January 25, 2022

« All News

Rich Wildman, Austin Orr, and Joanna Lewis Presented at the 12th Urban Drainage Modeling Conference

Rich Wildman, Ph.D., P.E., Austin Orr, P.E., and Joanna Lewis, E.I.T. (Oregon) presented at the 12th Annual Urban Drainage Modeling (UDM) Conference at the Southern California Coastal Water Research Project research institute in Costa Mesa, California on January 10–12, 2022.

Rich Wildman is a Project Engineer based in Oregon who focuses on stormwater quality, watershed management, and surface water quality problems. Rich develops numerical models, analyzes data, develops stormwater treatment alternatives to help clients meet their regulatory obligations proactively.

Austin Orr is a Project Engineer with consulting experience in urban stormwater management, hydrologic and sediment transport modeling, best management practice (BMP) sizing and performance evaluation, and geospatial analysis. He specializes in data analysis and visualization, software development, and workflow automation.

Jo Lewis is a Senior Staff Professional based in Oregon who contributes to projects ranging from BMP design to analysis of stormwater quality to watershed master planning.

The UDM Conference seeks to create a forum for deep discussion and exchange of ideas amongst technical experts, including engineers, scientists, professionals, and academics. The UDM Conference brings focus to the data and models needed to develop a better understanding and advance the management of the urban drainage system (e.g., water quality and quantity, urban flooding and modelling, urban flood forecasting and risk analysis, modeling tools, data).

Geosyntec Participation

The South Orange County, California Flow Ecology Study: Part 1, Watershed Hydrology
Presenters: Rich Wildman
Date/Time: January 10, 2022 | 3:30–5:00 p.m. PST

The Public Works department of Orange County, California, on behalf of a group of municipal stormwater permittees in the southern half of the county, is conducting a "Flow Ecology Special Study" for six watersheds in the South OC Watershed Management Area (WMA). Its goals are the quantification of unnatural flows and development of relationships between levels of flow alteration and in-stream beneficial uses (or ecological condition). This will inform prioritization and design of flow management and stream rehabilitation projects. The study aims to develop tools and datasets to support future projects, including (1) recovery of stream ecosystems from negative impacts of urbanization and (2) increased resilience of ecological communities during a drier future. This study was divided into two parts: watershed hydrology and flow ecology approaches for flow management prioritization. This presentation will focus on watershed hydrology modeling, and a companion, "Part 2" presentation will focus on the flow ecology components of the study.

Aliso Creek Smart Watershed Network: A High-Resolution Data Acquisition and Analysis Platform to Support Urban Runoff Management and Water Recovery
Presenters: Austin Orr
Date/Time: January 11, 2022 | 4:15–5:45 p.m. PST

Dry weather irrigation runoff from urban areas has been identified as a significant source of water quality impairment in the Aliso Creek Watershed (SOC WMA, 2018). Additionally, there is interest in harvesting dry and wet weather runoff to augment non-potable water supplies. However, urban runoff needs to be better characterized in terms of quantity and quality at an outfall level to support decision making. The large scale of the watershed (35 sq-miles) and complexity of the drainage network (more than 80 storm drain outfalls) necessitated an innovative approach to improve data availability and support efficient data analysis while controlling costs.

The Smart Watershed Network was developed through funding from the Metropolitan Water District of Southern California Future Supply Action Planning program. The aim of the project is to (1) develop a flow and conductivity monitoring network within stream channels and storm drains in the Aliso Creek Watershed, (2) pilot a system to transmit these data over Moulton Niguel Water District's (MNWD) Advanced Metering Infrastructure (AMI) network (currently used for water metering), and (3) develop a new open-source cloud-based data management, integration, and analytics space to provide comprehensive watershed information and scenario results to support planning and decision making at multiple scales.

This presentation will provide an overview of how this system was developed, with a specific focus on the open-source data management, analytics, and scenario modeling features that are being used to evaluate the sustainable use of urban runoff and stormwater as a potential water supply within the Aliso Creek Watershed.

Developing a Surface Water – Groundwater Model for Green Stormwater Infrastructure to Estimate Water Supply Benefits
Presenter: Scott Struck
Date/Time: January 12, 2022 | 9:45–11:15 a.m. PST

The Los Angeles Basin Study (Basin Study) identified improvements to Los Angeles (L.A.) County's stormwater infrastructure as critical to the resilience of regional water supply providing improved Integrated Water Cycle Management, especially when considering the potential effects of climate change (Simes et al., 2016). Managing LA's future water allocation is paramount and would be a paradigm shift in traditional water supply management practices from current approaches. Decentralized stormwater infiltration using stormwater control measures (SCMs), which the Basin Study categorized as Local Stormwater Capture using green stormwater infrastructure SCMs (GSI; also termed sustainable urban drainage [SUDS] and water-sensitive urban design [WSUDs] were determined to be key components of the Basin Study for future water supply. Regional modelling of widespread infiltration SCMs found that they could increase local water supplies by over 183,000 AFY in the middle climate scenario of those evaluated. However, the Basin Study assumed that all water infiltrated through decentralized infiltration systems would reach usable aquifers and benefit water supply.

While models use simple (constant hydraulic conductivity value) to complex (Green Ampt) or empirically based approaches (SCS model) to represent soil water infiltration processes, the basis for many of these models was not derived for water supply benefits. Controlling factors such as rate and duration of water application, inundation depth (head), soil physical properties, slope, and vegetation to predict downward percolation that can recharge groundwater supplies is required. To develop a model that estimates groundwater recharge based on an empirical determination of infiltrating stormwater practices such as bioswales, bioretention cells, infiltration galleries, infiltration basins, and drywells, further information must be collected. This study sought to document infiltration from various types of infiltration SCMs to:

  • Determine the sensitive drainage and soil physical properties that indicate deep percolation,
  • Use novel methods (ERT) to quantify and visualize water infiltration dynamics over time,
  • Develop a 2-D and 3-D model platform that represents the physical processes of surface water-groundwater transfer, and
  • Demonstrate model parameterization, calibration, and uncertainty for future model application in the Southern California region.

After considering several modelling platforms for this effort, the U.S. Environmental Protection Agency's Green Infrastructure Flexible Model (GIFMod) was selected (US EPA, 2021). This conceptual model is a computer program that can be used to evaluate the performance of urban stormwater and agricultural GSI practices to predict their hydraulic and water quality performance under given weather scenarios. GIFMod can also be used for interpreting field and lab data and has deterministic and probabilistic capabilities (Alakhani et al., 2020).

Development of an Online Performance Calculation Tool for Bioretention Projects in Seattle, WA, USA
Presenters: Joanna Lewis
Date/Time: January 12, 2022 | 9:45–11:15 a.m. PST

The City of Seattle (City) manages stormwater through a combined sewer system and a municipal separate storm sewer system (MS4), both of which are permitted under the National Pollutant Discharge Elimination System (NPDES) by the Washington State Department of Ecology (Ecology), the state regulatory agency. While the storm sewer system serves approximately two-thirds of the city, discharging approximately 13 billion gallons of stormwater to receiving waters in and around the city during an average year, the City has historically contributed limited resources toward addressing water quality impacts of discharges from the City's MS4, focusing instead on CSO discharges. Ecology determined that stormwater runoff was a main pathway through which toxic pollutants enter Puget Sound (Ecology, 2011) and may contribute more than 50 times as much flow and 30 times as much solids loading to the Lower Duwamish Waterway, a major Seattle receiving water, compared to CSO discharges (Ecology, 2013).

To address stormwater-related impacts to receiving waters, the City developed an "Integrated Plan" (City of Seattle, 2015). This Plan allows the City to implement stormwater control projects that will significantly benefit water quality in receiving water bodies, while deferring lower-benefit CSO projects. The Integrated Plan is composed of three major projects. One project—Natural Drainage Systems (NDS) Partnering— includes the installation of bioretention stormwater management systems along City roadways. The bioretention systems manage flow and provide water quality treatment of urban runoff, thereby decreasing flow volume and pollutant loads to City receiving waters.

For regulatory acceptance of the City's Integrated Plan approach, the City agreed to demonstrate that the stormwater projects provide water quality benefits beyond those that would be achieved by the CSO projects alone. To assist in demonstrating success, post-construction monitoring is required from several NDS Partnering projects, the data from which can be used to estimate performance of other similarly implemented facilities and track progress toward achieving goals defined and accepted by Ecology.

This paper discusses the development of a simplistic tool to track, estimate performance, and allow scenario analyses to determine the number of stormwater investments through implementation of bioretention systems necessary to meet regulatory load reduction and volumetric goals.

More Information

About the event: 12th Urban Drainage Modeling Conference
For consultation regarding urban drainage modeling, contact Scott Struck at This email address is being protected from spambots. You need JavaScript enabled to view it.
Learn more about Scott: Scott Struck | Geosyntec Profile
Learn more about Rich: Rich Wildman | LinkedIn
Learn more about Austin: Austin Orr | LinkedIn
Learn more about Joanna: Joanna Lewis | LinkedIn