Abdo, Khaled

Khaled Abdo was a speaker at the WEFTEC 2025 conference held in Chicago, IL from September 27-October 1.

Titles from this speaker

2D Storm Water Modeling: Case studies and lessons learned

Abstract

Abstract
Two-dimensional (2D) storm models are crucial for assessing current and future conditions of various storm system components. These models help identify system deficiencies and understand flooding causes. Two common methods for developing 2D stormwater models are the Catchment-Based Hydrology method, which calculates runoff at the subcatchment level, and the rain-on-mesh approach, where rainfall applies directly to the 2D mesh. Each has its own strengths and weaknesses, with the choice dependent on available data and the required detail.

This presentation discusses insights and findings from two case studies: Houston, TX's stormwater master plan using the rain-on-mesh approach, and Fayetteville, NC's watershed master plan using Catchment-Based Hydrology for secondary systems and HECRAS for primary streams and channels.

Objective
Flooding in U.S. communities, exacerbated by riverine impacts and outdated stormwater systems, can be mitigated through 2D stormwater modeling, which improves flood risk prediction and system deficiency identification. The presentation highlights lessons and challenges from case studies in Fayetteville, NC, utilizing a Catchment-Based Hydrology approach known for its lower computational requirements and reliance on precise subcatchment delineation and runoff parameters; and Houston, TX, applying a rain-on-mesh approach, which captures detailed surface flow routes but demands higher computational resources.

The presentation details the necessity of 2D stormwater modeling, the advantages and drawbacks of different methods, and critical steps in data gap analysis involving storm network connectivity, sewer data, and LiDAR data review.

Additionally, this presentation elaborates on model validation steps and concludes with a discussion on addressing concern areas and selecting solutions from one of the case studies.

Model Development Methodology
Model development typically begins with a data gap analysis for inputs such as impervious cover, building footprints, first-floor elevations, pavement edges, storm systems, channel systems, and roadside ditches. Field surveys fill in missing GIS and as-built drawing data. LiDAR data updates are crucial in redeveloped areas or where LiDAR cross-sections are shallower than as-built drawings.

Modeling approaches impact input details, such as detailed breaklines for rain-on-mesh models or runoff catchment delineation for Catchment-Based Hydrology models. The modeling approach selection, guided by project goals and terrain data quality, is critical.

In Catchment-Based Hydrology, runoff calculations at the catchment level, applied to model nodes and 2D meshes, require lower computational needs since most of the 2D mesh remains dry until flooding occurs. This method may oversimplify surface flow routing and depends on accurate catchment delineation and runoff parameters. Conversely, the rain-on-mesh approach directly applies rainfall to the mesh, relying on detailed terrain and land-use data, leading to comprehensive surface flow routes but higher computational demands.

Next, input layers for both 1D and 2D model components are prepared, including storm pipes, 1D open channels, main channels where no crossing structures are needed, and roadside ditches. LiDAR data is crucial for terrain representation and elevational changes. Accurate boundary conditions, including inflows from offsite areas and downstream water levels, are essential for model stability.

Model Validation
Model validation ensures accuracy. When flow data is unavailable, existing flood claims can serve as validation sources. For Houston's stormwater model, three storm events per watershed (selected by flood claims data availability) were used for validation. Hurricane Harvey was universally applied due to its significance. One event was used to validate the closed storm system without receiving channel water elevation impacts.

Validation criteria included a 50% match between flooded structures based on flood claims and model results and a 75% match between flooded parcels based on flood claims and model results. Models showed good alignment with claims data, and flood extents were consistent with claims locations and previous models.

Case Study Results
After validation, models ran seven storm frequency simulations to determine the service level for system components and pinpoint deficiencies. Results identified locations with hydraulic deficiencies due to storm system capacity or receiving channel water elevation, leading to better future solutions.

Conclusion and Lessons Learned
- The 2D model assessed system performance during various design storms.
- High-quality inputs reduced stabilization and validation time.
- Applied initial conditions or baseflow where necessary.
- The 2D model was validated using several historical rain events' flood claims.
- Adequate troubleshooting time is essential.
- Field visits during and after storms confirmed stormwater flooding conditions as part of the validation process.
- Resident input and social media posts during large storms were secondary validation sources.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

13:30:00

13:45:00

Session time

13:30:00

15:00:00

SessionMapping and Modeling Mayhem: A Downpour of Flood Mitigation Solutions

Session locationMcCormick Place, Chicago, Illinois, USA

TopicStormwater

Author(s)

Abdo, Khaled, Gheith, Hazem

Author(s)K. Abdo1, H. Gheith1

Author affiliation(s)Arcadis, Inc.1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160082

Volume / Issue

Content sourceWEFTEC

Word count10

Green Infrastructure Siting Using Robust Efficient Procedure

Abstract

Abstract
Robust siting of Green Infrastructure (GI) application can achieve high reduction in peak discharge rates of runoff during storm events and improve water quality, all while creating additional green space benefits. While designing and implementing GI has become more mainstream, retrofitting GI into developed areas still poses challenges due to existing utilities and infrastructure, lack of suitable soils or suitable slopes, and several other potential surface and subsurface issues. To identify and evaluate favorable potential GI locations, we developed a four step GIS site-screening approach that reduces engineering process and leads to optimized GI application programs. Arcadis developed a GIS site screening approach that uses readily available infrastructure data. Much of this work would have previously been done by sending field staff out to inspect and gather data. The goal of this approach is to provide a tool for the planner/ designer that represents a continuum of GI suitability across the project area from which individual locations are evaluated and ranked before the sites are sent for further field confirmation. This approach reduces time in the field by prioritizing which areas may be better suited for GI implementation and as such can provide a defensible baseline for Capital Improvement Program (CIP) project selection and design. The approach was developed and used successfully in several cities across the US, in Columbus, OH, Los Angles, CA, DC and Richmond, VA.
Objective
The developed approach depends on 4 steps to locate most efficient sites that include flow availability, site availability, site suitability and GI performance scoring. These four steps address the sites secretion, the location of the GI (in public parcels or within the public corridor), the type of GI (Bioretention cells or pervious pavement) existing surface and subsurface utilities and project goals. The objective is to consider all the prementioned factors using readily available data and produce a short list of sites that provide highest benefits and reduces the required flied work Stepping through each phase sequentially enabled the screening of large number of potential public parcels and right-of-way sites and reduce to a viable number of sites with the highest benefits. The evaluation process also enabled the GI Ranking approach to provided results at a faster rate as lesser number of sites are being evaluated in each new phase. Finally, the process helped to simplify reviews for each phase and prevented re-examination of sites that were already excluded if/when the performance criteria was modified Figure 1 shows the workflow diagram of the selection phases and the objective/target of each step.
Methodology
The GI Ranking Tool evaluation and analysis process includes the following steps:
1. Flow Availability. The flow availability process involved locating runoff catchments and city owned parcels with adequate surface runoff. The process included identifying flow routing mechanisms and calculating directly connected impervious area (DCIA) within both City owned parcels and runoff catchments.
2. Site Availability. In this step, the availability for adequate space for various GI types within sites with high flow runoff identified in step 1. Site availability analysis depends on the minimum requirements for each of the considered GI types. In public parcels, pervious pavement, Bioretention cells in open spaces, and/ or converting part of the parking lot to bioretention are considered. In public corridors within the right-of-way, permeable pavement is considered for low traffic areas, like local roads, collector roads, and alleys with curbs. Bioretention sites are considered along sidewalk away from intersections and driveways
3. Site Suitability. Steps 1 and 2 determine the availability of flow to mitigate and space to place GIs. In step 3, sites are then screened for suitability based on potential conflict with surface functions and potential conflict with subsurface structures like tress, utilities, etc.
4. Score GI Performance. The fourth step is ranking the GIs using scoring criteria that meet the study target goals. Criteria include amount of runoff/flow reduction, impervious area reduction, maintenance of the selected GI types, socioeconomic benefits, minimization of known local flooding condition, improvement of urban tree canopy and improvement of water quality. Different benefits could be used for the ranking based on the project goals.
Case Study Results
The siting procedure was applied to different cities Including Columbus Ohio, Los Angles California, DC and Richmond VA. The Richmond, VA GI Master Plan is used in this presentation to detail the procedure. The objective was to identify opportunities to incorporate green infrastructure in public parcels and in the right-of-way to reduce stormwater quantity and improve water quality. The key objectives that are critical to the project's success include: - Reduce stormwater volume in the combined sewer system. - Reduce impervious area and increase green space. - Reduce amount of nitrogen, phosphorus, and sediment delivered to James River. - Address existing drainage/flooding concerns where possible. - Implement easily maintainable GI where possible to minimize future maintenance (since maintenance in perpetuity will be required of any GI). The study area included over 500 public parcels and the impervious area within the public corridor was more than 3,860 acres. The final site selection show that Bioretention in open areas of public parcels and the space between curb and sidewalks in the public right-of-way had the highest number of qualified sites for incorporating GI, while bioretention in parking lots and green alleys had significantly smaller numbers of qualified sites. The public parcels contained 169.75 acres of DCIA. The applied procedure identified the top 110 parcels with the highest score. GI application to these 110 parcels would control up to 154 acres (91%) of the public parcels DCIA. The public corridor contained 3,862 acres of DCIA. The applied procedure identified the top sites with the highest score that would control 536 acres (14%) of the DCIA within the public corridor. Tables 1 through 6 show an example of the siting procedure results for each step and Figures 4 and 5 show an example for the final site selection and ranking.

The proposed GIS site screening approach uses readily available infrastructure data to provide a tool for the planner/designer with continuum of GI suitable sites across the project area. an automated four step GIS site-screening approach that includes the confirmation Flow Availability, Site Availability, Site Suitability and Scoring GI Performance was developed. These steps reduce engineering processes and lead to an optimized GI application program.

SpeakerAbdo, Khaled

Presentation time

08:30:00

08:55:00

Session time

08:30:00

10:00:00

TopicIntermediate Level, Intelligent Water, Stormwater and Green Infrastructure, Watershed Management, Water Quality, and Groundwater, Wet Weather

Author(s)

Abdo, Khaled

Author(s)Khaled M. Abdo1; Hazem Gheith1

Author affiliation(s)ARCADIS U.S., Inc., Columbus, OH1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158484

Volume / Issue

Content sourceWEFTEC

Word count8

Green Infrastructure Siting Using Robust Efficient Procedure

Abstract

Abstract Robust siting of Green Infrastructure (GI) application can achieve high reduction in peak discharge rates of runoff during storm events and improve water quality, all while creating additional green space benefits. While designing and implementing GI has become more mainstream, retrofitting GI into developed areas still poses challenges due to existing utilities and infrastructure, lack of suitable soils or suitable slopes, and several other potential surface and subsurface issues. To identify and evaluate favorable potential GI locations, we developed a four step GIS site-screening approach that reduces engineering process and leads to optimized GI application programs. Arcadis developed a GIS site screening approach that uses readily available infrastructure data. Much of this work would have previously been done by sending field staff out to inspect and gather data. The goal of this approach is to provide a tool for the planner/ designer that represents a continuum of GI suitability across the project area from which individual locations are evaluated and ranked before the sites are sent for further field confirmation. This approach reduces time in the field by prioritizing which areas may be better suited for GI implementation and as such can provide a defensible baseline for Capital Improvement Program (CIP) project selection and design. The approach was developed and used successfully in several cities across the US, in Columbus, OH, Los Angles, CA, DC and Richmond, VA. Objective The developed approach depends on 4 steps to locate most efficient sites that include flow availability, site availability, site suitability and GI performance scoring. These four steps address the sites secretion, the location of the GI (in public parcels or within the public corridor), the type of GI (Bioretention cells or pervious pavement) existing surface and subsurface utilities and project goals. The objective is to consider all the prementioned factors using readily available data and produce a short list of sites that provide highest benefits and reduces the required flied work Stepping through each phase sequentially enabled the screening of large number of potential public parcels and right-of-way sites and reduce to a viable number of sites with the highest benefits. The evaluation process also enabled the GI Ranking approach to provided results at a faster rate as lesser number of sites are being evaluated in each new phase. Finally, the process helped to simplify reviews for each phase and prevented re-examination of sites that were already excluded if/when the performance criteria was modified Figure 1 shows the workflow diagram of the selection phases and the objective/target of each step. Methodology The GI Ranking Tool evaluation and analysis process includes the following steps: 1. Flow Availability. The flow availability process involved locating runoff catchments and city owned parcels with adequate surface runoff. The process included identifying flow routing mechanisms and calculating directly connected impervious area (DCIA) within both City owned parcels and runoff catchments. 2. Site Availability. In this step, the availability for adequate space for various GI types within sites with high flow runoff identified in step 1. Site availability analysis depends on the minimum requirements for each of the considered GI types. In public parcels, pervious pavement, Bioretention cells in open spaces, and/ or converting part of the parking lot to bioretention are considered. In public corridors within the right-of-way, permeable pavement is considered for low traffic areas, like local roads, collector roads, and alleys with curbs. Bioretention sites are considered along sidewalk away from intersections and driveways 3. Site Suitability. Steps 1 and 2 determine the availability of flow to mitigate and space to place GIs. In step 3, sites are then screened for suitability based on potential conflict with surface functions and potential conflict with subsurface structures like tress, utilities, etc. 4. Score GI Performance. The fourth step is ranking the GIs using scoring criteria that meet the study target goals. Criteria include amount of runoff/flow reduction, impervious area reduction, maintenance of the selected GI types, socioeconomic benefits, minimization of known local flooding condition, improvement of urban tree canopy and improvement of water quality. Different benefits could be used for the ranking based on the project goals Case Study Results The siting procedure was applied to different cities including Columbus Ohio, Los Angles California, DC and Richmond VA. The Richmond, VA GI Master Plan is used in this presentation to detail the procedure. The objective was to identify opportunities to incorporate green infrastructure in public parcels and in the right-of-way to reduce stormwater quantity and improve water quality. The key objectives that are critical to the project's success include: - Reduce stormwater volume in the combined sewer system. - Reduce impervious area and increase green space. - Reduce amount of nitrogen, phosphorus, and sediment delivered to James River. - Address existing drainage/flooding concerns where possible. - Implement easily maintainable GI where possible to minimize future maintenance (since maintenance in perpetuity will be required of any GI). The study area included over 500 public parcels and the impervious area within the public corridor was more than 3,860 acres. The final site selection show that Bioretention in open areas of public parcels and the space between curb and sidewalks in the public right-of-way had the highest number of qualified sites for incorporating GI, while bioretention in parking lots and green alleys had significantly smaller numbers of qualified sites. The public parcels contained 169.75 acres of DCIA. The applied procedure identified the top 110 parcels with the highest score. GI application to these 110 parcels would control up to 154 acres (91%) of the public parcels DCIA. The public corridor contained 3,862 acres of DCIA. The applied procedure identified the top sites with the highest score that would control 536 acres (14%) of the DCIA within the public corridor. Tables 1 through 6 show an example of the siting procedure results for each step and Figures 4 and 5 show an example for the final site selection and ranking.

This paper was presented at the WEF Collection Systems Conference in Detroit, Michigan, April 19-22.

SpeakerAbdo, Khaled

Presentation time

8:30:00

9:00:00

Session time

8:30:00

10:00:00

Session number6

Session locationHuntington Place, Detroit, Michigan

TopicCombined Sewer System, GIS, Green Infrastructure

Author(s)