Assessment of Climatic and Anthropogenic Controls on Bridge Deck Drainage and Sediment Removal

Bridge deck drainage is essential to prevent hydroplaning and maintain safety along major roadways. With projected changes in climate, current designs may not be sufficient and a better understanding of the primary controls (climate, bridge deck, and inlet design) on the hydraulic efficiency and sediment removal of drainage systems is needed to maintain public safety. To evaluate the controls on hydraulic drainage efficiency, 576 controlled laboratory experiments were conducted testing grate type (rectangular bar vs. curved vane) and downspout configuration (square vs. circular and 20 cm vs. 25 cm) across a range of flow rates, cross slopes, and longitudinal slopes. An additional 144 sediment erosion experiments were performed to identify controls on the removal of sediment. Hydraulic testing indicated that inflow driven by climate is a primary control on drainage efficiency and spread of water on a roadway. For anthropogenic controls, downspout opening size was found to be the primary control followed by longitudinal slope. Sediment removal results indicated that inflow regime and grate type were the primary controls on the sediment removal rate. Given that inflow, driven by climate, is a control on both hydraulic and sediment removal performance, hydraulic engineers should consider forecasted changes in rainfall intensity in their present-day drainage designs. We provide design guidance and discussion for developing a proactive approach to hydraulic infrastructure in the face of future climate uncertainty.

Investigation of the Sediment Removal Frequency for Wet-Detention Stormwater Management Ponds

The purpose of this study was to develop methodologies for determining the appropriate sediment removal frequency of wet-detention stormwater management facilities. Using data from a wet pond in the Town of Richmond Hill, a sediment accumulation model was developed using the US EPA’s Stormwater Management Model (Version 5). Two different methodologies were then developed and applied to the facility. The first methodology is a real-time tool that provides the required time for sediment removal for a single cleanout cycle. The second methodology is analysis tool that relates cleanout frequency, annual cost and violations over a 50-year planning period. The results showed that the appropriate sediment removal frequency for the pond was approximately 16 to 17 years, and the annual cost of sediment removal ranged from $2,150 to $2,372, depending on the methodology used. It is recommended that these methodologies be considered for the planning and operation phases of stormwater ponds.

Investigation of the Sediment Removal Frequency for Wet-Detention Stormwater Management Ponds

The purpose of this study was to develop methodologies for determining the appropriate sediment removal frequency of wet-detention stormwater management facilities. Using data from a wet pond in the Town of Richmond Hill, a sediment accumulation model was developed using the US EPA’s Stormwater Management Model (Version 5). Two different methodologies were then developed and applied to the facility. The first methodology is a real-time tool that provides the required time for sediment removal for a single cleanout cycle. The second methodology is analysis tool that relates cleanout frequency, annual cost and violations over a 50-year planning period. The results showed that the appropriate sediment removal frequency for the pond was approximately 16 to 17 years, and the annual cost of sediment removal ranged from $2,150 to $2,372, depending on the methodology used. It is recommended that these methodologies be considered for the planning and operation phases of stormwater ponds.

Anomalous Reduction of the Total Suspended Matter During the COVID-19 Lockdown in the Hooghly Estuarine System

The impact of the coronavirus disease 2019 (COVID-19) lockdown in the Hooghly estuarine region, India is assessed using the total suspended matter (TSM) concentration. The estimation of TSM is performed using Landsat-8/operational land imager (OLI), and an intercomparison of TSM load during the pre-lockdown and lockdown periods is done. It is observed that during the lockdown period, TSM reduced by 30–50%. This is a significant observation considering the ecological balance of the region and the fact that it is home to the largest mangroves in the world. This change in suspended matter presumably reflects the influence of reduction in anthropogenic activities owing to the COVID-19 lockdowns, such as industries, closure of shipping activities (through less dredging), and brick kilns (through less sediment removal), which are generally the primary contributors in this region. Even though these observed changes are representative of the positive influence of the COVID-19 lockdown, its implications in estuarine biogeochemistry still remain poorly quantified. The decrease in TSM content may increase light penetration, thereby increasing the primary productivity. In addition, low sediment load reaching the Bay of Bengal could influence the carbon export due to reduction in ballasting effect as reported from this region. In summary, the influence of the COVID-19 lockdown on the biogeochemistry of the aquatic ecosystem appears rather complex than thought earlier and may vary regionally based on local hydrodynamics. The analysis elucidates the complex interplay of regional lockdown and its implication in modulation of local biogeochemistry. However, the relative importance of each process in the Hooghly estuary remains to be fully evaluated.