**Abstract Text**
The recently-launched NASA Surface Water and Ocean Topography (SWOT) Mission will provide first-of-its-kind satellite swath altimetry by simultaneously measuring surface-water elevations and water extent. SWOT will provide these unique data for inland water bodies at high vertical (<10 cm) and spatial resolution (3-40m) over large spatial scales; every hour, SWOT observes more than half a percent of Earth’s area. For many large global rivers, nearly the entire river systems will be observed over the course of several minutes with repeat times of approximately once every ten days in mid-latitudes and up to eight times per 21-days in high latitudes. SWOT will greatly advance global observations of lakes and large rivers, particularly in locations lacking gage data. For regions with gage data, there are additional benefits including improving hydrologic and hydraulic modeling, refining water-balances of lakes and watersheds, estimating inland bathymetry, and assessing habitat conditions for fisheries. Because of the novel satellite instrument design and its first-of-its-kind observations, the calibration and validation (cal/val) of the data will be particularly important. CIRES is co‑leading cal/val of SWOT inland water measurements and data products. In this talk, an overview of SWOT will be presented, as well as cal/val plans for the satellite and observations, including plans for the western CONUS.



The NASA Surface Water and Ocean Topography (SWOT) Mission: Advancing Global Inland Hydrology (Room 322, June 26th, 3:30pm-5:00pm)

**Abstract Text**
Infrared quantitative image velocimetry (IR-QIV) is a large scale surface velocimetry method that uses infrared imagery to calculate the mean and instantaneous  velocity at high resolution in space and time, over large spatial areas (Schweitzer & Cowen, WRR 2021). IR-QIV can operate continuously for extended periods (days, weeks, etc.) without requiring artificial illumination or particle seeding of the flow. The high resolution, continuous, measurement capabilities of IR-QIV make it particularly well suited to applications such as fishery management studies, where metrics of the flow must be resolved and correlated with fish behavior.

We present results from using IR-QIV as part of a large fishery management project in California, USA. The junction of the Sacramento River and Georgiana Slough is a tidally forced, hydrodynamically complex river junction, at which navigational choices of migrating salmonids and other fish have significant impact on their survival rates. A bio-acoustic fish fence (BAFF) was installed on site by the California Department of Water Resources (DWR) to divert fish towards the routes with higher survival probabilities. IR-QIV measurements were conducted to inform management practices, and results are presented here, including comparison to ADCP velocity measurements conducted on site by the US Geological Survey (USGS).



Infrared Quantitative Image Velocimetry (IR-QIV) Measurements at a Tidally-Forced River Junction (Room 312, Tuesday June 27th, 2:00pm-3:30pm)

**Abstract Text**
Detailed hydrological floodplain studies and modeling of flows in the vicinity of hydraulic structures require precise definition of channel topographies. In recent years, LiDAR datasets became commonly available nationwide in the United States thanks to the USGS 3DEP program. However, bathymetric surveys are usually needed for hydraulic studies involving deeper flows since conventional LiDAR measurements do not penetrate water. Additionally, often the LiDAR data sets collected prior to flood events do not represent the existing terrain. In this paper, a hybrid terrain measurement methodology using LiDAR, drone photogrammetry, sonar transducer, real-time kinematic GPS, and total stations to perform ground and underwater terrain mapping is presented. This methodology was successfully used conducting 1-, 2-, and 3-Dimensional hydraulic modeling in numerous state-wide bridge scour studies in Colorado.  The methodology takes advantage of various measurement techniques in assembling accurate topography in a time-efficient and practical manner. The drone photography coupled with  proper ground control points is used in providing detailed and precise survey results near the points of interest to supplement LiDAR data, if available. For bathymetric mapping, a floating continuous data acquisition system  is developed attached to an ultrasonic sonar transducer. A survey prism attached to the floating device allows the location of the equipment can be tracked very accurately with a robotic total station while being towed by a motorized vessel. The hybrid terrain generated using various layers of data sets can then be used for detailed hydraulic simulations such as 2-dimension or 3-dimension hydraulic modeling. Additional data sets using virtual reality photogrammetry are also used to supplement the hybrid terrain for design visualization and various roughness and loss coefficient selection.



Hybrid Channel Geometry Measurements for Hydraulic Studies (Room 322, Monday June 26th, 10:30am-12:00pm)

**Abstract Text**
There has been enormous utilizations of Laser Induced Fluorescence (LIF) systems in the empirical studies on hydraulics and mixing characteristics in water chambers confined by transparent walls. Recently, the technology has evolved to four-dimensional (Time-resolved Volumetric). However, as other experimental devices are, the commercial LIF systems are exorbitant for simple, academic studies. For a scaled flow channel (the maximum channel length at around 20 inches), a planar laser sheet of a 405 nm wavelength blue laser pointer pen through a concave water prism lens was strong enough for the fluorescent solution made from yellow highlighter ink. The dispersion of the fluorescent solution released through a syringe in the water flow has been recorded using a DSLR camera without auto-focusing and auto-brightness-adjustment features. The recorded video clips were converted to the image sequence at a certain fps. The original colorful image has been converted to a mono spectrum that let us obtain a concentration distribution. Due to the random gradation of brightness in the laser sheet affected by various environmental sources, the raw concentration levels at different locations in the laser sheet were different; nevertheless, the data collected at each probe and at different runs could be compared after secondary data manipulations, such as normalization. The fluorescent dye’s residence time distributions obtained from the present study were verified with the data from the previous study for the same water channel configurations using a commercial high-speed 3D LIF system indicating that the affordable system used for the present study is accurate enough.



The accuracy of an affordable planar laser induced fluorescence system for the hydraulic mixing performance in a scaled serpentine chamber (Room 312, Monday, June 26, 10:30 am-12:00 pm)

**Abstract Text**
Sediment transport is important for several estuarine functions. The morphology determines both the tidal penetration in the estuary, port accessibility and ecosystem services. Suspended sediment influences the light penetration in the water column and is therefore crucial for ecology. The residual sediment transport is crucial for the future evolution of the estuary. Therefore a sediment balance is calculated for the Scheldt-estuary. A distinction was made between the transport of non-cohesive (sand) and cohesive (mud) particles.
The sediment balance is calculated starting from topo-bathymetric surveys from 2 different moments. The differences in volume are explained by sediment transport at both the up-estuarine and down-estuary boundary, but also by human interventions (e.g. dredging, disposal, extractions). For the Scheldt-estuary, information is available for several decades, although all necessary data could only be collected since 2001. Over the last 20 years, 3 different time periods are investigated (2001-2011, 2011-2016 and 2016-2019), related to the availability of full-estuarine topo-bathymetric datasets.
The distinction between sand and mud was made based on the sand-mud-percentage for several 100’s of bottom samples. Where some data were available as volumes, while others were available as masses, it was chosen to convert the volumes to masses, using both porosity and sediment density. With the data, the sand and mud transport was calculated for segments of 5 to 10 km long. The sand transport shows an up-estuarine transport over the entire estuary. The mud transport has a different pattern, with a down-estuarine transport over most of the estuary. Only at the most downstream location, mud transport is up-estuarine. This difference can be explained by the different behaviour of the sediments in relation to flow velocity: for mud transport the classic advection-diffusion equation is valid (relation to velocity to the power 1), while for sand transport typical transport formulas are used, eg. Engelund-Hansen formula (relation to velocity to the power 3 to 5).
Comparing different periods shows similar residual transport directions, although the magnitude varies between different periods. A possible explanation is the temporal variation of fresh water discharge in the Scheldt-estuary. This will certainly have an effect on the mud transport, but seems to have an effect on the sand transport as well. This analysis has shown the temporal and spatial variation in sand and mud transport and is an instrument that can be used in future estuarine management.



The residual sand and mud transport in the Scheldt-estuary, derived from the sediment balance (Room 322, Wednesday June 28th, 8:30am-10:00am)

**Abstract Text**
The proliferation of simple, low-cost computing and instrumentation platforms is leading to incredible improvements in measurement capabilities. There are many benefits of do-it-yourself, or DIY, instrumentation, chiefly among them are the relatively low cost to acquire materials and fabricate your own sensor. The DIY platform does, however, come with some trade-offs. For one, the low-cost components are not always robust, which raises questions about their long-term reliability and measurement repeatability. Temple et al. (2020), and more recently Virden et al. (2022), demonstrate the measurement accuracy of a DIY pressure gauge for measuring water levels and waves in the lab and/or field. While initially intended for relatively short deployments of days to weeks, the MEMS pressure sensor manufacturer’s datasheet states that the user should dry the gel-filled membrane regularly to prevent measurement drift. The datasheet suggests drying as frequently as once per day. Though researchers have been using these gauges in the field for nearly three years, we currently do not know the magnitude of the drift, if it is repeatable, and if it is reproducible from gauge to gauge. This  presentation will demonstrate the results of controlled (laboratory) testing of these DIY pressure gauges and provide recommendations for multi-day deployments where measurement drift may be a concern.



Reliability of a Low-Cost DIY Pressure Gauge for Measuring Water Levels and Waves (Room 322, Tuesday June 27th, 8:30am-10:00am)

**Abstract Text**
The present study presents a five-parametric analytical model to determine the depth-averaged velocity and boundary shear stress distribution in prismatic compound channels. An analytical solution to predict depth-averaged velocity and boundary shear stress distributions in rectangular compound channels. The analytical solution to the streamwise depth-averaged momentum equation includes the effect of non-dimensional coefficient (β), secondary flow term (Г), bed friction factor (f), secondary flow coefficient (k), and dimensionless eddy viscosity (λ) is presented. Thus, the analytical expression to determine the non-dimensional coefficient is developed. Different boundary conditions at the main channel and floodplains are presented and used to determine the integration constants. For model validation, extensive laboratory experiments have been carried out on a compound channel with a ratio of the total width of the channel to flood plain ranging from 1.6 to 3. In addition, the model is also validated with experimental data from Birmingham University. The analysis shows that the depth-averaged velocities are found to be sensitive to a shear stress-dependent model parameter. The performance of the present model is also compared with the earlier existing models, and the present model is found to perform better when compared to earlier models. Using the proposed model and derived expressions leads to better simulations of depth-averaged velocity in the present experiments and Birmingham University channels data. Thus, it promises to simulate the flow field and related characteristics in a better way. There may be a need for further evaluation of the proposed model in more complex environments or flow conditions in compound channels, and this part is preserved for future investigations. The application of the present model can be a powerful tool for sediment analysis, river engineering, flood control structures, modelling flows in complex channels, and designing and planning water resource structures that may benefit from expanding the proposed model. More investigation on this application is recommended and forwarded. It may be developed with more complex flow conditions, and the extension of the proposed model can be the subject of further investigations.



Modelling Depth averaged velocity and Boundary Shear Stress distributions in compound channels with different floodplain widths (Room 312, Wednesday June 28th, 10:30am-12:00pm)

**Abstract Text**
The climate change caused by the excessive emission of CO2 has caused an increase in the global warming that has motivated the countries around the globe to set the global goal of net zero carbon dioxide emission. One way of mitigating climate change is to adopt low-carbon and energy-efficient technologies. Another way of reducing the climate change is to use the negative emission technologies in which carbon dioxide is stored in deep geological reservoirs for long time. In order to inject CO2 into the deep geological reservoirs, it is necessary to use high values of injection pressure. Injecting CO2 at high injection pressure will cause an increase in the reservoir’s pressure. The faults that already exists in the reservoir and caprock are normally very sensitive to the pressure buildup and can be activated with excessive increase in the reservoir’s pressure. The stored CO2 in the reservoir will leak to the overburden layers after the fault’s activation in the reservoir and caprock. The CO2 leaked to the overburden layers will eventually contaminate the underground water sources and will finally leak to the earth’s atmosphere. In this paper, the coupled reservoir-geomechanical analysis and CO2leakage modeling have been performed during the injection of CO2into the Hanifa reservoir. The location of the Hanifa reservoir is very feasible for CO2 injection because it is capped by the impermeable geological layers of Hith Anhydrite and Rus Anhydrite that will prevent the leakage of the stored CO2 into the Umm Er Radhuma potable water layer and to the earth’s atmosphere. The structural deformation of the reservoir is modeled in this study that results in the vertical deformation of the ground surface. The coupled stability analysis is performed during CO2injection; by taking into account both the variations in the reservoir’s pore-pressure and stresses. The CO2 leakage modeling has been performed by considering a fault passing from the reservoir and caprock. Based on the stability analysis of the reservoir, safe CO2 injection parameters have been evaluated for the Hanifa reservoir that will prevent the leakage of the stored CO2 from the reservoir.
Keywords: Reservoir-Geomechanical Analysis, CO2Leakage, Climate Change Mitigation, Global Warming, Ground Vertical Displacement, CO2 Geological Storage



Coupled Reservoir-Geomechanical Analysis and CO2 Leakage Modeling during CO2 Injection into the Hanifa Reservoir: A Study Focused on Climate Change Mitigation (Room 312, Tuesday June 27th, 8:30am-10:00am)

**Abstract Text**
Sediment mining is extracting sand and gravel from river beds and flood plains to meet various essential construction demands. If not properly managed, sediment mining is one of the most common destructive operations to hydraulic structures and river ecosystems. The majority of researchers largely focused on the physical aspects of sediment mining. A few studies on quantitative sediment mining aspects and their morphological change are documented in the literature. This study focused on the experimental work performed on a full-span trapezoidal sediment mining pit composed of cohesionless sediment in an open channel flow to determine the influence of sediment mining on flow field patterns and morphological characteristics. The experiments in this study were conducted in a tilting flume of 12.5 m in length, 0.46 m in width, and 0.7 m in depth for gathering data on flow regimes and morphological variations near the pit under various flow conditions and pit dimensions. A high flow depth in the sediment mining pit causes velocity to decrease, leading to bed load deposition in the pit. As the flow approaches the pit center, 3D velocity components measured with an Acoustic Doppler Velocimeter decrease and eventually turn negative, resulting in reverse flow. The velocity fields and bed evolutions at the upstream, pit center, and downstream nicks were investigated, and it was observed that the lateral and vertical velocities increased significantly. The findings of this study can help authorities and experts in the effective maintenance and supervision of river ecosystem balance by supplying cost-effective sediment resources.



Experimental Study of Hydromorphological Features Near a Sediment Mining Pit Constructed in Open Channel Flow (Room 312, Wednesday June 28th, 10:30am-12:00pm)

Plants are a key part of LID/GSI bioretention systems. They provide functional value and multiple environmental, social, and community benefits. LID systems are touted as a visual amenity to communities through lush plantings and immersive landscapes. Achieving and maintaining LID as a community amenity takes work and practitioners have found it is more difficult than initially thought to bring the lush landscape to life. Plants need water and good soil conditions, competition with weeds needs to be controlled, and maintenance crews need to know what they are maintaining.
This workshop will give practical tips on how to create and maintain a planted landscape to survive and thrive. What are the best plant selections, what establishment regime is needed, and how little maintenance can be done? This interactive workshop will bring together landscape professionals and municipal program managers to give you the time tested and latest techniques to create bioretention landscapes to survive and thrive. Bring your planting challenges and share with the group while the experts provide strategies and solutions. Practical solutions will be discussed that you can incorporate into your planting designs and program.

Planting Strategies to Survive and Thrive: Keeping the Bio in Bioretention

Presentation Outline

Introduction and site suitability evaluation methods and tool
Municipal flood reduction examples and pollutant reduction performance
Hydrologic design overview
Structural design method developed from full-scale PICP load testing
Construction do’s and don’ts
Handling slopes and utilities
Maintenance evaluation methods and recent developments in cleaning equipment

Permeable Interlocking Concrete Pavement

The i-DST is a planning-level stormwater decision support tool that helps practitioners select the most appropriate suites of green, grey, and/or hybrid infrastructure. The tool is modular and composed of site-scale and sewer-shed scale hydrologic modeling, life cycle cost and life cycle assessment, and a co-benefit analysis. The sewer-shed hydrologic model uses an updated version of the EPA’s SUSTAIN to optimize the types and numbers of varying stormwater infrastructure in order to determine the best-fit scenarios for decision makers. Updates to SUSTAIN for this tool include a new user friendly GUI (Qt) to read, write, and run SUSTAIN input files, an improved list of evaluation factors to optimize on, greyer underground detention/infiltration infrastructure, and a life cycle cost estimation tool that is integrated with the SUSTAIN optimization engine. The co-benefit analysis is utilized to evaluate the benefits and tradeoffs between greener and greyer stormwater infrastructure. The purpose of this workshop is to beta test the different modules of this tool and receive feedback from participants. The team running the workshop will provide a test case scenario, but participants are encouraged to bring their own data (i.e. modeled or observed flow/water quality times series, stormwater infrastructure design parameters) to be input into the tool.

Integrated Decision Support (I-DST) Beta Testing for Stormwater Practitioners

The Bioinfiltration Traffic Island (BTI) is a bioinfiltration rain garden that was retrofitted off an existing traffic island in 2001. Having been monitored since 2003, the BTI has quantitative hydrological data collected for the past 15 years, making it a very valuable dataset for an in-depth analysis of the performance of the site.

The initial analysis comprises of a high-resolution analysis of rainfall event frequency along with resulting performance at the bioinfiltration rain garden. All rainfall events within the 15 years of collected data was discretized in to 2.5 mm, 2-hour bins. The binned rain events were then analyzed using a mass balance approach to understand how the different hydrological elements contribute to the ability of the site to treat incoming stormwater runoff. Each component of the hydrological cycle within the BTI will be studied in detail and over different types of rain events. The second part of the analysis focuses on assessing the intensities of each of the recorded storms to understand its influence on the performance of the rain garden.

Preliminary results show that between 2003 and 2018, there were 1202 recorded events, and 82% of them were less than 25 mm. Approximately 16% of all observed events resulted in substantial overflow. The overall analysis provides lessons into system components and aims to understand the interaction of the different hydrological elements within the rain garden. The objective is to use the findings in designing Green Infrastructure systems that can be optimized in their ability to manage and treat incoming stormwater.

Access the Conference Proceedings Paper on ASCE Library 

Analyzing the performance of a rain garden over 15 years

Closing Plenary- Future Opportunities of the Value-Add of LID

Approximately 60% of all streams in the conterminous U.S. are ephemeral or intermittent. In the southwestern U.S., they make up more than 80% of all water courses. While dry during most of the year, ephemeral streams (also called arroyos) episodically convey runoff and sediment following intense summer storms. Arroyos provide a wide range of ecological functions such as habitat and hydrologic connectivity. Perhaps less notably, they also furnish ecosystem goods and services important for human well-being: groundwater recharge, water quality benefits and recreation, to name just a few examples. Despite their vast spatial extent, dryland watersheds and the arroyo systems they support have received less attention compared to their perennial counterparts. Under natural conditions, arroyos are in a state of dynamic equilibrium between sediment supply and transport. This equilibrium is disrupted by urbanization. In urban areas, impervious cover causes increased surface runoff. This, in turn, increases the magnitude and frequency of runoff events. At the same time, imperviousness prevents erosion, and runoff from municipal areas carries little sediment. Increased discharge and decreased sediment supply lead to channel degradation. In the past, runoff from urbanizing areas was often treated as a nuisance, and arroyos were seen as having one sole purpose: to get rid of stormwater as fast and efficiently as possible. This short-sighted view of ephemeral systems overlooks the multitude of ecosystem services they provide. Channel degradation has a profound negative impact on the welfare of dryland watersheds and the people that inhabit them. This study examines one arroyo in central New Mexico where urbanization-induced stressors have led to substantial degradation. Engineered elements designed to increase channel stability have had the opposite effect and exacerbate the problem. Important ecosystem services provided by the stream are identified, and possible restoration strategies are discussed. This example demonstrates that low impact development in a semi-arid setting requires rethinking of traditional engineering approaches.

Access the Conference Proceedings Paper on ASCE Library 

Stressors, Ecosystem Services, and Restoration Strategies for a Central New Mexico Arroyo

Urban street trees are a key part of public green infrastructure in many cities. Leaf litter on streets is a critical biogenic source of phosphorus (P) in urban stormwater runoff. Stormwater extracts P from leaf litter and transports it directly to a receiving waterbody through storm sewer network. The goal of this study is to understand P leaching dynamics of two prevalent tree species (Norway Maple and Green Ash) and its impact on end-of-pipe P concentration (Pconc) and load (Pload) in stormwater runoff. Five urban residential basins in Wisconsin were monitored by the U.S. Geological Survey to evaluate the water-quality benefits of municipal leaf collection during Fall 2017 and 2018. Laboratory experiments showed that total P release from Norway maple (2.10 mg/g) was greater than from Green Ash (1.60 mg/g). Within the same species, increased fragmentation of leaves led to more rapid initial P release, but not greater total P release over a 48-hour period. Increased decomposition of leaves led to a notable decrease in total P release. Incubation temperature and volume of water in contact with leaves may not be critical factors affecting P leaching dynamics. Multiple linear regression analyses were used to relate Pconc and Pload to street leaf litter characteristics and storm event hydrologic variables. The key explanatory parameters that affect Pconc were street leaf litter mass (Mleaf) and antecedent dry days, while Mleaf and runoff volum explained Pload. Results from our study can be used to evaluate P reduction credits for leaf collection in regulated cities.

Impact of Street Leaf Litter on Phosphorus in Urban Stormwater Runoff

Previous research regarding street trees designed for stormwater management have demonstrated the ability to remove pollutants; however, bypass does occur during intense storm events. Research by North Carolina State University (NCSU) indicates a treatment train consisting of permeable pavement parking stalls and a street tree system located underneath the adjacent sidewalk can reduce bypass. However, this combination of stormwater control measures (SCMs) can be expensive and difficult to maintain. As a result, NCSU, the North Carolina Clean Water Management Trust Fund (CWMTF), and the City of Burlington have collaborated to design, construct, and monitor the state’s first permeable gutter and street tree treatment train. Inflow is estimated using an EPA Storm Water Management Model (SWMM) while water quality data is collected from a nearby catch basin using a paired watershed experimental design. Water quality samples are also collected from the gutter and street tree’s underdrain systems. Effluent hydrology and bypass are monitored at a catch basin located immediately downstream of the treatment train. Results from this study will include the system’s pollutant removal and hydrologic efficiencies as well as design and maintenance recommendations.

Evaluating a Permeable Gutter and Street Tree Treatment Train for Stormwater Management

As part of the New York City Department of Environmental Protection (DEP) Green Infrastructure Program, the Bureau of Environmental Planning and Analysis (BEPA) implemented a pilot project in Rego Park, Queens to install and test the performance of precast porous concrete panels in a typical NYC street. BEPA initiated this pilot project for a 27-acre contributing drainage area to achieve the green infrastructure related milestone requirements of DEP’s Combined Sewer Overflow (CSO) Consent Order. This pilot project also fulfills the requirements of Local Law 80 of 2013, which requires a study be conducted within streets and sidewalks to gather information on the design, construction, maintenance and performance of various porous paving materials. Construction of 6,270 linear feet of porous concrete panels was completed in January 2019. The panels extend from the curb line into the street at a width of four feet, bound by a flush curb on the street side. HDR oversaw field and geotechnical investigations, provided a preliminary design report, final construction documents, design services during construction, pre- and post-construction performance monitoring and maintenance studies to carry out the first large-scale pilot project of porous concrete in the City’s right-of-way. Siting and design were coordinated with NYCDOT, NYCDPR, and local utility agencies to accommodate varying field conditions and geotechnical criteria, adhere to design criteria, and address conflicts. This allowed us to implement stormwater retention in an area that prohibited other types of green infrastructure. Additionally, design services during construction were vitally important to address any challenges that arose during implementation. Performance monitoring will be conducted during 12 month pre- and post-construction periods. In addition to flow measurements, performance monitoring is comprised of visual observation, traffic analyses and controlled testing. Design, construction and post-construction monitoring phases have concluded. Lessons learned during design and construction, as well as data collection procedures and observations from monitoring will be shared during the presentation.

Porous Concrete Panels in a NYC Street: From Design Through Post-Construction Monitoring

Building Equitable Stormwater Infrastructure - A Panel Discussion

In early 2017, the University of California Pavement Research Center and the National Center for Sustainable Transportation, working with the Interlocking Concrete Pavement Institute, identified gaps in knowledge and other barriers to wider implementation that were perceived to be holding back the full potential for deployment of pavements that can simultaneously solve transportation, stormwater quality, and flood control problems. Further discussions were held with the National Ready Mixed Concrete Association, the National Asphalt Pavement Association, and the Tongji University Sponge City Project in Shanghai, China. A workshop was organized in November 2017 to identify knowledge, information, and communication barriers to adoption of permeable pavement of all types, and creation of a road map to help overcome them. The workshop brought together a diverse group of stakeholders from the planning, stormwater quality, flood control, and pavement spheres to listen to presentations, exchange and discuss unanswered questions identified by the group. The group also provided a framework for a road map to fill the gaps in knowledge, processes, and guidance. This presentation summarizes the workshop deliverables. These include the following map routes with detailed deliverables and funding: Route 1. Infrastructure management organizations that consider the full functionality of permeable pavements Route 2. Planning guidance that considers the multi-functionality of permeable pavements Route 3. Accurate life cycle cost analysis and environmental life cycle assessment tools Route 4. Reduction of target pollutants to meet water quality requirements Route 5. Reduction of urban flooding risks Route 6. Reliable pavement structural designs Route 7. Routine achievement of high-quality construction. Route 8. Maintenance and rehabilitation costs and methods Route 9. Incorporation of permeable pavements into asset management systems Route 10. Efficient and comprehensive access to the best information

A Road Map for Permeable Pavements

In early 2017, DC Water, in collaboration with District agencies, developed a standard design process for permeable alleyways using GIS and standard construction details. Field tablets were used to quickly evaluate potential sites, where the efficiencies of a standardized approach would be realized. Working closely with permitting agencies, DC Water updated its design details to accommodate both a streamlined permitting process and the issuance of a blanket permit as well as creating a simplified design package for the Contractors to bid on. This process was further refined during the implementation of the Districts AlleyPalooza program.
The partnership between DC Water and DDOT provided the opportunity to expand our standardization tool box to include simplified specifications, erosion and sediment control measures, MOT, and testing protocols. DC Water realized that implementing standard designs in a diverse, highly urbanized environment also comes with challenges and risks, and needed to remain nimble to account for these challenges, not just through the design process, but also during and after construction.

The Potomac River-A and Rock Creek-A projects account for the first two of eight GI projects in the nation’s capital, part of its Long-Term Control Plan to reduce combined sewer overflows. Under DC Water’s consent decree, modified in 2016, the Authority will design and construct GI facilities to manage 1.2” of rainfall on 498 impervious acres between now and 2030.

The Potomac River-A and Rock Creek-A GI projects highlight a myriad examples of variable physical site characteristics which the standard designs had to account for, such as unknown utilities, unclear property lines, buttressing tree roots, unusual street drainage, and degraded areas adjacent to proposed GI. Site verification, basic property line analysis, 360-degree imagery were critical tools for successful siting of standard designs during the design stage. However, DC Water was realistic and understood that undertaking construction of a standardized design in the built environment would require field adjustments to accommodate the unknowns when working in the urban landscape.

During construction, the “one-size-fits-all” installation of a standard design proved to provide the construction efficiencies anticipated. Nonetheless, as green infrastructure was being constructed, performance due to site variabilities became apparent as well as the need for increased maintenance. For example, in finished alleys, the amount of sediment captured within the facility was due to the variability within the physical characteristics of the properties served by the alley. These characteristics included parking pad materials (concrete, stone, dirt), property interface with the alley (grass, landscape-wall with weep holes, bare dirt) and quantity of roof disconnections directed onto the alley. These elements are not always accounted for in developing a standard design but can cause performanc

Maximizing the Benefits of Standardized Green Infrastructure During and Post Construction

The pressure imposed by human activities is a leading cause of increased ecological risks to urban ecosystems. Low impact development (LID) has been progressively applied as a source and green solution to restore the hydrologic process of urban ecosystems and ultimately to mitigate risks. In order to identify the priority sites of LID solutions, it is essential to first understand the spatial features of ecological risks. We developed a framework for prioritizing LID sites based on an ecological risk assessment (ERA) and applied it to an environmentally sensitive catchment in Shenzhen, China. The ERA was implemented depending on a series of factors contributing to the spatial distribution of risks across the catchment, including topography, hydrology, vegetation coverage, human activities, and ecologically sensitive elements. We first employed the fuzzy analytic hierarchy process method to determine weights for these factors and then performed a multifactor-based spatial superposition analysis in the geographic information system to produce a risk map. The risk map was first validated to ensure the reliability of the ERA and then applied to establish the priority of LID solutions for the natural and built environment at the catchment scale. The map indicated that the area at extremely high risk accounts for 4.3% of the total catchment area, in which 60.4% of the area is built-up areas, mainly distributed in the area surrounded by the Dashanpo Reservoir, Chiao River, and Nanping expressway. These areas are considered priority sites for implementing LID solutions, which can restore ecosystem resilience of built-up areas by means of regulating rainfall-runoff process, reducing non-point source pollution at the source, and increasing rainwater reuse potential. It also showed that the natural environment with extremely high risk is mainly distributed around and within (21.8%) water-source reserves. LID solutions to prevent these ecologically sensitive elements from human activities should be considered on an urgent basis. The proposed framework of ERA-based LID site prioritization is conducive to develop effective LID implementation plans, which is also applicable to the sustainable urban development of other regions.

Identifying priority sites for low impact development at a catchment scale based on the assessment of ecological risks induced by human activities

Winter deicing salt application has led to water quality impairment as stormwater carries salt ions (Na+ and Cl-) through watersheds. Green infrastructure (GI) is a promising urban stormwater management practice, but its efficacy in managing salt is unknown. GI is not yet designed to treat salt, but may have potential to mitigate its loading to surface waters. Two roadside infiltration GI practices in Northern Virginia (bioretention and bioswale) were monitored year-round over 28 precipitation events to investigate the transport of salt through modern stormwater infrastructure. Stormwater runoff volumes and concentrations of salt ions entering and exiting each GI were monitored to determine reductions of salt ions. Both the bioretention and bioswale significantly reduced loads of Cl- and Na+ (76% to 82%), displaying ability to temporarily retain and infiltrate salts and delay their release to surface waters. Changes in bioretention soil chemistry revealed a small percentage of Na+ was stored long-term by ion exchange, but no long-term Cl- storage was observed. Limited soil storage along with groundwater observations suggest the majority of salt removed from stormwater by the bioretention infiltrates into groundwater. Infiltration GI can buffer surface waters from salt, but are also an avenue for groundwater salt loading.

Green Stormwater Infrastructure Buffers Surface Water from Deicing Salt Loading

Optimizing stormwater capture for urban green infrastructure is contingent on the placement and performance of inlets. It is crucial to thoroughly examine the benefits and drawbacks of each type when designing a reliable system, be they grate, curb opening, combination, or slotted drain inlet types. In ultra-urban environments, site constraints often control the selection and placement of inlets, introducing the complication that hydraulic preferences may not always be achievable. Careful optimization is needed to achieve stormwater capture goals while minimizing costs, considering maintenance efforts, and protecting public safety. Inlet and green infrastructure functionality will be discussed as a function of site factors and hydraulic factors, including through the lens of future climate and rainfall pattern variability. The presentation will provide a detailed analysis of these factors to ensure the appropriate inlet tributary to green infrastructure is installed at the optimum location, including placement at gutter sag points or upstream of sag locations (“on grade”) when future more intense rainfall patterns play a role. Implications of improperly-sized or sited inlets will be discussed, including localized ponding and idle green infrastructure systems. Hydraulic considerations that can be exacerbated by future climate hydrologic variability include debris clogging, slope, drainage area, and inlet geometry. The annual performance of green infrastructure under different rainfall intensity scenarios associated with climate uncertainty will be used to examine inlet configurations insofar as green infrastructure performance is concerned, while addressing these impacts on alleviating roadway drainage hazards.

Green infrastructure right-of-way inlet type selection: Hydraulic, hydrologic, and siting factor considerations to optimize long-term design capture goals

Presentations