Sazia Afreen

Saitama University , Japan, Civil and Environmental Engineering, Graduate Student

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Climate Change Impacts on Rain Water Harvesting Potential In Bangladesh

iwanews.org

Rainwater harvesting (RWH) in response to climate extremes enhances the resilience of human socie... more

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Three Dimensional Downstream Scour Analysis After Levee Overtopping

Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

Three dimensional experiments are conducted to analyze the downstream scour dimensions after leve... more Three dimensional experiments are conducted to analyze the downstream scour dimensions after levee overtopping. For elucidating the difference of scour dimension under various hydraulic (overtopping flow height at the levee top, d bank) and geometric parameters (levee height, h bank , overtopping flow width along the levee, W bank), 3D scour profiles are investigated. From the analysis, it has been observed that at equilibrium conditions, for the same d bank cases scour depth (S d) is higher for greater h bank (10cm) compared with lower levee height (6cm). In contrast, scour length (S l) is longer in case of lower h bank compared to higher h bank for same d bank. The stronger hydraulic jump that took place in case of smaller levee height cases appears to play a significant role in developing greater scour length along with shorter scour depth. Three separate equations for S d , S l and S w (scour width) have been proposed from multiple regression analysis. These results can be useful for the study of levee design.

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Effect of Submergence Condition and Overtopping Depth on Gully Scour Dimensions: Observations from the 2011 Great East Japan Tsunami

Journal of Earthquake and Tsunami, 2016

When a tsunami reaches a shore, it propagates along river channels with tremendous energy and ove... more When a tsunami reaches a shore, it propagates along river channels with tremendous energy and overtops river levees. It causes severe damage to the levee structures through scouring along levee slope. In the present study, gully scours created along the levee slopes of two rivers (Omotogawa and Sakarigawa Rivers) in Iwate Prefecture and three rivers (Nanakitagawa, New Kitakamigawa, and Abukumagawa Rivers) in Miyagi Prefecture were investigated after the 2011 Great East Japan tsunami. The energy head during levee overtopping for each location was calculated from post-tsunami surveys. The relationship between the energy head and gully scour dimensions (length, width, and depth) was analyzed. The analyses clarified that gully scour dimensions were greatly dominated by two important phenomena: (i) overflow type (free overflow or submerged overflow), and (ii) soil texture at the scoured region. The present study results can be utilized to obtain the overtopping flow height for post-tsuna...

Investigation of Scour Pattern Downstream of Levee Toe Due to Overtopping Flow

Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 2015

Levee overtopping creates large scoured region at the landside, which greatly affects the levee p... more Levee overtopping creates large scoured region at the landside, which greatly affects the levee performance. Both 3D and 2D experiments were conducted to analyze the downstream scour profile after levee overtopping. For elucidating the difference of scour pattern under various overtopping water depth and width conditions, 3D scour profiles are investigated. In addition, vertical 2D scour profiles are also investigated to compare the 3D scour profiles with 2D experiment results. From the analysis, it has been observed that for overtopping width (W bank) to levee height (h bank) ratio of 6 to 8, multiple scour holes appear with overtopping height (d bank) to levee height (h bank) ratio of 0.1 to 0.2, while for same W bank /h bank , two scour holes are created when d bank /h bank =0.25 to 0.3. Comparison of 2D and 3D scour data sets at downstream scour profiles shows that 3D experiments tend to create larger scour depth and shorter scour length than 2D cases. This result indicates the importance of 3D experimental analysis for levee design. .

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Geometrical Characteristic of Scour Holes Caused by Overtopping Flow of Embankment Covered with Different Lengths of Protection Works

Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 2015

Scouring downstream of hydraulic structures is a complex phenomenon that causes the instability a... more Scouring downstream of hydraulic structures is a complex phenomenon that causes the instability and even the failure of the structures. This experiment-based research was conducted to study the effect of the protection work length, L, along the embankment landside slope on the relationship between non-dimensional scour depth (S D /Lsinθ) and its location (S P /Lcosθ) under various overtopping flow depths (S D : maximum scour depth, S P : the location of S D , and θ: the landside slope angle). For evaluating the possibility of the fragility of the embankment landside slope, a schematic diagram based on the angle of repose of foundation behind embankment toe is proposed in this study. The result shows that the effect of the protection work length on the risk of the embankment landside slope fragility are classified into 3 types according to the variation of the overtopping flow depths.

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Adaptation to Climate Change Impacts through Rain Water Harvesting for Agriculture of Bangladesh

Contribution of Rainwater in Meeting Crop Water Requirement in context of Climate Change Impacts

Potential of Rainwater Harvesting in Dhaka City

Water resources are fast depleting in urban areas due to rapid increase in population and unrestr... more Water resources are fast depleting in urban areas due to rapid increase in population and unrestricted use of water. Optimization of water usage and the conservation of water as a natural resource can help to overcome water shortage. This study focuses on the potential of Rain Water Harvesting (RWH) in Dhaka City. At first, long term rainfall analysis of Dhaka has been done. Analyses of rainfall data show that average rainfall of 55 years (1953-2007) in Dhaka is 2073 mm, whereas the same for recent 12 years (1996-2007) is 2166 mm. Decadal rainfall analysis considering rainfall data of 55 years for five consecutive decades (50s, 60s, 70, 80s and 90s) and for the period of 2000 to 2007 shows an increasing trend of rainfall in the recent decades. From the mass curve (rain water availability vs. time) analysis of Dhaka city, it is found that maximum 0.38m 3 of water deficit occurs during the month of April on the other hand 0.25m 3 of maximum excess water is available during October. In this study, contribution of rainwater in meeting water demand of Dhaka city has also been analyzed. Results show that 33% water demand can be met through RWH with individual harvesting system and 10% water demand can be met with community based RWH system. Finally from roof size distribution of different wards of Dhaka city, a method has been presented using GIS to identify the potential areas where RWH can be adopted for partial fulfillment of water demand. These analyses suggest that, in Dhaka, RWH system can be used in conjunction with conventional water supply system to improve the present water scarcity.

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