Quasi-2D transport model of suspended sediment in a wave flume

A quasi-2D model of hydrodynamics and sediment transport has been developed in this study. An\ud eddy viscosity model with a function of artificial viscosity has been applied to the Boussinesq-type\ud equations to produce wave decay as well as sediment transport due to breaking. Numerical results are\ud then compared with laboratory experimental data in order to verify the applicability of the numerical\ud model. The results demonstrate that the proposed eddy viscosity model can be used to simulate wave\ud propagation in the surf zone as well as suspended concentration distribution. Erosion before the breaking\ud point can be predicted fairly well. However, the bar crest and erosion in the surf zone can not be predicted\ud accurately

Coupling of Boussinesq and sediment transport model in a wave flume

Boussinesq type equation has been coupled with sediment transport model to simulate sediment\ud transport in a wave flume. A new eddy viscosity model has been applied to calculate wave decay as well\ud as suspended sediment concentration. A bed load transport formula based on an energetic transport of\ud Bagnold-type model combined with suspended load model was validated under the condition of a spilling\ud wave. The applicability of both ??B and cf has been investigated. The result indicated that two sets of\ud parameters cf = 0.017 with ??B = 0.21 and cf = 0.003 with ??B = 1.03 calculated a similar bed level change.\ud Comparison of calculated and measured bed level change is fairly good in offshore and near breaking\ud point. However, the model cannot predict accretion in swash zone

Effect of Urbanization Distribution on Flood Simulation

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Downscaling Global Weather Forecast Outputs Using ANN for Flood Prediction

Downscaling global weather prediction model outputs to individual locations or local scales is a common practice for operational weather forecast in order to correct the model outputs at subgrid scales. This paper presents an empirical-statistical downscaling method for precipitation prediction which uses a feed-forward multilayer perceptron (MLP) neural network. The MLP architecture was optimized by considering physical bases that determine the circulation of atmospheric variables. Downscaled precipitation was then used as inputs to the super tank model (runoff model) for flood prediction. The case study was conducted for the Thu Bon River Basin, located in Central Vietnam. Study results showed that the precipitation predicted by MLP outperformed that directly obtained from model outputs or downscaled using multiple linear regression. Consequently, flood forecast based on the downscaled precipitation was very encouraging. It has demonstrated as a robust technology, simple to implement, reliable, and universal application for flood prediction through the combination of downscaling model and super tank model

POST-FLOOD NUTRIENT DISTRIBUTION PHENOMENA IN COASTAL WATERS OFF RIVER MOUTH

High discharge caused by river flood can affect the water quality of downstream river, and coastal area where this river releasing its water. To investigate the effect of river flood on nutrient distribution, two field measurements were conducted, i.e November 2, 2001, July 20, 2002, representing usual condition and after flood condition respectively. Research site is coastal area of the Abukuma River mouth, Japan with eight sampling stations. The results show that the river flood affected water quality by increasing the concentration of suspended solid and nutrient. River mouth waters contain remarkably high concentration of nitrogen (4.4 mg/L) after river flood. Nitrogen and phosphorus were distributed as the function of distance to the river mouth in usual condition. However, condition after river flood show that nutrient had been brought far to the offshore, indicated by the higher concentration in stations located far from the river mouth. For nitrogen path, nitrification process was likely to be occurred in surface layer of coastal area, whereas detritus decomposition occurred in bottom layer. Settling process in coastal waters appeared dominant in phosphorus path after the flood. Keywords: River flood, nutrient distribution, open coastal water

Temporal and spatial differences of methane flux at arctic tundra in Alaska

High latitude ecosystems were thought to enhance CH_4 emission in relation to the current arctic warming. However, we have little information about this potential feedback mechanisms on climate change, thus, model parameterization is insufficient and the observational data are required. We observed CH_4 flux at several types of tundra in Alaska over the growing seasons since 1995. From these observed data, we examined current CH_4 emission and its controlling factors on Alaskan tundra. Then we discussed about spatial and temporal differences in CH_4 flux. Daily trend of half hourly CH_4 flux had little relation with soil temperature, but the seasonal trend of daily flux changed with soil or water temperature. Cumulative CH_4 fluxes during the growing seasons were 8.1gCH_4m^(-2) on wet sedge tundra at Happy Valley in 1995, 3.3gCH_4m^(-2) on non-acidic moist tundra in 1996, and 3.58-8.24gCH_4m^(-2) on wet sedge tundra at Barrow between 1999-2003. Non-acidic tundra had low CH_4 emission with low CO_2 accumulation. There was large spatial difference in CH_4 flux caused by tundra type, and the large temporal difference at the wet sedge tundra reflected yearly weather variability

Minimally Invasive Surgery for Intraocular Lens Removal and Intrascleral Intraocular Lens Fixation with Trabeculectomy in a Patient with Dislocated Intraocular Lens and Elevated Intraocular Pressure

A 88-year-old female who was being treated for end-stage pseudoexfoliation syndrome was referred to our hospital for treatment of dislocated intraocular lens (IOL) and the elevated intraocular pressure (IOP) and in the right eye (RE). At the first visit to our hospital, best-corrected visual acuity (BCVA) was 0.2 in the RE and 0.02 in the left eye (LE). IOP was 47 mm Hg in the RE and 21 mm Hg in the LE. Slit-lamp examination showed no abnormalities in anterior segments and dislocated IOL in the RE. Fundus photograph showed optic disc pallor in both eyes. We performed the combined therapy of flanged intrascleral IOL fixation with the double-needle technique and trabeculectomy. Throughout the follow-up period, BCVA slightly improved from 0.2 to 0.4 in the RE. The angle of tilt of the IOL was 6.6, 7.9, and 8.7° as measured by swept-source optical coherence tomography at 1, 4, and 6 months after the surgery, respectively. The IOP remained less than 10 mm Hg without having to administer any other glaucoma medications. Furthermore, any complications associated with the surgery were not confirmed

Microbial mat compositions and localization patterns explain the virulence of black band disease in corals

Black band disease (BBD) in corals is characterized by a distinctive, band-like microbial mat, which spreads across the tissues and often kills infected colonies. The microbial mat is dominated by cyanobacteria but also commonly contains sulfide-oxidizing bacteria (SOB), sulfate-reducing bacteria (SRB), and other microbes. The migration rate in BBD varies across different environmental conditions, including temperature, light, and pH. However, whether variations in the migration rates reflect differences in the microbial consortium within the BBD mat remains unknown. Here, we show that the micro-scale surface structure, bacterial composition, and spatial distribution differed across BBD lesions with different migration rates. The migration rate was positively correlated with the relative abundance of potential SOBs belonging to Arcobacteraceae localized in the middle layer within the mat and negatively correlated with the relative abundance of other potential SOBs belonging to Rhodobacteraceae. Our study highlights the microbial composition in BBD as an important determinant of virulence