Mild Slope Research Articles

Strongly dispersive internal solitary waves transformation over slope-shelf topography

The evolution of strongly dispersive internal solitary waves (ISWs) over slope-shelf topography is studied in a two-layer system of finite depth. We consider the high-order vmeKdV model extending the Korteweg-de Vries (KdV) equation with coupling terms of [Formula: see text] order to treat the strong dispersion in the problem which has variable coefficients to adapt the varying bottom topography. The strongly dispersive initial ISW is characterized by the meKdV equation according to the comparison with experiments and can be propagated by the vmeKdV equation according to the comparison between vmeKdV and vKdV theories. The vmeKdV equation is numerically implemented adopting the finite difference scheme. Three dimensionless ISW amplitudes [Formula: see text], 1.136, 1.41 and two slope inclinations [Formula: see text], 1/10 are considered. The deformation of the ISW is observed when a wave propagates past over the slope. The balancing of shoaling effect and energy dispersion determine the amplitude variation. In the cases of mild or steeper slopes, the terminal wave has a stable profile and amplitude, commonly consistent to the meKdV profile with smaller amplitude. In a particular case of mild slope with very small initial amplitude, the terminal wave amplitude grows larger than the original value.

Numerical Analysis of Wave Run-up Characteristics on Dual Non-submerged Vertical Cylinders

In this paper, a numerical model is set up to solve the mild slope equation proposed by Berkhoff using the finite element method. The computational result of wave run-up on a single non-submerged vertical cylinder matches well with the analytical solution, verifying the validity of the numerical model. The effect of the spacing between two cylinders on wave run-up is discussed. The results show that the position of maximum and minimum wave run-up on the upstream cylinder is almost the same with that of a single cylinder, but when the spacing is odd or even times of one quarter of incident wavelength, the secondary maximum or minimum wave run-up appears at the both sides of the cylinder. The curves of wave run-up on the downstream cylinder is similar but smaller than that of a single cylinder.

Wave-current interactions during extreme weather conditions in southwest of Bohai Bay, China

Wave-current interactions widely occur in shallow waters. However, the dominant factors for the modulation differ over different coastal regions and the relevant generation mechanisms have not been fully addressed. In this study, a Delft3D wave-current coupled model is applied to the southwestern Bohai Bay, China, which is a shallow-water coast with a mild slope, to estimate the local wave-current interactions during extreme weathers. The results indicate that the wave set-up is strongly influenced by local bottom slope, water depth and radiation stress gradient. The mean current velocity is decreased by wave by up to 15% due to enhanced bottom roughness, and the impact of momentum transfer from wave to current is non-negligible. Both tidally-varying depth and current are able to modulate significant wave height (SWH), and their modulating abilities are increased and decreased onshore respectively. Furthermore, the sensitivity studies suggest that the depth-induced SWH modulation is primarily due to the shoaling effect which is related to bottom slope. The wind speed plays an important role on the depth- and current-induced SWH modulation, as it could affect the state of wind-wave and wind input energy. Whereas, wind direction change from onshore to offshore only results in remarkable changes of current-induced modulation.

Experiments, Correlation, and Modeling of Curcumin Solubility in Subcritical Water (Water/Ethanol)

The solubility of curcumin in the pure water subcritical and water–ethanol solution (water + (5–10) % (v/v) ethanol) subcritical is investigated for the first time. The design approach taken from this study is the response surface methodology due to the Box Behnken. The experiments were performed in the temperature range of (90–150) °C, (0–10) volumetric percent of ethanol and the flow rate of (0.2–0.8) ml/min. As the pressure effect is ignored in the subcritical conditions, the pressure is constant in 2 MP in the experiments. All analyses were carried out employing the high-performance liquid chromatography apparatus. The curcumin solubility data were correlated with the dielectric constant of solvent mixture. Curcumin solubility modeling in subcritical conditions was done due to cubic-plus-association equation of state. The present study indicated that the rise in temperature and ethanol percentage cause an increase in curcumin solubility. Other important finding was by increasing the flow rate, curcumin solubility rate increased with a very mild slope. The optimum conditions for the curcumin solubility were in the water flow rate of 0.8 ml/min, 10% (v/v) of ethanol, and the temperature of 150 °C.

Screening of Organic Substrates for Solid-State Fermentation, Viability and Bioefficacy of Trichoderma harzianum AS12-2, a Biocontrol Strain Against Rice Sheath Blight Disease

The present study was undertaken to find the most suitable organic substrates for the biomass production, viability and efficacy of the biocontrol strain Trichoderma harzianum AS12-2 in the solid-state fermentation system. In total, 13 inexpensive, locally available substrates (agricultural wastes or by-products) were inoculated with the antagonist, and following one month of incubation at room temperature, all colonized substrates were air dried and ground to powder. The shelf life and viability of the Trichoderma strain were assessed as colony-forming units per gram (CFUs g−1) of each substrate on a monthly basis for up to one year at room temperature (25 ± 2 °C) and in the refrigerator (4 °C). In order to find out the effect of the substrate on the bioefficacy of T. harzianum AS12-2, the biocontrol potential of the formulations was evaluated against rice sheath blight disease caused by Rhizoctonia solani. The results showed that the fungus colonized more or less all substrates after one month, although the degree of colonization and conidiation was different among the substrates, being especially high in broom sorghum grain, rice husk, rice straw, rice bran and sugar beet pulp. Analysis of variance (ANOVA) of the population in the substrates in “Month 0” showed that the effect of treatment was significant, and the means were significantly different. The maximum population was recorded for broom sorghum grain and rice straw (6.4 × 1010 and 5.3 × 1010 CFUs g−1, respectively). The population declined in all substrates after one year of incubation at room temperature. This decline was relatively smaller in broom sorghum grain, rice straw and rice husk. On the other hand, the population in the same substrate incubated in the refrigerator was decreased in a mild slope, and the final population was high. In addition, the results of greenhouse assay showed that all bioformulations were effective in controlling the disease, and there were no significant differences among the substrates. According to the results of this study, broom sorghum grain, rice husk, rice straw, sugar beet pulp and cow dung could be recommended as suitable fermentation media for the industrial-scale production of T. harzianum strains.

Experimental study and numerical simulation of mean longshore current for mild slope

In this paper, experimental and numerical studies were performed to investigate the characteristics of longshore current under two mild slopes, the results of which may complement the existing studies, which have mainly focused on steep slopes. The experimental results revealed that the average velocity distribution of the longshore current was significantly different under the two different mild slopes. Under the slope of 1:100, the distribution of the averaged longshore current velocity had a downward concave trend at the nearshore side, while under the slope of 1:40 the trend became convex. In addition, the analysis of the numerical results showed that the distribution of the averaged longshore current velocity was affected by the distribution of the wave height within the surf zone and the bottom friction equations, with the influence of the latter being more significant. For the slope of 1:100, the cross-shore variability of alongshore variability can be calculated using the flow-type bottom friction equation, while for the slope of 1:40, the wave-type bottom friction equation can be used instead. Finally, the secondary breaking wave heights for mild slopes and the distribution of wave set-up are also shown in the study.

Wave-by-Wave Forecasting via Assimilation of Marine Radar Data

AbstractThis work describes a phase-resolving wave-forecasting algorithm that is based on the assimilation of marine radar image time series. The algorithm is tested against synthetic data and field observations. The algorithm couples X-band marine radar observations with a phase-resolving wave model that uses the linear mild slope equations for reconstruction of water surface elevations over a large domain of O(km) and a prescribed time window of O(min). The reconstruction also enables wave-by-wave forecasting through forward propagation in space and time. Marine radar image time series provide the input wave observations through a previously given relationship between backscatter intensity and the radial component of the sea surface slope. The algorithm assimilates the wave slope information into the model via a best-fit wave source function at the boundary that minimizes the slope reconstruction error over an annular region at the outer ranges of the radar images. The wave model is then able to propagate the waves across a polar domain to a location of interest at nearer ranges. The constraints on the method for achieving real-time forecasting are identified, and the algorithm is verified against synthetic data and tested using field observations.

Evaluation of geomorphologic similarity between the sub-catchments of Cauvery river basin

Estimation of morphometric indices can be useful in defining similarity relationships between catchments over a wide range of scales and it facilitates the effective understanding of hydrogeologic processes. This study aims at evaluating morphometric parameters to investigate geomorphologic similarity between the sub-catchments of the Cauvery river basin which is a major river basin in Peninsular India. The Digital Elevation Model (DEM) obtained from Shuttle Radar Topographic Mission (SRTM) at 30 m spatial resolution is used for assessing the linear, areal and relief aspects of morphometric analysis. The stream network analysis of sub-catchments reveals that the basin is dominated by streams of lower order and the Cauvery basin can be characterized as a seventh order basin. Linear parameters indicate that the basin is subjected to less structural disturbances. Assessment of areal parameters shows that most of the sub-catchments have elongated shape, low drainage density and course drainage texture. Evaluation of relief parameters suggests that the sub-catchments have mild slopes with moderate ruggedness and resistant soil surface. The sub-catchments are found to be geomorphologically similar in behaviour and this analysis can throw insight on development of scaling relationships as well as hydrological predictions in ungauged areas of the drainage basin.

Short-Term and Long-Term Solutions of Two-Dimensional Shallow Water Equations Using the Modified Decomposition Method

In this paper, two modifications of the decomposition method (DM) including its multistage form (say here MSDM) and its combination with the Pade approximants (say here DMPA) are proposed and applied for the short-term and long-term solutions of two-dimensional shallow water equations (SWEs) including friction effects. Due to nonlinear behavior of the model, the DM is used to facilitate the computations on the nonlinear terms. However, the MS technique is used to obtain a solution for longer periods of time and to prevent accuracy issues associated with the standard DM at large times. The results of the proposed method are compared with those obtained using the PAs as an after treatment technique which also yields an accurate solution in our work. It has been shown that the MS technique can efficiently be used in the solution of the nonlinear coupled SWEs and would extend the domain of validity of the solution obtained via the standard DM. However, the necessity of predicting the long-term behavior of flow in some applications makes the PAs superior to the MS technique with respect to accuracy and CPU time. Numerical and graphical results of the flow characteristics for a given application of two-dimensional flood wave over two types of mild and steep slopes are presented to elucidate the efficiency of the proposed modifications in the study of the flow behavior. Moreover, a convergence analysis and the time evolution of the residuals as an index of the solution error are also presented in tabular and graphical forms.

Instability and cross-boundary-layer transport by shoaling internal waves over realistic slopes

Internal solitary and solitary-like waves (ISW) play an important role in mixing and sediment resuspension in naturally occurring stratified fluids, primarily through various instabilities and wave-breaking mechanisms. When shoaling into shallow waters, waves of depression may either fission into a packet of waves of elevation over mild slopes or break over steep slopes. The fissioning process is generally considered a less efficient transport and resuspension mechanism, compared to wave breaking, since very little turbulent mixing or energy dissipation occurs during this process. In the present work, however, we found that this is not always the case, at least in the particular context of ISW boundary-layer interaction. Using high-resolution numerical simulations performed in a domain representing a tilted laboratory tank, we found that boundary-layer instability in the form of a separation bubble consistently occurs during the fissioning process. The separation bubble is generated beneath the wave of elevation that emerges from the fissioning process, and is vitally influenced by currents induced by the leading wave of depression. As the waves shoal further, the growth and breakdown of the separation bubble leads to significant cross-boundary-layer transport. The results suggest that the fissioning process, which occurs over a considerable geographical region in the ocean, can be as efficient as wave breaking when it comes to cross-boundary-layer transport.

Analytical Solution of Extended Mild Slope Equation for Waves Propagation over Axi-symmetric Pit

Analytical Solution of Extended Mild Slope Equation for Waves Propagation over Axi-symmetric Pit

Contrasting patterns of native and non-native plants in a network of protected areas across spatial scales

Networks of protected areas are fundamental for biodiversity conservation, but many factors determine their conservation efficiency. In particular, on top of other human-driven disturbances, invasions by non-native species can cause habitat and biodiversity loss. Jointly understanding what drives patterns of plant diversity and of non-native species in protected areas is therefore a priority. We tested whether the richness and composition of native and non-native plant species within a network of protected areas follow similar patterns across spatial scales. Specifically, we addressed three questions: (a) what is the degree of congruence in species richness between native and non-native species? (b) do changes in the composition of non-native species across ecological gradients reflect a similar turnover of native species along the same gradients ? (c) what are the main environmental and human disturbance drivers controlling species richness in these two groups of species? Species richness and composition of native and non-native plant species were compared at two spatial scales: the plot scale (10 m × 10 m) and the Protected Area scale (PA). In addition, we fit Generalized Linear Models to identify the most important drivers of native and non-native species richness at each scale, focusing on environmental conditions (climate, topography) and on the main sources of human disturbance in the area (land use and roads). We found a significant positive correlation between the turnover of native and non-native species composition at both plot and PA scales, whereas their species richness was only correlated at the larger PA scale. The lack of congruence between the richness of native and non-native species at the plot scale was likely driven by differential responses to fine scale environmental factors, with non-natives favoring drier climates and milder slopes (climate and slope). In addition, more non-native species were found closer to road-ways in the reserve network. In contrast, the congruence in the richness of native and non-native species at the broader PA scale was mainly driven by the common influence of PA area, but also by similar responses of the two groups of species to climatic heterogeneity. Thus, our study highlights the strong spatial dependence of the relationship between native and non-native species richness and of their responses to environmental variation. Taken together, our results suggest that within the study region the introduction and establishment of non-native species would be more likely in warmer and dryer areas, with high native species richness at large spatial scale but intermediate levels of anthropogenic disturbances and mild slope inclinations and elevation at fine scale. Such an exhaustive understanding of the factors that influence the spread of non-native species, especially in networks of protected areas is crucial to inform conservation managers on how to control or curb non-native species.

Strength Parameters of Stabilized Clay Using Polypropylene Fibers and Nano-MgO: An Experimental Study

In this study, the effect of two additives, including recycled polypropylene (PP) fibers and Nano magnesium oxide (MgO), was investigated in the improvement of strength characteristics of clay. Some samples of clay, with or without additives, were prepared and strength characteristics were measured by unconfined compression and direct shear tests. The soil was stabilized by adding 0.2%, 0.5% and 1% of PP fiber and/or 0.2%, 0.4%, 0.8% and 1% of nano-MgO by dry weight of the soil. The results of the unconfined compression tests show that nano-MgO can significantly increase the stiffness of the soil and the undrained cohesion of the clay. Adding 0.2% nano-MgO raises the undrained cohesion about 45%. However, the undrained cohesion slows down to a mild slope after adding more nanomaterial. The direct shear test also demonstrates the significant increase of internal friction angle of the samples with PP fibers and implies proper engagement of the PP fibers within the reinforced soil structure. Besides the increase of the stiffness, adding the fibers increases the ductility of the samples and imparts more failure strain. The study of scanning electron microscope also shows that the nanomaterial has significantly turned clay particles from the layered sheet structures into concentrated ones and created a behavior like granules as far as the internal friction of clay is concerned. Moreover, these conditions and development of a hard mass of nano-soil can provide more interlocking with the fibers due to the pressure from compression and surcharge loading. It therefore increases the strength and mass interlocking and controls the strains in the sample.

Variation of Groundwater Flow Caused by Any Spatiotemporally Varied Recharge

The objective of this study was to develop a complete analytical solution to determining the effect of any varying rainfall recharge rates on groundwater flow in an unconfined sloping aquifer. The domain of the unconfined aquifer was assumed to be semi-infinite with an impervious bottom base, and the initial water level was parallel to the impervious bottom of a mild slope. In the past, similar problems have been discussed mostly by considering a uniform or temporally varying recharge rate, but the current study explored the variation of groundwater flow under temporally and spatially distributed recharge rates. The presented analytical solution was verified by comparing its results with those of previous research, and the practicability of the analytical solution was validated using the 2012 and 2013 data of a groundwater station in Dali District of Taichung City, Taiwan.

Unlined trench as a falling head permeameter: Analytic and HYDRUS2D modeling versus sandbox experiment

An isosceles triangle in a vertical cross-section of a trench is considered as a boundary from which free water in the trench seeps into a porous bed. A finite, initially impounded water volume vanishes from the channel and soil moisture moves in conjugation with surface water in a transient 2-D saturated-unsaturated regime. If capillarity is ignored and the subjacent soil is assumed to be dry before filling the channel, then a wetting front propagates as a sharp interface mated with drawdown of the channel free water. A Lembke method of consecutive steady states is used to model the interface as a rotating straight-line. A zone of Darcian seepage is a triangle, three sides of which (at each time instance) are a streamline, a constant piezometric head line and isobar. The instantaneous hinge point of the interface demarcates a zone of imbibition from a zone of drainage of this saturated triangle. Mathematically, a Green-Ampt type nonlinear first order ODE is obtained and explicitly integrated by separation of variables and the drawdown time t is explicitly expressed through the water depth H in the trench. In a sandbox with a dune sand, an experimental H(t) is measured in a trench having mild and steep bank slopes. When H(t) > 0 the drawdown rate increases that is attributed to an increase of the effect of capillarity. For this stage, Riesenkampf’s analytical solution for steady 2D tension-saturated flow with a capillary fringe is used. The analytical and experimental results are compared with those obtained by HYDRUS-2D (numerical modeling), involving a reservoir boundary condition introduced for furrow irrigation applications. Model performance parameters including the root mean squared error (RMSE), mean absolute error (MAE), coefficient of determination (r2) and Nash-Sutcliffe efficiency (E) showed a good agreement between the measured and simulated values of drawdown time. Results of the t-test between the measured and simulated drawdown time showed insignificant differences at a 5% confidence interval for all the trenches (p > 0.05). HYDRUS simulations quantified the dynamics of a “sinking” saturated “bubble” under the trench: isobars, isotachs, streamlines and loci of the stagnation points are plotted. We illustrate how to use a drawdown curve H(t) for determination of saturated hydraulic conductivity and air-entrance pressure in the Vedernikov-Bouwer model.

Experiments, analytical and HYDRUS2D modeling of steady jet of quasi-normal surface flow in rectangular channel coupled with vertical seepage: Vedernikov-Riesenkampf's legacy revisited

Channels are widely used for conveying natural flash floods or managed aquifer recharge (MAR) released treated wastewater. Adequate models are needed for describing the interaction between hydraulics of surface flow downslope the channel and vertical seepage into a porous bed for evaluation of the depth of water and the length to which surface water “jet” propagates over a porous bed. Experiments with surface “jets” (consumed by bed infiltration) are compared with numerical and analytical modeling of these coupled flows. In the field (Al-Hail site, Oman), at a pedestal and slope of a dune, two rectangular trenches had a sand bed and a mild and steep slope S (3° and 25°, correspondingly). After applying constant discharges at the inlet of the trenches, the length, L, of the water “jets” propagating until complete extinction has been measured. The wetting front into the subjacent sand has been detected by measuring the volumetric soil moisture content at different depths in an excavation, immediately after termination of discharging the surface water. Analytically (by the hodograph method), 2-D steady phreatic seepage flow from a rectangular channel was examined as a special case of Vedernikov's solution for a soil without capillarity. Since the depth of water was small, the Riesenkampf analytical solution, involving capillarity in the tension-saturated flanks of the channel, has been also utilized. Numerically, Richard's equation has been solved by a finite element method, HYDRUS2D for arbitrary soils. The boundary condition was a hydrostatic pressure head along the wetted perimeters of the channels with water depth gradually dropping downslope. Coupling of surface and subsurface flows has been done by the “kinematic waves” approximation with Manning's friction slope equal to S. In the ODE for conservation of mass, the sink term (infiltration) was computed by either HYDRUS or analytical solution. The corresponding boundary value problem was solved by computer algebra routines.

Influence of Mild Bottom Slopes on the Overtopping Flow over Mound Breakwaters under Depth-Limited Breaking Wave Conditions

The crest elevation of mound breakwaters is usually designed considering a tolerable mean wave overtopping discharge. However, pedestrian safety, characterized by the overtopping layer thickness (OLT) and the overtopping flow velocity (OFV), is becoming more relevant due to the reduction of the crest freeboards of coastal structures. Studies in the literature focusing on OLT and OFV do not consider the bottom slope effect, even if it has a remarkable impact on mound breakwater design under depth-limited breaking wave conditions. Therefore, this research focuses on the influence of the bottom slope on OLT and OFV exceeded by 2% of incoming waves, hc,2% and uc,2%. A total of 235 2D physical tests were conducted on conventional mound breakwaters with a single-layer Cubipod® and double-layer rock and cube armors with 2% and 4% bottom slopes. Neural networks were used to determine the optimum point to estimate wave characteristics for hc,2% and uc,2% calculation; that point was located at a distance from the model toe of three times the water depth at the toe (hs) of the structure. The influence of the bottom slope is studied using trained neural networks with fixed wave conditions in the wave generation zone; hc,2% slightly decreases and uc,2% increases as the gradient of the bottom slope increases.

An efficient Navier-Stokes based numerical wave tank using fast Poisson solvers and the immersed boundary method

An efficient numerical model for wave induced flows and their interaction with impermeable coastal structures, is presented. Using recent developments in the field of two-fluid (water/air) Navier-Stokes (NS) simulations, an efficient numerical wave tank (NWT) was developed which combines the Immersed Boundary (IB) method and Fast Direct Solvers (FDS). Conventional NS-based NWTs require significant computational resources which prevents their use in discretisation demanding cases or extensive parametric studies. The computational efficiency of the new NWT was achieved by replacing the conventional variable-coefficient Poisson equation with a constant-coefficient one which is solved with a FDS. Results of the accuracy, limitations, and computational performance of the NWT are presented and discussed based on several validation tests: (1) propagation of a 2nd-order Stokes wave, (2) formation of a standing wave, (3) spilling breaking over a mild slope bed, (4) three-dimensional (3D) interaction of a solitary wave with a vertical abutment, and (5) diffraction of a solitary wave by a single-row pile breakwater. The computational performance of the new NWT was demonstrated for problems with 1–280 million grid nodes. The overall speed-up of the new NWT increases with the problem size, and it is estimated to be about 30 for large 3D problems.

Temporal instability of soil moisture at a hillslope scale under subtropical hydroclimatic conditions

Temporal instability, a condition of soil moisture with unstable spatiotemporal patterns, may occur when the relative roles of the controlling factors change. It impacts the applicability of the temporal stability in the prediction of soil moisture. However, the occurring frequency, degree and underlying hydrological conditions of the temporal instability are far from clear. This study aimed to examine the presence of temporal instability at the hillslope scale and to characterize and quantify the frequency, degree and underlying hydrological conditions contributing to the phenomenon. Sloping crop lands under subtropical hydrological conditions are known for their frequent transition between dry and wet periods and were chosen for this study. Soil moisture was monitored at 5 locations and at seven soil depths down to 2.2 m along a 160 m hillslope over a period of a year. Relative difference analysis was employed to evaluate the temporal stability of soil moisture. Representative locations (RLs) mainly appeared at locations with a mild slope and relatively high sand content. Daily RLs were not consistent among the study period, which has the highest proportion to be the same to those full dataset based. These proportions were depth dependent, the lowest (40%) at moderate soil layers (i.e. 50 and 80 cm) and the highest (95%) at deep soil layers (i.e. 180 and 220 cm). An obvious temporal instability was observed by the extensive ranges in the daily mean relative difference (MRD) values. If the whole dataset was used to calculate the mean soil moisture of the hillslope, it would be overestimated by 16.1% or underestimated by 18.2%. The frequency of temporal instability was low and varied over time and soil depths. For example, 17% of the time for this period was temporally unstable at 20 cm and 2% time of the study period was unstable at 220 cm. These low proportions confirm that the temporal stability remains a valid and robust tool in mean soil moisture prediction. The rainfall after a long drought period or a storm after successive rainfall probably caused the temporal instability. Therefore, caution should be exercised during the strong dry-wet transition period.

Applying Biomineralization Technology to Study the Effects of Rainfall Induced Soil Erosion

The rainless days and drought seasons reveal a tendency to lengthen the wet and dry period in recent years in Taiwan. In the bare riverbeds in central Taiwan, such as the Dajia and Zhuoshui rivers, fugitive dust is the common problem during the winter’s dry period with northeast monsoon. The study aims to use the biological method, Microbial-induced carbonate precipitation (MICP), to solidify the soil and implement a series of rainfall simulator experiments to reduce the Aeolian dust emission problems. Accordingly, the relationship between rainfall-induced soil erosion and its soil specimens are also discussed. The soil conducted the MICP for seven days as the curing age, and then be analyzed the degree of soil solidification under different conditions, rainfall intensity of 41 mm/h and 61 mm/h by the soil erosion experiment. The effect of soil solidification with various relative density of soils of 60%, 70%, and 80%, and hillside slopes of 5°, 10°, 20° were tested. The result indicated that, the higher the relative density of soils, the better the effect of soil solidification would be. The relative density of soils from 60% to 80% all kept the effect of soil solidification as applying to MICP. Therefore, it was important to select the curing age with the matching relative density of soils. Moreover, the most appropriate condition for the effects of soil solidification by MICP was the slopes below 10° and the curing age for seven days. The effect of soil solidification was still preserved in that with the high intensity rainfall (66 mm/h) due to the Aeolian dust emission commonly happening in the bare riverbeds with mild slopes.