Babar Mujtaba

This study investigates the impact of a submerged trapezoidal broad-crested (TBC) weir on local scouring around a uniform single circular bridge pier under clear-water flow conditions. The TBC weir was installed downstream of the pier, and its effectiveness was evaluated based on variations in separation distance and weir height. The results indicated that the presence of the TBC weir significantly reduced the scour depth and altered the geometry of the scour hole. The impact of the TBC weir was most pronounced when the separation distance between the pier and weir was minimal. Three different weir heights were analyzed to determine the optimal configuration for scour mitigation. Additionally, this study identifies the threshold distance beyond which the influence of TBC weirs on scour mitigation becomes negligible. The findings reveal that the maximum scour reduction of 69.57% occurs when the TBC weir height-to-water depth ratio (Z/h) and separation distance (S) are 0.47 and 0, respectively, where the pier and weir are in direct alignment.

A one-dimensional numerical overland flow model based on the cascade plane theory was developed to estimate rainfall-induced runoff and soil erosion on converging and diverging plane surfaces. The model includes three components: (i) soil infiltration using Horton’s infiltration equation, (ii) overland flow using the kinematic wave approximation of the one-dimensional Saint-Venant shallow water equations for a cascade of planes, and (iii) soil erosion based on the sediment transport continuity equation. The model’s performance was evaluated by comparing numerical results with laboratory data from experiments using a rainfall simulator and a soil flume. Four independent experiments were conducted on converging and diverging surfaces under varying slope and rainfall conditions. Overall, the numerically simulated hydrographs and sediment graphs closely matched the laboratory results, showing the efficiency of the model for the tested controlled laboratory conditions. The model was then used to numerically explore the impact of different plane soil surface geometries on runoff and soil loss. Seven geometries were studied: one rectangular, three diverging, and three converging. A constant soil surface area, the rainfall intensity, and the slope gradient were maintained in all simulations. Results showed that increasing convergence angles led to a higher peak and total soil loss, while decreasing divergence angles reduced them.

A one-dimensional numerical overland flow model based on the cascade plane theory was de-veloped to estimate rainfall-induced runoff and soil erosion on converging and diverging plane surfaces. The model includes three components: (i) soil infiltration using Horton’s infiltration equation, (ii) overland flow using the kinematic wave approximation of the one-dimensional Saint-Venant shallow water equations for a cascade of planes, and (iii) soil erosion based on the sediment transport continuity equation. The model’s performance was evaluated by comparing numerical results with laboratory data from experiments using a rainfall simulator and a soil flume. Four independent experiments were conducted on converging and diverging surfaces under var-ying slope and rainfall conditions. Overall, the numerically simulated hydrographs and sediment graphs closely matched the laboratory results, showing the efficiency of the model for the tested controlled laboratory conditions. The model was then used to numerically explore the impact of different plane soil surface geometries on runoff and soil loss. Seven geometries were studied: one rectangular, three diverging, and three converging. Constant soil surface area, rainfall intensity, and slope gradient were maintained in all simulations. Results showed that increasing convergence angles led to higher peak and total soil loss, while decreasing divergence angles reduced them.

Pakistan is facing an epidemic of dengue fever amidst COVID-19 outbreak which is a serious public health concern. This article provides an overview of factors that could have led to an unexpectedly higher number of Dengue fever cases in Pakistan this year, such as, insufficient preventive measures to control Dengue at the national and domestic level, lack of surveillance system for the spread and control of the disease, and the lack of awareness among the general population regarding the possible outbreak of the disease. This situation has challenged the overburdened healthcare system of the developing country, which was still recovering from the immense pressure of COVID-19. This study also highlights the challenges faced by physicians regarding the diagnosis and treatment of patients who are coinfected with COVID-19 and Dengue fever. Early detection and accurate diagnosis are crucial for the management of patients with either of the disease. Authors have suggested a few measures that may help in improving the management and prognosis of patients coinfected with COVID-19 and Dengue fever. Additionally, we have also proposed a few strategies, that, if adapted at the national level may help in controlling the spread of Dengue fever in the future. For example, policies should be devised by the government for the implementation of preventive measures at the domestic level which was in practice before the outbreak of COVID-19.

The role of stony soils in runoff response of mountain catchments is rarely studied. We have compared simulated response of stony soils with measured catchment runoff for events caused by rains of small and high intensities in the mountain catchment of the Jalovecký Creek, Slovakia. The soil water response was simulated for three sites with stoniness 10–65% using the Hydrus-2D single porosity model. Soil hydraulic parameters employed in the modelling, i. e. the saturated hydraulic conductivity and parameters of the soil water retention curves, were obtained by two approaches, namely by the Representative Elementary Volume approach (REVa) and by the inverse modelling with Hydrus-1D model (IMa). The soil water outflow hydrographs simulated by Hydrus-2D were compared to catchment runoff hydrographs by analysing their skewness and peak times. Measured catchment runoff hydrographs were similar to simulated soil water outflow hydrographs for about a half of rainfall events. Interestingly, most of them were caused by rainfalls with small intensity (below 2.5 mm/10 min). The REV approach to derive soil hydraulic parameters for soil water outflow modelling provided more realistic shapes of soil water outflow hydrographs and peak times than the IMa approach.

Soil erosion in the presence of surface rock fragments and organic mulches has been mostly studied for 1-dimensional surface flows. This study evaluates the influence of different distribution patterns of rock fragment surface cover on runoff and soil loss from converging and diverging plane surfaces. The laboratory apparatus was comprised of a rainfall simulator and a soil flume, which geometry was based on a circular sector, of 2.02 m length and limited by 0.10 m and 2.10 m arc lengths. The soil flume had runoff collection outlets at both ends in order to perform experiments on both converging and diverging plane surfaces. Rainfall events with a mean intensity of 87 mm hr^–1 and duration of 10 min were simulated at a 20% slope gradient for six scenarios on both soil surfaces’ geometries. These scenarios were (i) control (bare soil), (ii) three distribution patterns (i.e., evenly diamond distributed, line rows and radial rows) of 40% rock fragment surface cover, (iii) organic mulch over bare soil and (iv) organic mulch over rock fragment surface cover. Results indicate that all tested rock fragment surface cover patterns increased runoff volumes and soil loss with respect to control scenario while mulch cover scenarios decreased runoff and soil loss. Diamond pattern rock fragment cover scenario caused the largest increase and the radial rows pattern the least increase compared to the control scenario, on both converging and diverging surfaces. For all six scenarios, soil loss on a converging surface was ~10–30 times higher than on the diverging surface. Our study suggests that soil surface geometry had more influence on soil erosion than different distribution patterns of specific percentage of rock fragment surface cover, in part due to flume’s border effect.

Application of crop residues (mulch) over the soil surface is a common practice to control soil erosion and promote infiltration. This laboratory study aimed at investigating the effect of different rice straw mulch sizes on runoff and sediment transport. The experimental runs were conducted using a soil flume of adjustable slope and a rainfall simulator, considering bare soil and three different soil covers: 1, 2 and 5 t ha⁻¹ application rates, for three sizes of rice straw mulch (10, 30 and 200 mm). The experimental results showed that for the same mulch application rate (by weight), the smaller mulch sizes (i.e. high surface coverage percentage) presented less soil loss. For example, 90 % soil loss reduction was achieved for smaller sizes of rice straw mulch and 80 % for the bigger size. The results of this study are an important contribution to the understanding of the soil loss process in small basins and to the definition of relevant soil conservation measures, at the plot/field scale.