienced the largest MD frequency because of the combination of disaster-causing factors and hazard-bearing body. Disaster loss analysis results showed that drought disasters had the severest effects on cropland because of the highest average covered and failed area of cropland among four MDs. Hunan, Hubei and Sichuan provinces experienced higher values of covered population and direct economic losses, while coastal provinces experienced less exposure to MDs. The results of this study can help optimal allocation of disaster mitigation and adaptive measures at both country and regional scales.
Human activity recognition (HAR) has become a popular topic in research because of its wide application. With the development of deep learning, new ideas have appeared to address HAR problems. Here, ...a deep network architecture using residual bidirectional long short-term memory (LSTM) is proposed. The advantages of the new network include that a bidirectional connection can concatenate the positive time direction (forward state) and the negative time direction (backward state). Second, residual connections between stacked cells act as shortcut for gradients, effectively avoiding the gradient vanishing problem. Generally, the proposed network shows improvements on both the temporal (using bidirectional cells) and the spatial (residual connections stacked) dimensions, aiming to enhance the recognition rate. When testing with the Opportunity dataset and the public domain UCI dataset, the accuracy is significantly improved compared with previous results.
•Magnetite nanoparticle supported on sepiolite (Fe3O4-Sep) was fabricated.•Fe3O4-Sep showed high adsorption ability toward BPA.•Adsorbed BPA can be degraded in-situ via Fenton-like process.•Columnar ...Fe3O4-Sep remained stable in the fixed-bed reactor under continuous-flow.•Influence of real water matrix on the combined processes was negligible.
In this work, a magnetic sepiolite composite was prepared by chemical co-precipitation method and firstly applied as both adsorbent and catalyst for the removal of bisphenol A (BPA) through a heterogeneous Fenton process. The composite was characterized by XPS, XRD, SEM and TEM techniques. The results of the kinetics study indicate that BPA (50 mg·L−1) can be adsorbed onto the composite via electrons transfer as well as π-π interaction, and then be completely degraded at pH 6.0 within 30 min after the addition of H2O2 (1000 mg·L−1). The analysis of FTIR confirms that the degradation occurred through a combined process of adsorption and oxidation. BPA was pre-concentrated and fixed onto the composite surface and then degraded in-situ by hydroxyl radicals, which were generated through the interaction between H2O2 and surface active sites. To investigate the stability and regeneration properties of the catalyst, the powder composite was extruded into a small cylindrical sample and loaded in a fixed-bed reactor, which was operated under continuous-flow condition. The BPA removal efficiency after 4 h remained at 87%, while the leaching of Fe ions gradually increased. Further, degradation tests in different real waters including tap water and municipal wastewater spiked with BPA (50 μg·L−1) reveal that the influence of real matrix on the oxidation ability was very little. The findings of this study confirm the composite as a promising material for the catalytic removal of organics via the coupled adsorption-oxidation process.
•Spatial distributions of flow hydraulics are quantified in an ephemeral gully system.•Flow zones in ephemeral gully system are distinguished by their flow regimes.•Rainfall intensity, slope, upslope ...and lateral inflows impact the flow hydraulics.•Shear stress was found to be best correlated with sediment loads of the EG system.
Overland flow in an ephemeral gully (EG) system includes the EG channel, rill and interrill sheet flows, which comprise an interconnected drainage network. There are abundant researches on the hydraulics of rill flow and interrill sheet flow, as well as their relationships with soil detachment rates and sediment loads. Few studies have quantified the flow hydraulics of EG system which is highly related to the EG erosion and the development of better EG management strategies. Thus, two erosive rainfall intensities (50 and 100 mm h−1) and two slope gradients (15° and 20°) under different upslope and lateral inflow boundary conditions were employed to study the flow hydraulics of an EG system using simulated rainfall and inflow experiments. The results showed that flow velocity, shear stress, stream power and cross-sectional energy in the EG channel generally increased from the top to bottom of the slope with different trends and fluctuations under various inflow conditions. The flow hydraulic parameters of EG channel, rill, and interrill sheet flows all increased as rainfall intensity and slope increased. Flow regimes in the EG system were divided based upon the Reynolds number and Froude number. EG channel flow was classified as transitional to turbulent flow, rill flow was transitional, while sheet flows on interrill areas was laminar. From sheet flow to rill flow and EG channel flow, the flow regime gradually shifted from laminar and subcritical flow to turbulent and supercritical flow. The flow force, power and energy correspondingly increase as flow regime changed toward turbulent and supercritical. Good relationships between sediment load and flow hydraulic parameters were observed and flow shear stress was found to be best correlated with soil erosion of the EG system (R2 = 0.92). This study quantitively mapped the flow hydraulics in the EG system and correlated these with erosion features, contributing to the development of process-based EG prediction models and better EG management strategies.
Channels (rill, ephemeral gully, gully and river channel) exhibit a continuum of sizes and flow magnitudes. Rill erosion, as the initial stage of channel erosion, accounts for >80% of total eroded ...sediments on sloping farming lands in many parts of the world. Previous researches often regard rill erosion as an entirety or focus on individual rill erosion process separately. Few attentions have been paid to the contributions of individual processes including rill headcut advance, bed incision, sidewall expansion and their interactions to the over-all rill erosion. Thus, simulated upslope inflow experiments were designed to investigate the impacts of individual processes involved and their interactions in rill erosion under four inflow rates (1.0, 2.0, 3.0 and 4.0 L min−1) and two slope gradients (15° and 20°). Photogrammetry and manual sampling were used to measure hillslope morphology variation and sediment delivery, repectively. The results show that headcut advance, bed incision and sidewall expansion interact with each other and exhibit both independent and dependent features across spatial and temporal scales. Headcut advance interacts with bed incision and sidewall expansion before rill head advancing to a critical slope length. Initial rill depth and width are determined by initial headcut morphology. Bed incision and sidewall expansion dominate rill erosion before and after the non-erodible layer is exposed to concentrated flow, respectively. Headcut advance contributed the largest amount of rill erosion (44%–68%), followed by bed incision (27%–44%) and sidewall expansion (3.8%–12%). Headcut advance contributed more (63%–83%) to total rill width increment while bed incision contributed larger percentage (51%–65%) to total rill depth increment. Prediction equations for length, width and depth of a single rill on a loessial hillslope and empirical equations of rill erosion for the individual erosion processes were fitted and validated. Quantification and understanding of the contributions of individual rill erosion processes provides the necessary scientific basis for the development of process-based rill erosion models, and then, for preventions of soil losses and land degradation.
•Contributions of individual rill erosion processes to rill development were quantified.•Prediction equations for length, width and depth of a single rill were fitted.•Empirical equations of rill erosion for the individual erosion processes were fitted.
Satellite-based precipitation estimates (SPEs) show great promise for promoting landslide warning and mitigating landslide disaster risk with quasi-global coverage, near real-time monitoring, ...increasing spatial-temporal resolution, and accuracy. In this study, we evaluated the performances of four SPE products in detecting the initiation of rainfall-induced landslides globally using Hanssen-Kuiper (HK) skill score based on rainfall frequentist thresholds. The results show that SPEs can distinguish rainfall events responsible for landslides from those not related to landslides, suggesting that SPEs can capture rainfall conditions corresponding to landslide occurrence well and are of great use for landslide detecting. Further investigation indicates that performances at the global scale vary with products. CMORPH-3h V1 (HK = 0.43) and TMPA-3B42RT V7 (HK = 0.42) are superior to two other rainfall products with high HK values. Rainfall threshold establishment and evaluation for specific landslide types can improve SPEs’ performances in landslide modeling with higher HK values compared to results based on all landslide records. Performances also vary spatially with HK values ranging from 0.1 to 0.9 at a spatial grid of 5° × 5°. Linear relationship analysis reveals the variation in mean annual precipitation can partially explain the heterogeneous spatial distribution of rainfall threshold parameters. These findings serve to promote the application of satellite-based rainfall data in landslide warnings.
Identification of drought is essential for many environmental and agricultural applications. To further understand drought, this study presented spatial and temporal variations of drought based on ...satellite derived Vegetation Condition Index (VCI) on annual (Jan⁻Dec), seasonal monsoon (Jun⁻Nov) and pre-monsoon (Mar⁻May) scales from 1982⁻2015 in Nepal. The Vegetation Condition Index (VCI) obtained from NOAA, AVHRR (National Oceanic and Atmospheric Administration, Advanced Very High Resolution Radiometer) and climate data from meteorological stations were used. VCI was used to grade the drought, and the Mann⁻Kendall test and linear trend analysis were conducted to examine drought trends and the Pearson correlation between VCI and climatic factors (i.e., temperature and precipitation) was also acquired. The results identified that severe drought was identified in 1982, 1984, 1985 and 2000 on all time scales. However, VCI has increased at the rate of 1.14 yr
(
= 0.04), 1.31 yr
(
= 0.03) and 0.77 yr
(
= 0.77) on the annual, seasonal monsoon and pre-monsoon scales, respectively. These increased VCIs indicated decreases in drought. However, spatially, increased trends of drought were also found in some regions in Nepal. For instance, northern areas mainly in the Trans-Himalayan regions identified severe drought. The foothills and the lowlands of Terai (southern Nepal) experienced normal VCI, i.e., no drought. Similarly, the Anomaly Vegetation Condition Index (AVCI) was mostly negative before 2000 which indicated deficient soil moisture. The exceedance probability analysis results on the annual time scale showed that there was a 20% chance of occurring severe drought (VCI ≤ 35%) and a 35% chance of occurring normal drought (35% ≤ VCI ≤ 50%) in Nepal. Drought was also linked with climates in which temperature on the annual and seasonal monsoon scales was significant and positively correlated with VCI. Drought occurrence and trends in Nepal need to be further studied for comprehensive information and understanding.
Ephemeral gullies (EGs) are major contributors to sediment loss and land degradation on cultivated lands. However, the topography and rainfall impacts on EG development processes are still unclear, ...especially on steep loessial hillslopes such as the Loess Plateau. A series of laboratory rainfall simulation experiments were conducted to investigate the impacts of topographic characteristics (3 typical slope gradients (S): 26.8%, 36.4%, and 46.6%; and 5 upslope drainage areas (A): 16, 32, 64, 96, and 128 m2) and rainfall intensities (3 representative erosive rainfall intensities 50, 75, and 100 mm hr−1) on EG erosion on a steep loessial hillslope. A large slope adjustable soil pan (8 m‐long, 2 m‐wide, and 0.6 m‐deep) and a side‐sprinkler rainfall simulation system were used in this study. The results showed that soil loss increased when rainfall intensity, slope, and upslope drainage area increased. Upslope topography and inflow had great impacts on downslope EG erosion, and the contribution percentages ranged from 52.2% to 74.1%, from 48.3% to 71.4%, and from 29.5% to 66.7% for the 50, 75, and 100 mm hr−1 rainfall treatments, respectively. Runoff velocities with upslope inflow were 22.7% to 79.4% larger than those without inflow, and the upslope inflow was more effective than rainfall intensity in increasing runoff velocities in EG channels, thus caused more soil erosion. Soil loss equation based on rainfall intensity and AS2 (product of the upslope drainage area and the square of the local slope gradient) was established and validated. The determination coefficient (R2) and Nash–Sutcliffe simulation efficiency (ENS) were 0.80 and 0.87, which showed satisfactory accuracy. This equation can be used to predict the EG erosion in various topographic and rainfall conditions on steep loessial hillslopes.
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