Effects of sediment deposit on the hydraulic performance of the urban stormwater drainage system

Sediment deposit is a critical factor strongly affecting the drainage capacity of the conduits due to its cross-section area narrowing and roughness increasing. In this study, a numerical model was applied to investigate the influences of sediment deposit on the hydraulic performance of the drainage conduits. The Nhieu Loc - Thi Nghe (NL-TN) basin, located in Ho Chi Minh City, Vietnam, was selected as a case study. The drainage network of the NL-TN basin was simulated by using the EPA-SWMM model. The effects of sediment deposit were assessed by a non-dimensional comparison of the simulated peak flows of the sediment-deposited conduits and the clean ones. The results indicated that the sediment deposit significantly affects the flow capacity of the conduits and could cause severe inundation. Narrowing of the cross-section area has more impact on the hydraulic performance of the conduit than the increase in the roughness. A 40% increase in the Manning coefficient could decline the peak flow to approximately 80-90%, while a 40% increase in sediment thickness depth could degrade the peak flow by about 60-70% to compare with the peak flow of the clean conduit. The findings could support decision makings on the operation and maintenance of the sewer system and adaptation to extreme rainfall events.

Subsurface Sediment Deposits of Tanjung Berikat Coast, Bangka, Determined from GPR Interpretation

Tanjung Berikat Coast in Central Bangka, is a part of the Southeast Asian tin belt. We conducted four Ground-Penetrating Radar (GPR) survey lines and 13 hand auger coring to understand sediment deposition and composition. Two similar units were determined from GPR lines BLG 01–BLG 03: Unit A at the top part, reflected by parallel and continuous reflector configuration, weak–strong electromagnetic wave. Underneath Unit A is Unit B, characterized by subparallel configuration, not continuous–chaotic, weak–medium electromagnetic wave. Unit B is absent in BLG 04. We identify another two units from BLG 04 and BLG 03, Unit C, characterized by subparallel reflector configuration, not continuous– chaotic, weak–strong electromagnetic wave. It exhibits distinctive modulating contact with Unit D. Unit D is characterized by chaotic reflector configuration, relatively stronger electromagnetic wave that might be correlated to the granite intrusion Tanjung Klabat. Sediment deposit is composed of fine–coarse sand, consisting mostly of clastic plutonic and clastic biogenic (coral and mollusk fragments), which increase downward. This indicates marine-fluvial influence, which suggests that sea-level changes strongly influence sedimentation process. Unit A from GPR is correlated to these sediment deposits, the other three units might be correlated to weathering of older insitu deposit.

Sediment Thickness Estimation in Serpong Experimental Power Reactor Site Using HVSR Method

A study about sediment thickness mapping was conducted in Serpong Experimental Power Reactor Site. This reactor is planned to be built in a high seismic activity area. Sediment thickness is one of many factors that could affect the site response. A high sediment deposit could amplify and prolong the earthquake waves. This condition could make the reactor building more vulnerable to seismic hazard. The sediment thickness was estimated using the microtremor HVSR method. The parameter used for sediment thickness calculation was obtained from the borehole and cross-hole seismic survey and was tested to ensure that the chosen parameter and the method were accurate. The deviation found in the borehole data was also calculated to determine the accuracy level of the calculation. The current planned location for the reactor is in a relatively low sediment deposit area with 8.8 m of thickness, however there is an area, west of the current location that might be a better location for the reactor based on the result of this study.

Experimental Investigation of Erosion Characteristics of Fine-Grained Cohesive Sediments

In this short communication, the erosion process of the fine, cohesive sediment collected from the upper River Taw in South West England was studied in a rotating annular flume located in the National Water Research Institute in Burlington, Ontario, Canada. This study is part of a research project that is underway to model the transport of fine sediment and the associated nutrients in that river system. The erosion experimental data show that the critical shear stress for erosion of the upper River Taw sediment is about 0.09 Pa and it did not depend on the age of sediment deposit. The eroded sediment was transported in a flocculated form and the agent of flocculation for the upper River Taw sediment may be due to the presence of fibrils from microorganisms and organic material in the system. The experimental data were analysed using a curve fitting approach of Krone and a mathematical model of cohesive sediment transport in rotating circular flumes developed by Krishnappan. The modelled and measured data were in good agreement. An evaluation of the physical significance of Krone’s fitting coefficients is presented. Variability of the fitting coefficients as a function of bed shear stress and age of sediment deposit indicate the key role these two factors play in the erosion process of fluvial cohesive sediment.

TECHNOLOGY IMPROVEMENT OF HIGH-DISPERSIVE METALLIC IRON POWDERS BASED ON SEDIMENTS OF IRON REMOVAL STATION

Sediments from iron removal stations are a source of environmental pollution. It is necessary to find effective and eco-friendly methods of sediment disposal. The paper investigates the properties of iron-containing sediment in order to develop a technology for its further utilization. It is shown that sediments from the iron removal station of Velizhansky water intake have a stable chemical composition with about 70 % Fe2O3, and a stable particle size distribution, i.e. 20 μm for ≈ 87 % of particles. These parameters allow developing a flow chart for iron reduction in heated carbon monoxide. The involvement of sediments from iron removal stations in the high-dispersive metallic iron powder production eliminates the sediment deposit at landfills or storage tanks and creates a new raw material base for additive technologies.

The Utilization of Regression and Analysis of Variance to Model Hurricane Storm Surge Sedimentation on Coastal Marshes along the Northern Gulf of Mexico Coastline

<p>Coastal marshes along the northern Gulf of Mexico coastline provide very important ecosystem services such as serving as habitat for a variety of flora and fauna and providing flood protection for inland areas. A growing body of research has documented how hurricane storm surge sedimentation has increased the elevation of coastal marshes along the northern Gulf of Mexico coastline. This study investigates spatial variations in sediment distribution on McFaddin National Wildlife Refuge, Texas, USA, which is in the geographic region that was impacted by the right-front quadrant of Hurricane Ike. This research builds upon a prior study on hurricane storm surge sedimentation in which the sediment deposits from hurricanes’ Audrey, Carla, Rita, and Ike were identified on a marsh transect on McFaddin National Wildlife Refuge. The purpose of this study was to discover how hurricane storm surge sedimentation spatially varies in relation to the landfall location of Hurricane Ike. Fieldwork conducted in 2017-2018 involved digging shallow pits on four coastal marsh transects between Sabine Pass, Texas and High Island, Texas. Elevations were measured at each pit site along all four transects using a telescopic lens and stadia rod. The transects extend 880-1630 meters, with pit sites beginning near the coastline and extending landward. Results obtained in the field indicate that the Hurricane Ike sediment deposit has been found on all four transects, and that the deposit decreases in thickness moving landward along each transect. Furthermore, the observational results of this study were used in Regression Analyses to model hurricane storm surge sediment deposit thickness based on pit site distance inland, pit site elevation, and distance from the landfall of Hurricane Ike. Moreover, Analysis of Variance revealed whether distance inland, distance from landfall location, and the interaction between distance inland and distance from landfall location had any significant effect on storm surge deposit thickness. Actual sediment deposit thicknesses measured in the field were compared to the Regression and Analysis of Variance results. Results show that the Power Law Curve from the Regression Analyses was the most robust predictor of pit site sediment thickness based on distance inland, with an R<sup>2</sup> value of 0.538. Additionally, the Regression and Analysis of Variance results revealed that transect distance from the landfall location of Hurricane Ike was the only independent variable that could not predict or explain storm surge deposit thickness; which is very likely due to all four transects being in the right-front quadrant of landfalling Hurricane Ike. The findings of this study provide improved understanding of the spatial relationship between storm surge sedimentation and storm surge heights, valuable knowledge about the sedimentary response of coastal marshes subject to storm surge deposition, and useful guidance to public policy aimed at combating the effects of sea-level rise on coastal marshes along the northern Gulf of Mexico coastline.</p><p> </p>

Spatial Variation of Silt and Clay Sediment Deposit in Bhaktapur City

3D geological subsurface model of the Bhaktapur City is prepared using RockWork2016, which is based on 3-D Geo-scientific information system (3-D GSIS). The main aim of this study is to interpret the geological conditions of Bhaktapur city, providing subsurface geological database and its relevance to 2015 Gorkha earthquake damages. For this, the borehole data are collected from different sources and digitized in the RockWork2016 program for the generation of the 3-D attributed subsurface model. For the stratigraphy divisions of the soil, the unified soil classification system is used. From the interpretation of the developed attributed model, it is found that the central part or the core area of the Bhaktapur city has a deeper depth of the soft sediment-silt and clay rather than other surrounding parts of the city. This indicates the possibility of local soil amplification in the central part of the study area. The spatial variation of the subsurface sediment deposit is then co-relate with damage scenario caused by 2015 Gorkha earthquake.