2021 Annual Meeting Abstracts
Many thanks to the Zone X Sponsors
TUESDAY – APRIL 13, 2021
7:30 am – Virtual Room opens
8:00 am – 8:30 am PLENARY SESSION Speaker: The Honorable Charles Perry Texas State Senator, District 28 Presentation: Update from the State Legislature
8:45 am – 9:40 am Speakers: Tyler Payne, PMP; Colleen Jones Texas General Land Office
Presentation: Regional Flood Studies and Interagency Grants The Texas General Land Office Community Development and Revitalization (GLO-CDR) Planning team designs and oversees planning studies to collect, analyze, and communicate disaster-related data to assist decision makers to better protect Texans from future disasters. GLO-CDR recently implemented the Combined River Basin Flood Studies, detailing flood risk information and mitigation strategies for disaster-impacted counties impacted by Hurricane Harvey. Additional funding is being directed toward interagency grants with the Texas Water Development Board (TWDB), US Army Corps of Engineers (USACE), and US Geological Survey (USGS) for the creation of a team of industry experts to assess and develop potential flood models that will build a comprehensive framework for evaluating flood risks. Finally, through an additional interagency grant, Texas University A&M Systems (TAMUS) is developing a system capable of housing, securing, and displaying the state’s disaster data needs. Learn how these interrelated initiatives will help inform communities to mitigate against future disasters.
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9:55 am – 10:50 am Speakers: Saul Nuccitelli, PE, CFM; Reem Zoun, PE, CFM Texas Water Development Board Presentation: TWDB Flood Rish Reduction Effort Update The 86th Texas Legislature passed, and Governor Abbott signed, Senate Bill 500 which appropriated $47,000,000 from the floodplain management account in the Texas infrastructure resiliency fund to the TWDB for developing or updating flood risk maps in the state to support development of a state flood plan. This presentation will cover the upcoming mapping initiatives, regional flood planning and state flood planning activities by the Texas Water Development Board.
10:50 am – 11:00 am BREAK
11:15 am – 12:15 pm General Membership Meeting Presenters: John Espinoza, PE, CFM – TFMA President Stephanie Griffin, PE, CFM – TFMA Treasurer Wes Birdwell, PE, CFM – TFMA Executive Director 12:15 pm – 12:45 pm – REMO Networking 1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK A – DRAINAGE/STORMWATER MANAGEMENT
1:00 pm – 1:30 pm A1 Ranking of Potential Sites for Stormwater Best Management Practices Speakers: Yu-Chun Su, Ph.D., P.E., CFM, CPESC, CPSWQ; Lockwood, Andrews & Newnam, Inc. Michelle Garza; San Antonio River Authority Ka Leung Lee, PhD., PE, CFM, CPSWQ; Lockwood, Andrews & Newnam, Inc.
Presentation: A stormwater Best Management Practice (BMP) performance evaluation HSPF modeling project was conducted under the Upper San Antonio River (USAR) Watershed Protection Plan Implementation (WPPI) – Green Stormwater Infrastructure (GSI) Master Plan Data Acquisition, Modeling, and Geospatial Quality Assurance Project Plan. This effort was funded in part by the United States Environmental Protection Agency federal Clean Water Act 319(h) funds through the Texas Commission on Environmental Quality (TCEQ) and the San Antonio River Authority (SARA). BMP evaluation and associated HSPF modeling effort was conducted by Lockwood, Andrews & Newnam, Inc. (LAN).
To assist with the selection of BMP sites that are most suitable for modeling and performance evaluation, a BMP ranking matrix was developed using MS Excel. This ranking matrix is the first of its kind in San Antonio and it greatly helped with evaluation and selection of BMP sites within a water quality modeling subbasin. The developed BMP ranking matrix involves assigning scores to key factors such as drainage area, land uses, BMP footprint area, receiving water, BMP types, shading, floodplain, soil types, etc. The ranking matrix is set up so each of the scores in the matrix is multiplied by a weighing factor when calculating the “Overall_Score”. The weighing factors are located in the “Weights” row with default values of 1.0, and SARA and other potential users can adjust the values higher or lower as they see fit.
The results of the BMP ranking analysis were used to support BMP performance evaluation modeling for estimating annual average load removal at each BMP site and the effectiveness of BMP in reducing constituent loads. The target constituents are E. coli and nutrients. This presentation will cover the development, application, and findings of the BMP ranking matrix.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK A – DRAINAGE/STORMWATER MANAGEMENT
1:45 pm – 2:15 pm A2 – Smart LOF Analysis – Using the Past to Guide the Future Speakers: Matt Stahl, P.E., CFM; Halff Associates Cooper Hoffman, EIT, CFM; Halff Associates Cannon R. Henry, P.E., CFM; City of Fort Worth Presentation: This presentation will discuss the ‘Smart LOF’ (Smart Likelihood of Failure) analysis and how we envision it adding value and lowering the cost of storm drain rehabilitation and asset management. Smart LOF analysis allows cities to harness immense amounts of condition assessment data with asset-level granularity through a process that guides decision-making to prioritize revitalization and rehabilitation of aging infrastructure.
The City of Fort Worth is entering its second operational year of a comprehensive Storm Drain Rehabilitation Program (SDRP) that is managed by the Transportation and Public Works Department, Stormwater Management Division. During Year 1 (FY20), 18+ miles of storm drain were CCTV inspected, imported to GIS, and evaluated for corrective actions. The City’s goal is to inspect and evaluate 25+ miles of storm drain in Year 2 (FY21) and beyond.
Halff Associates assisted the City of Fort Worth with the SDRP Program development and implementation from FY19 to FY21. After the first full year of the program, Halff identified an opportunity for the City to harness the GIS, Risk, and CCTV datasets generated by the SDRP Program to better understand the critical and complex problems related to storm drain operations, maintenance, and repair. Halff independently developed and carried out a machine learning analysis that the City may implement in the future to better inform decisions and spending on condition assessment and capital projects. This type of analysis can be used to effectively model likelihood of failure for utility datasets that meet specific criteria. A supervised machine learning approach enabled us to leverage a relatively small subset of field data (~5% of system) to approximate condition for the rest of the system with a True Positive hit rate of 70-80%. The approach can also pinpoint trends and patterns that aren’t readily apparent through traditional summary statistics and observations.
2:30 pm – 3:00 pm A3: Salado Creek Watershed – Hydrologic Updates and Karst Interactions in the San Antonio River Basin Speakers: Rebecca Katz, PE, PMP, CFM, ENV SP; Atkins Lukas Godbout, EIT; Atkins Presentation: The San Antonio River Authority (SARA) is performing floodplain mapping updates for the major watersheds in Bexar County. The updates include new hydrologic modeling standards which will be incorporated in a future update of the San Antonio River Basin Regional Modeling Standards for Hydrology and Hydraulic Modeling. Major hydrologic modeling changes include revisions to loss methods from SCS Curve Number method to Green and Ampt to better account for karst terrain within the river basin. Atkins was contracted to perform mapping and modeling updates for the Salado Creek watershed. A large portion of the 223 square mile watershed is located within the Edwards Aquifer. Subsurface interactions through karst terrain and artesian areas have significant impacts on the riverine hydrology but were not accounted for in the effective 2010 hydrologic models. Review of historical gage data along the Salado Creek mainstem indicate that recorded peak flows include high variability with up to 75% downstream peak flow reduction over 13 river miles for the May 2013 storm event.
This presentation will discuss the hydrologic modeling and calibration efforts in the watershed. Topics will also include calibration challenges encountered due to limited historical gage data, rapid urbanization, and aquifer interactions to surface flow. Additional topics include: • Major changes to SARA hydrologic modeling methodology • NOAA Atlas 14 update • Karst aquifer considerations • Draft Salado peak flow information
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK A – DRAINAGE/STORMWATER MANAGEMENT
3:15 pm – 3:45 pm A4: Master Planning & Detention in Established Neighborhoods – The University Park Experience Speakers: Katie Barron, PE, ENV SP; City of University Park Hamilton Dallagasperina, PE, CFM; Huitt-Zollars Gabriela Bell, PE, CFM; Huitt-Zollars Presentation: Reducing flood risk in older, established neighborhoods that were designed to less stringent criteria than is common today can be challenging. Developing a clear understanding of the existing conditions is key. Out-side-the-box thinking can also be critical to developing cost-effective solutions. We will examine master-planning efforts, discuss underground detention design, and display time-lapsed construction videos. We will also discuss project management and project delivery alternatives from the City Engineer perspective.
4:00 pm – 4:30 pm A5: Pecan Creek Watershed Study: Practical Solutions to Urban Flooding in Denton, TX Speakers: Michael D. Smith, PE, CFM; City of Denton Ashley Lowrie, PE, CFM; Halff Associates Joshua McClure, PhD, PE, CFM, PMP; Halff Associates Presentation: The City of Denton has experienced multiple flood events along Pecan Creek and North Pecan Creek, including in 2020. This has resulted in extensive flood damage to residential, commercial, and municipal structures. Despite NRCS dams upstream, the urbanized corridor and historic channelization through the city center have often been inadequate to convey floodwaters. This has resulted in over 290 structures located within the 1% ACE (100-year) floodplain footprint along both Pecan and North Pecan Creek, many of which have experienced flood damage. Halff Associates, Inc. evaluated the existing floodplain conditions and developed updated floodplain maps for the watershed. Based on this updated modeling and mapping, multiple floodplain mitigation measures were considered, including bypass systems, increased channel capacity, enclosing the open channel in pipes, expanding bridges and culverts, and regional detention.
The goal of this alternatives analysis was to identify alternatives that would reduce the flood risk of the 1% ACE (100-year) along North Pecan and Pecan Creek upstream of Woodrow Lane. Through rapid screening of alternatives, the comprehensive list of potential mitigation projects was reduced to a list of five alternatives selected for more detailed consideration including detailed flood mitigation potential, cost estimation, and project scoring. Regional detention proved to be the most impactful, and when combined with strategic conveyance improvements, over 100 structures could be removed from the 1% ACE (100-year) floodplain. Consideration was given to permitting feasibility, constructability, availability of land, and other practical considerations. City staff are evaluating these alternatives and the various funding options available to implement them.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK B – Technical H & H
1:00 pm – 1:30 pm B1: Saving $$ by NOT Modeling Stream Crossings Within 2D Models Speaker: Sravan Krovidi, PE; Atkins
Presentation: With the advent of HEC-RAS 5.0 version, Two-Dimensional modeling has gained popularity amongst the general modeling community and end users as well. As HEC continues to enhance the features and modeling capabilities including adding structure crossings of culverts and more recently bridges (RAS 6.0 Beta version), the 2D modeling will be the go-to for modeling solutions. Typical watershed will have obstructions to flow in form of road crossings, which range from small dirt crossings to large interstate systems and not to forget rail-road crossings. These stream crossings take a lion share of the modeling work including gathering of the crossing data that may require field survey data, which is an expensive task.
The 2D models can offer a hidden benefit of not modeling these stream crossings altogether via hydro-enforcing the terrain data to represent the opening, where higher level of modeling accuracy is not required (typically BLE / Zone A studies). This will not only improve the stability of model but also can speed-up the modeling efforts, therefore increasing the quality while reducing the costs. This presentation aims to set basic calibration criteria of a stream crossing based on the design plans and conveyance capacities of the openings by utilizing HY-8 and also 1D modeling outputs to help burn the terrain with appropriate size and verify the head and tailwaters at the crossings.
1:45 pm – 2:15 pm B2: Water for Ducks Unlimited: Restoring Endangered Coastal Prairie with HEC-RAS 2D Speakers: Garrett Johnston, PE, CFM, GISP; Freese & Nichols Andrew Swynenberg, PE; Freese & Nichols Woody Woodrow, Fish & Wildlife Biologist; U.S. Fish & Wildlife Sciences
Presentation: Through a partnership between the U.S. Fish and Wildlife Service, Ducks Unlimited, and Danbury Drainage District, with support from National Fish and Wildlife Foundation’s Gulf Environment Benefit Fund, Freese and Nichols, Inc. (FNI) used HEC-RAS 2D to analyze several wetlands restoration alternatives for Chocolate Bay Prairie Unit wetlands within the Brazoria National Wildlife Refuge.
Under existing conditions, several manmade flood control ditches within the 20-square-mile Unit intercept the natural runoff patterns from the landscape and convey it to Chocolate Bay, depriving historical wetlands in the Unit from freshwater flows. Structures and berms simultaneously alter water flow and promote prolonged flooding at other locations within the unit. FNI developed multiple two-dimensional, rain-on-mesh hydraulic models of approximately 50 square miles that include the Unit and surrounding area. The use of HEC-RAS for 2D modeling allowed for a detailed depiction of existing flow patterns throughout the site and pointed to the most efficient locations for potential restoration alternatives.
FNI evaluated several alternatives involving site grading, culvert construction, and barrier removal to restore historic freshwater flows into the wetlands. These alternatives were designed to maintain existing ditch capacity and avoid adverse flooding impacts for adjacent roadways and property owners. HEC-RAS was used to evaluate the efficacy of each wetlands restoration alternative and show no adverse impacts using multiple metrics available through RAS Mapper.
This presentation will include an overview of the project and detailed discussion of the modeling approach and results. This approach has provided essential guidance in developing wetland enhancements that create a more self-sustaining landscape that supports wetland habitats and associated wildlife species, with little additional management required from the refuge. This approach may be helpful in planning similar wetland enhancement or restoration efforts.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK B – TECHNICAL H & H
2:30 pm – 3:00 pm B3: Nationwide (USA) Pluvial Flood Modeling via Telemac2D Speaker: Sarada Kalikivaya, PE, PMP, CFM; Atkins Max Kipp, PE, CFM; Atkins Presentation: FEMA has estimated that approximately 40% of flood damages are due to pluvial flooding, which occurs when locations with small drainage area experience excessive accumulation of direct rainfall runoff. These floods are typically shallow and low-velocity, but can cause significant damage and disruption. In 2018, Atkins developed an automated workflow to run pluvial models en masse, using Telemac2D as the model engine. Telemac2D is FOSS maintained by a consortium of EU and UK organizations.
Atkins first piloted the workflow in South Carolina before applying it to vast areas of the United States (anywhere that high resolution ground DEMs were available). The total modeled area to-date is about 1.7 million square miles, covering about 82% of the population of the USA, including portions of 50 states, DC, and major territories. Each state was broken into small independent basins and covered by a triangulated mesh, with node spacing between 11 and 15 meters. A 6-hour nested hyetograph was generated at each node using NOAA data, for four events: 2yr, 10yr, 100yr, and 1000yr. Basins were processed in parallel via cloud computing (Google Compute Engine), with concurrent CPUs as high as 5,000 physical cores’ equivalence, allowing speeds of about one USA state per day. Final depth rasters have 3-meter pixels and are approximately 8 terabytes, compressed.
In 2020, this project was selected as one of three finalists in the UK Environment Agency’s Flood & Coast Excellence Awards, in the Digital Excellence category, and received a Highly Commended Certificate.
Thank you to our Zone AE Sponsors:
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK B – TECHNICAL H & H
3:15 pm – 3:45 pm B4: North Houston Highway Improvement Flood Planning Study (Segment 2) Speaker: Scott Hughes, PE ,CFM; CivilTech Engineering Inc.
Presentation: The NHHIP is slated to be the biggest construction project in this generation for the Houston area. The scope of the project is huge, it entails widening the North Freeway, I-45, from the North Sam Houston Tollway to Downtown Houston. The project is intended to help Houston deal with its expanding population and continually greater infrastructure needs by better managing traffic congestion, enhancing safety, and improving mobility and operational efficiency in downtown Houston.
The NHHIIP project crosses or runs adjacent to three major City of Houston Bayou systems: Buffalo Bayou, White Oak Bayou and Little White Oak Bayou. CivilTech working with TxDOT took a non-standard approach to evaluating the drainage impacts associated with the NHHIP project. Switching from focusing on addressing the drainage components of the project within TxDOT ROW, TxDOT and CivilTech approached the project from a holistic perspective and considered how this signature project could benefit the City outside of improving traffic mobility. CivilTech developed a complex dynamic hydrologic and hydraulic model utilizing the unsteady flow capabilities of HEC-RAS. The HEC-RAS model include the three bayou systems, Buffalo Bayou, White Oak Bayou, and Little White Oak Bayou and encompasses approximately 73 square miles. The model was verified against high water marks from recent historical storm events including the April 2016 Tax Day event and the August 2017 Harvey event. Part of the holistic approach included coordination with other local governmental agencies with interest in the project, including the COH and HCFCD.
4:00 pm – 4:30 pm B5: The Boerne Identity: Future Proofing Growth and Preserving Riparian Resources Speakers: Troy Dorman, PhD, PE, CFM; Halff Associates Jeff Carroll, PE; City of Borne Josh Logan, PE, CFM; Halff Associates Presentation: The City of Boerne is nestled in the heart of the Texas Hill Country surrounded by scenic natural areas. First settled in the 1800s, Boerne has a charming and historic downtown/Main Street area that runs alongside Cibolo Creek. Abundant natural amenities, a charming small- town atmosphere, parks and trail systems, excellent schools, and easy access to employment centers have prompted a substantial increase in growth for Boerne.As Boerne, Texas (population 20,000) has doubled in size over the last 10 years there has been a growing concern about impacts of new development.
Located in the desirable Hill Country and also in Flash Flood Alley, citizen groups have encouraged the City to implement a proactive plan that guides growth in a way that is both fiscally and environmentally sustainable. With City Council leadership, the City of Boerne recently updated their stormwater regulations to achieve better flood protection and water quality outcomes with an eye towards preserving the Cibolo Creek and its tributaries for future generations. The process was an outgrowth of the City’s 2018 Comprehensive Master Plan that identified the streams as a core feature of the city’s fabric. The process resulted in revision of Boerne Subdivision Code Articles 3 and 6 to incorporate a citywide water quality standard, a higher standard for flood protection, stream buffers, and enhanced local floodplains to protect future development areas. The new code also incentivizes trails and active recreation within the protected stream buffers to enhance the community.
The result was an integrated stormwater management code that is a comprehensive water quality and detention ordinance with enhanced flood protection for watersheds with a 25-acre or larger contributing area. This presentation will cover how the City arrived at the desired quality of life goals and how the ordinance was developed to reach many of the concurrent goals.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK C – DISASTER RECOVERY\FLOOD WARNING
1:00 pm – 1:30 pm C1: Developing Sustainable Flood Warning Systems Speakers: David C. Curtis, PhD, F.EWRI; West Consultants Lee von Gynz-Guethle, PE, CFM; West Consultants Presentation: Flood Warning Systems represent an opportunity for local communities to reduce flood risk without major investment in infrastructure. It can also provide a better understanding of how and when flooding occurs, which translates to more effective flood mitigation efforts in the future. However, to achieve these long-term benefits, Flood Warning Systems require holistic planning and a strategic long-term vision. Since significant floods occur aperiodically, it is good practice to develop the system of data collection and decision support to benefit a broader constituency than just the flood impacted. Between October and December 2020, the Texas Water Development Board (TWDB) awarded $X.XMM to rural cities and counties for Flood Warning Systems, including gages, low water crossing flashers, communication towers, and software. To support this investment, it is important to coincidentally develop long-term operations and maintenance strategies, integration into response planning, inter-operability between adjacent systems, and implementation of robust training programs.To better support local communities, we endorse the idea that TWDB create a long-term, state-wide program to support the effective and consistent planning, operation, and maintenance of Flood Warning Systems.
In this presentation, we will discuss why we believe this is critical and how such a program could be structured. We will also discuss the basic components of Flood Warning Systems and how holistic planning and vision is critical to long-term success.
1:45 pm – 2:15 pm C2: Developing a Semi-Realtime Urban Flood Webmap for the City of Sugar Land Speakers: Johnny Kim, PE, CFM; Halff Associates Jorge Alba; PhD, PE, CFM; City of Sugar Land Sam Hinojosa, PE, CFM; Halff Associates
Presentation: In the wake of several flooding events in recent years, including the May 7, 2019 event, the City of Sugar Land moved forward on an effort to study the potential urban flood risk citywide and to communicate that risk in semi-real time through a publicly available webmap. The study included the following objectives: • Generate Atlas 14 ponding maps of various storm durations and frequencies for citywide coverage • Develop a webmap that displays ponding maps that correlate with live rainfall gauge data
The study team obtained 11 detailed 1D and 2D hydraulic models (InfoWorks ICM and HEC-RAS) that were previously developed for the City. and simulated Atlas 14 rainfall was simulated in these models for various storm durations (1-hour to 24-hour) and frequencies (2-year to 500-year). An approximate 2D model was developed in ICM to estimate ponding in the remaining portions of the City that were not included in a detailed model. The model results were cataloged in GIS as rasters and clipped for 27 different zones representing the rainfall gages within the City. The study team developed a webmap that retrieves stream elevation and rainfall accumulations every five minutes from the available City gages. For each gage, accumulated rainfall depths are evaluated for various time intervals (the past 1-hour to 24-hour), and the most critical storm ponding raster is automatically selected and displayed on the webmap for each gage zone. The webmap also displays live stream elevations from available gages and rainfall radar from the National Weather Service.The webmap has an additional “predictive” tool for the City, which allows a user to input forecasted rainfall depths. The webmap selects and displays the ponding map that is most closely associated with the inputted rainfall depth and duration.
This presentation will provide an overview of the detailed and approximate H&H methods used to produce the catalog of ponding maps. In addition, a live demonstration of the webmap will be provided. The presentation will also include how the City intends to use the new tool to enhance flood response during storm events.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK C – DISASTER RECOVERY\FLOOD WARNING 2:30 pm – 3:00 pm C3: Raleigh, North Carolina Flood Early Warning System Speakers: Chris Stanley, PE, CFM; McAdams Kelly Daniel; City of Raleigh, NC Ben Wostoupa, PE; Vieux & Associatesl Presentation: With the increased frequency of flash flood-producing storm events in recent years impacting all communities and a greater need for advanced warning to plan and prepare for this flood risk, the City of Raleigh is currently in the advanced stages of development of its own Flood Early Warning System. Ultimately, the City desires the ability to provide advance prediction of potential stream flooding and increased lead time for public notification, road closures, and (if necessary) evacuation. Phase 1 of this project was completed in late 2020, and included the development of a pilot study to create a Flood Early Warning System for the upper portions of the Crabtree Creek watershed, from just downstream of Lake Crabtree to the stream’s crossing at US Highway 1/Capital Boulevard. This includes analysis and incorporation of predictive flood alert notifications for known problem areas within this watershed, including existing flooding “hot-spot” locations near Crabtree Valley Mall as well as near the intersection of Wake Forest Road and Six Forks Road. The Flood Early Warning System will also incorporate the use of Gauge Adjusted Radar Rainfall (GARR) to better predict and measure rainfall intensity across the pilot basin study, as well as will utilize high-resolution modeling of flash floods to provide a more accurate picture of the risk to critical assets and increase lead time for first responders to aid in public safety and protection.
This project is being led by Flood Warning System development experts Vieux & Associates, who also developed a similar system for the City of Austin, Texas in 2017. This presentation will cover some of the highlights of Austin's system as well as lessons learned, efficiencies developed, and refinement of data through hot spot analyses and local flooding knowledge with locally based engineering firm McAdams for development of the City of Raleigh's system. This pilot study is also being conducted in cooperation with USGS to use existing stream gauge equipment to aid in the development of the flood early warning system for better forecast analysis and prediction of flood stages.
Ultimately, the results from this program will offer increased lead time to notify first responders and the greater public within the City of Raleigh about storm and flood risk/impacts.
3:15 pm – 3:45 pm C4: Lower Colorado River Flood Warning: A Response to Harvey Speaker: Daniel Harris, PE, CFM; Scheibe Consulting, LLC Eric Scheibe, PE, CFM; Scheibe Consulting, LLC
Presentation: The Lower Colorado River was heavily impacted during Hurricane Harvey. Flood losses in Colorado County and Wharton County were high, with large portions of urban centers flooded for days. The event was extreme and revealed deficiencies in the current understanding of how the Lower Colorado River functions during extreme conditions. Local emergency managers scrambled to respond with the information they had, but in some instances, this resulted in communities being evacuated that did not flood and other communities not evacuated that did flood. After the flood waters receded, the local communities decided to combine forces and tackle this situation head-on. Through the joint resources of Colorado Co., Wharton Co., Matagorda Co., City of Columbus, City of Wharton, City of Bay City, and the Texas Water Development Board, the Lower Colorado River Flood Warning Project (aka “Tri-County” Study) was formed.
This study includes three main goals. 1) Enhance the current understanding of the flood hydraulics of the Lower Colorado River, 2) Develop a comprehensive flood inundation library for incorporation into the USGS’s recently developed Flood Decision Support Toolbox. 3) Identify locations within the lower watershed that require additional river gauges needed for enhanced flood warning. This project is an example of a grass- roots effort to solve a regional flood problem and has resulted in significant stakeholder coordination with the LCRA, USACE-Fort Worth District, USACE-Galveston District, USGS, NWS, and the HGAC.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK C – DISASTER RECOVERY\FLOOD WARNING
4:00 pm – 4:30 pm C5: A Presentation for Engineers Who Can't Talk Good & Who Want to Learn to do Other Stuff Good Too Speakers: Niraj Acharya, PE, CFM; Teague Nall and Perkins (TNP) Audra Valamides, PE, CFM; City of Arlington Lee Jeffrey, PE, CFM; City ofArlington Presentation: The construction of floodplain and drainage improvements often impacts landowners who are not familiar with the technical nuances of such projects. Efforts to inform the public about specific projects and overall program goals often involve relating complex technical subjects to everyday life for residents. Municipalities communicate through letters, social media, large public meetings, and small one on one meetings in order to garner public trust and support. The success of any of these forms of communication is contingent upon the ability of the project team to communicate in a manner that is simple and easily digestible by residents.
This presentation will discuss techniques and lessons learned in communicating project benefits and impacts to affected property owners.
1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK D – FLOOD MITIGATION
1:00 pm – 1:30 pm D1: Use of Flood Damage Centers to Maximize Benefits and Create Equitable Solutions Speaker: Scott Rushing, PE, CFM; Halff Associates Chris Tralmer, EIT, CFM; Halff Associates Presentation: This presentation will discuss an equitable approach to identify high flood risk areas, establish relevant evaluation criteria and weighting factors, and perform an objective prioritization of the damage centers. Case studies will be explored to show how damage centers served as an effective tool in developing project recommendations and were used as a screening tool to guide decision-makers and stakeholders in programs such as master planning and feasibility studies.
Limited funding for flood control and drainage projects has made identifying areas most impacted by flood damages even more of a priority. By focusing on these areas, the benefits from drainage improvements can be maximized and the most vulnerable areas addressed. Furthermore, planning studies do not always have a budget and schedule for extensive development of new flood risk and damage data; sometimes we must leverage previous modeling to provide recommendations to decision-makers and stakeholders.
Using predicted flooding metrics, such as number of flooded structures and instances of flooding over a specific time period, damage centers or flood prone areas can be effectively identified locally as well as across large regions. Subsequently, evaluation criteria can be selected to facilitate a comprehensive prioritization based on client and location specific considerations that can include flood risk reduction, socioeconomic indicators, and other factors. There has been a renewed focus to move beyond solely using the traditional benefit-cost ratio to determine if projects should move forward. Equally important to the identification of damage centers is the determination of how to use them to develop and prioritize drainage projects and to create comprehensive CIP programs that maximize the benefit of limited public resources.
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK D – FLOOD MITIGATION
1:45 pm – 2:15 pm D2: Flooding Mitigation in Corpus Christi Speakers: Thomas Mountz, PE, CFM; Lockwood, Andrews & Newnam Laura Casset, PE, CFM; Lockwood, Andrews & Newnam Presentation: The City of Corpus Christi has recently experienced major storm flooding for multiple events including Hurricane Harvey. LAN provided a comprehensive flood analysis of one of the major watersheds within the City and provided improvement recommendations to Major Ditches and Waterways. From this study, the City secured approximately $25 million in grants to provide flood mitigation and detention to the two most impacted areas on and adjacent to the Airport Channel No. 1.
For the next step in the planning-design-construction process for these two interrelated projects, LAN was contracted by the City to update and develop a detailed plan for the proposed improvements. Project #1 is the addition of culverts at the Airport Channel crossing of South Padre Island Drive. SPID is a TXDOT 8-lane major expressway through Corpus Christi. Project # 2 is a proposed 1800 ac-ft. detention reservoir at the confluence of LaVolla Creek and the Airport Channel #1.
This presentation will discuss the results of the detailed model and mapping analysis performed to begin the project design process for these projects. The models were updated to a more detailed terrain based on 2018 LiDAR and an integrated HEC-RAS 2D analysis of the existing flooding, proposed channel improvements, and diversion into the proposed detention pond.
1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK D – HARRIS COUNTY FLOOD CONTROL DISTRICT UPDATES
2:30 pm – 3:00 pm D3: MAAPnext – Development of Modern Flood Risk Communication Tools and Best Practices Speakers: Brian Edmondson, PE, CFM; Harris County Flood Control District Presentation: The Harris County Flood Control District (Flood Control District) and the Federal Emergency Management Agency (FEMA) are partnering to deliver Harris County MAAPnext, or the Modeling, Assessment and Awareness Project (MAAPnext). This project represents a transformative step in the definition, management, and regulation of Harris County’s floodplains, further contributing to our county’s resilience. The complexity of flood risk and finding the right tools communicate it has long been a known issue to the District. With MAAPnext the Flood Control District is taking the opportunity to develop and implement new communication tools and tactics that will empower our citizens with the results of MAAPnext and at the same time equip them with the knowledge to use the results to make decisions. This presentation will cover the best practices and the tools and tactics developed to support flood risk communications include a new interactive dashboard developed on the ESRI Experience Builder platform
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1:00 pm – 4:30 pm CONCURRENT SESSIONS TRACK D – HARRIS COUNTY FLOOD CONTROL DISTRICT UPDATES
3:15 pm – 3:45 pm D4: Completing the Flood Risk Map – An Urban Flood Pilot Study Speakers: Todd Ward, PE, CFM; Harris County Flood Control District Larry Voice, PE, CFM; FEMA, Region 6 Presentation: An ongoing floodplain restudy in Harris County, MAAPnext, will provide a better understanding of flood risk throughout Harris County. This effort will yield modernized flood risk products, the majority of which aim to quantify the riverine flood risk posed by channels spilling out of banks and impacting people and structures located in the affected areas. Additional work is ongoing as part of the MAAPnext effort to generate rain-on-grid flood risk products which consider some urban flooding factors but do have limitations in that not all underground features may be included.
The Federal Emergency Management Agency (FEMA) and Harris County Flood Control District are working on a pilot study to compare rain-on- grid results with those generated from more detailed models that include sub-surface drainage, to use that comparison to determine what factors most contribute to urban flood risk, to recommend an approach to identifying areas at increased risk of urban flooding without highly detailed models, and to develop a strategy to communicate this flood risk information to decision makers in the community to empower them with the knowledge necessary to reduce the risk of flooding.
4:00 pm – 4:30 pm D5: Watershed Master Planning on a Budget – Feasibility Studies of Large Watersheds Speakers: Gary Bezemek, PE; Harris County Flood Control District Presentation: Harris County is an approximately 1,700 square mile county that can be described as flat and floodprone. HCFCD has conducted a series of watershed studies intended to identify the flooding potential in the watershed, and then to identify long term and short projects to reduce flood risk. HCFCD has developed a process that we follow when conducting these projects. This presentation will focus on a specific watershed study to highlight the process we follow, the metrics we calculate to rank and score our projects, the technical tools and assumptions we use, and the special considerations we follow to coordinate our findings with the general public.
Thank You To Our Floodway Sponsors
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WEDNESDAY – APRIL 14, 2021 PLENARY SESSION 8:00 am – 8:30 am Speaker: Charlie Cook, CFM; FEMA, Region 6 Presentation: FEMA Region 6 Floodplain Management & Insurance Branch Chief Charles Cook will discuss FEMA priorities for stopping the cycle of flood damage. Mr. Cook will address substantial damage and repetitive loss which are the most damaged and most at risk properties that will continue to flood over and over until they are mitigated. But more than just at risk properties, he will address at risk people. Equity in floodplain management and insurance, safe and affordable housing, disaster grants and the little know obtain and maintain flood insurance requirement will be covered.
8:45 am – 9:45 am Speaker: Ataul Hannan, PE, CFM; Harris County Flood Control District Presentation: With the increasing abilities provided to the hydrologist through the use of better technology, it has now become possible to link various programs to map flooding events in real-time. Currenttly, the Harris County Flood Control District (HCFCD) developed an in-house tool for the purpose of monitoring flood events as they happen. The product includes links between rainfall information from gages, hydrologic and hydraulic models, and GIS mapping in an effort to transfer incoming rainfall data into expected flood inundation maps.
It is the ultimate goal of this project to continuously update the hydrologic and hydraulic models used in this system to allow the HCFCD to identify the effectiveness of various flood control projects in the Houston metropolitan area. When further linked to structure inventories developed by the HCFCD, this tool aid in rapidly defining an estimate of the number of structures potentially damaged during a flood.
The purpose of this paper is to present information that can be gained from a near real time mapping program such as the one described, as well as to gain understanding of the technology and capabilities that are currently available for the purpose of developing better floodplain management tools and practices.
10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK E - DAMS
10:00 am – 10:30 am E1: You Cannot Improve If You Do Not Measure - Low Head Dams Speaker: Chad Ballard, PE, CFM, ENV SP; Plummer Associates Presentation: Low head dams are normally viewed by many as a small structure in a waterway. What is often overlooked is the dangerous hydraulic conditions that can occur during moderate to high runoff events. These hydraulic conditions can create a countercurrent downstream of the dam which even strong swimmers or people with a personal floatation device have drowned. The exact number of these dams along with the deaths and near-drownings associated with them are not really known since there is a lack of data making this difficult to track. What we do know is that there are deaths caused directly by these structures and they will continue to be a public safety hazard in the future.
The purpose of this presentation is to learn about what a low head dam is, what conditions make them so dangerous, what can be done together to help solve the problem and what obstacles are to be overcome to arrive at this solution.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK E – DAMS
10:45 am – 11:15 am E2: Dredging White Rock Lake - A Feasibility Study Speakers: Patrick Miles, PE; Freese & Nichols David Phan, PE, CFM; City of Dallas Presentation: The feasibility study evaluated dredging scenarios to remove accumulated sediment in White Rock Lake, a regional natural recreation asset within the City of Dallas. Areas for dredging were selected based primarily on the goal to restore lake depth for sailing and boating recreation, as well as improve the overall health of the lake. Stakeholder input received at public meetings guided delineations for areas to dredge or exclude, and input from City staff was used to identify other areas of maintenance concern.
The City’s historical approach to sedimentation in White Rock Lake is to dredge the lake every 20-25 years under large capital projects. This dredging approach has historically not been enough to keep up with sedimentation and maintain the lake at the desired minimum depth. Alternatives were developed with the primary goal of restoring the recreational depth and performing dredging at a scale and frequency sufficient to maintain the desired threshold.
At the time of this initial screening, the most likely dredging scenario is a hydraulic dredge operation which pumps slurry material directly to an offsite dewatering and disposal location. The data and techniques developed for this study serve as a decision-making tool to explore implementation scenarios and determine the best use of resources as they apply to a dredging program.
The thoughtful implementation of a dredging program will be critical to maintain White Rock Lake as a valuable recreational destination in the City of Dallas. Public involvement has been a key component of this feasibility study largely contributed to the success of previous dredging operations. The City plans to continue to engage the appropriate stakeholders and evaluate potential funding sources during budget planning to decide on a path forward.
11:15 am – 12:15 pm LUNCH BREAK 12:15 pm – 12:45 pm REMO Networking
10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK E – FLOODPLAIN MANAGEMENT IN 2D 1:00 pm – 1:30 pm E3: What in the world is 1D & 2D? An Intro for FPAs / Policy Makers/ Non- Engineers Speaker: Sarada Kalikivaya, PE, PMP, CFM; Atkins Presentation: One-dimensional (1D) surface water hydraulic models have a long track record. Historically, they have been used to calculate water discharge, elevation, velocity, and many other parameters for engineers to use in many applications. In order to gain a visual understanding, using 1D models is like driving down a one-way street with a speed-limit sign; you can only drive in one direction and at the signed speed limit. But using 2D modeling is a game-changer. The assumptions of a single water surface elevation and flow direction perpendicular to the cross section may be the starkest contrasts between 1D vs 2D models. If we return to our driving example, using a 2D model is like driving the same car around an empty airfield; now you can drive in any direction and at any speed you like!
This presentation will introduce the basic concepts of where, when and how to use 1D and 2D models. Discussion about data requirements, advantages and disadvantages. This presentation is intended for Elected officials, FPAs and all other non-engineers.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK E – FLOODPLAIN MANAGEMENT IN 2D
1:45 pm – 2:15 pm E4: Is This Considered a Rise? Evaluating Impacts with 2D Hydraulic Modeling Speakers: Robert Armstrong, PE, CFM; Huitt-Zollars Lacy Rhoades, EIT; Huitt-Zollars Mayra Rodriguez, EIT; Huitt-Zollars Presentation: Two dimensional (2D) hydraulic modeling can provide a more accurate representation of complex hydraulic situations through an understanding of surface runoff and riverine flooding. With programs like HEC-RAS and other modeling softwares continuing their expansion of 2D modeling capabilities, more private and public entities are opting for a 2D model to complete hydraulic analyses. With a 2D model producing individual results at each grid cell, how do you compare impacts, communicate results, and meet criteria that was developed for 1D modeling?
In this presentation we will discuss alternatives on how to analyze and present 2D hydraulic model results.
2:30 pm – 3:00 pm E5: Harnessing RASController for Floodplain Mitigation Speakers: Jeremy Dixon, PE, CFM; Freese & Nichols David Phan, PE, CFM; City of Dallas Presentation: Impact Analysis for development in and near sump floodplains in the City of Dallas used to require a license for expensive software and a degree of expertise not common among most developers in the City. This inadvertently made the software a barrier to entry and changes the economics of infill development in these areas. Freese and Nichols, Inc. used the RASController functionality of HEC-RAS to simulate tens of thousands of potential developments in the various sumps around the City to determine appropriate configurations of these developments such that they would cause no adverse impact in the sump.
This presentation discusses some of the technical decisions made and demonstrates some of the procedures used to develop this process.
3:15 – 3:45 pm E6: Floodway Development Methodologies for 1D Unsteady And 2D Models Speaker: Sarada Kalikivaya, PE, PMP, CFM; Atkins Presentation: The concept of the FEMA regulatory floodway was established to preserve channel capacity to pass the 100-year flow. It is an effective floodplain management tool used to regulate development along channels to prevent adverse impacts of cumulative water surface elevation increases due to excessive encroachment. Allowable floodway surcharge limits between 0 to 1 foot are adopted and enforced by different states, with allowable surcharge limit of 1 foot in Texas.
Since release of HEC-RAS 5.0 in 2016, 2D models are increasingly used for hydraulic analysis and for streams where effective regulatory floodway is present, an updated floodway analysis will be required. 1D unsteady and 2D modeling is complex and surcharge-based floodway development in unsteady and 2D environments is further complicated by model stability challenges and the highly iterative nature of the development process. Since the unsteady state analysis accounts for the hydrograph volume of floodways, peak flows increase with encroachment and produces wider floodway widths than a steady state analysis. There are at least four different methodologies that can be employed for developing 1D unsteady or 2D floodways.
This presentation will illustrate these methodologies through example models and provide a comparative analysis of different methodologies in terms of their strengths, limitations, and suitability. The goal of this presentation is to enhance the understanding of 1D unsteady and 2D floodway modeling methodologies.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK E – FLOODPLAIN MANAGEMENT IN 2D
4:00 pm – 4:30 pm E7: Kingwood Texas Flood Study- An Opportunity to Align Complex Analysis with Tropical Storm Imelda Speaker: Derek St. John, PE, CFM; Gauge Engineering
Presentation: This study will present the approach and initial findings of the Kingwood Drainage Study while taking a dive into how Tropical Storm Imelda, which occurred mid-study, impacted and influenced the study and results.
10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK F – SCIENCE AND TECHNOLOGY
10:00 am – 10:30 am F1: Framework for Visualizing HEC-RAS Hydraulic Model Output on the Web Speakers: Myles McManus, PE; RPS Group Sean Micek, EIT; RPS Group Luis Partida; RPS Group Presentation: To more easily visualize HEC-RAS results for any user or stakeholder, RPS has created its own web application called RPS- FloodMap. The app brings the results from RAS HDF output files to an interactive, online map, easily viewable on any platform. The results come to life through visualization tools include velocity particle tracing, flood inundation animations by simulation time step, and a gridded mapping of Water Surface Elevation (WSEL) or any hydraulic output values for comparison between different frequency storms and design scenarios.
The framework is built to be extensible in the data provided, such that a client would be able to upload additional model output and have it displayed in the web map, or an automated data pipeline would refresh results in an online-hosted repository every time a model is re-ran. The web map interface can also provide emergency managers the capability to have real-time events disseminated as forecasted flood inundation animations, as well as provide potential ‘What-if’ scenarios such as levee and dam breaches that could occur from forecasted hydrology / meteorology. The framework leverages the RAS Tileserver provided from HEC to create the dataset and using a Hapi webserver.
RPS would like to present the tool to open a dialogue for potential new applications and use-cases HEC-RAS output data. We would like to share the details on what technology was involved in the creation of this framework and how solutions outside of the H&H industry were leveraged in this product. By incorporating technology used in other technical fields, we can develop new ways of improving how we analyze, understand, communicate and interpret hydraulic model results. This application will reduce project latency and allow clients, the public and engineers to work together to come up with better solutions to inundation problems that are becoming ever more complex.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK F – SCIENCE AND TECHNOLOGY
10:45 am – 11:15 am F2: Gauge Data Driven Solutions Speakers: Angela Davidson, PE, CFM; Halff Associates Brian Downing, PE, CFM; Halff Associates Presentation: As hydrologic and hydraulic modeling becomes increasingly complex, more applications will require the use of gauge data while providing more accurate modeling, increased confidence in disaster relief and response. Additional effort will be required to both acquire and analyze the data. Determining the best available data can be a substantial task. Gauge data comes in many forms and from many sources. The gauge data can differ greatly from one source to another.
During the presentation, we will discuss how to obtain common sources of gauge data, how to determine the accuracy of the data, and applications for the gauge data.
11:15 am – 12:15 pm LUNCH BREAK 12:15 pm – 12:45 pm REMO Networking 1:00 pm – 1:30 pm F3: The Flattened Earth – Basic Concepts & Common Problems with Coordinate Systems (Part 1) Speaker: Randy Dueck, PE, CFM; Halff Associates Justin Moore, GIS Analyst; Halff Associates Presentation: Have you ever wondered why we need coordinate systems and what these different coordinate systems mean? As it turns out, coordinate systems are an integral component of meaningful flood risk mapping and flood control projects. They enable us to accurately represent flood zones and impacted surface features on a 2-dimensional plane. Modern CAD and GIS tools have made the visualization environment convenient and seemingly straight-forward. However, this convenience may result in a lack of awareness and competency with regards to spatial inaccuracies, their implications, and their resolutions. Hence, there is an acute need for technical staff to develop an understanding of the underlying principles comprising geographic and projected coordinate systems.
This presentation attempts to address that need by sparking a renewed interest in the subject. Fresh visuals and live demonstrations will be used to present the basic concepts of projecting surface features on the curved surface of the earth onto flat planes. Basic topics covered will include geographic coordinate systems, projections, geoids, ellipsoids, and datums. These basic topics will be reinforced by identifying each of them in the context of the Texas State Plane FIPS 4202 coordinate system. Common scenarios of spatial misalignments in data, measurement inaccuracies, diagnosis of problems, and potential resolutions will be presented in the context of real projects and watersheds in Texas.
1:45 pm – 2:15 pm F4: The Flattened Earth – Basic Concepts & Common Problems with Coordinate Systems (Part 2) Speaker: Randy Dueck, PE, CFM; Halff Associates Justin Moore, GIS Analyst; Halff Associates Presentation: PART 2
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK F – SCIENCE AND TECHNOLOGY
2:30 pm – 3:00 pm F5: The Best Available Science: A Roadmap to Future Conditions Flood Hazard Mapping Speakers: Sarada Kalikivaya, PE, PMP, CFM; Atkins Presentation: Earth’s climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities. The impacts of global climate change are already happening in the United States and are projected to continue intensifying. Sea levels along the coastlines are rising at inconsistent rates—higher rates along the Gulf of Mexico coastline where land is sinking. Precipitation is also changing, with increases in the Northeast, Midwest, and Great Plains and decreases in the Southwest and Southeast. Examining future conditions means looking at how changing drivers over time will have an impact on risks to communities. Changes to land development, weather patterns, and sea levels may result in a community having a greater risk of flooding in the future.
Congress has recognized the impacts of climate change on the National Flood Insurance Program (NFIP). The Biggert-Waters Flood Insurance Reform Act of 2012 established of the Technical Mapping Advisory Council to provide specific recommendations to FEMA to ensure that the Flood Insurance Rate Maps continue to incorporate the best available climate science to assess flood risks and that FEMA uses the best available methodology to consider the impact of sea level rise and future development on flood risks.
Where future conditions present both increasing and decreasing changes, future-conditions flood hazard and risk identification are challenging and requires an understanding of many influencing drivers and any combination of those drivers. State, local, tribal, and territorial (SLTT) governments can take steps to implement flood hazard mapping activities that incorporate different changing drivers over time that are applicable to them. The presentation will focus on 5 drivers (Land Use, Precipitation, Sea Level Rise, Coastal Erosion, and Riverine Erosion) and highlight their existing and evolving methodologies and case studies by federal, state, local government, academia and non-profit organizations.
END OF TRACK F
Thank you to our Riverbed Sponsors
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK G – EROSION\STREAM RESTORATION
10:00 am – 10:30 am G1: Harvey Recovery Project – Buffalo Bayou Speaker: David Coryn, PE, CFM; Jones & Carter Zhi Gao Lee, PE, CFM; Jones & Carter Presentation: As a result of the historical flooding that has occurred in the Houston area in 2015, 2016, and 2017, major erosion has occurred along rivers, channels, creeks and bayous throughout the Houston area. From damaged outfalls to major slope failures, Hydrology and Hydraulics engineers in Texas have been tasked with not only repairing these areas but applying solutions that may prevent similar issues in the future.
As part of the post Hurricane Harvey disaster recovery project, J|C was tasked with channel improvements along Buffalo Bayou from Sabine St. to Shepherd Dr., J|C’s objectives included removing sediment, stabilizing slope failures along the bayou and install preventative measures to stop future erosion occurring. JC designed improvements to pedestrian and biking trails near areas of erosion through coordination with the Buffalo Bayou Partnership. In all J|C coordinated with Harris County Flood Control, City of Houston, and Buffalo Bayou Partnership.
In addition to the design, the construction required detailed methods for the installation of the rip rap below water, proposed rip rap buttress design. As well as meeting the requirement set forth by the public within the park.
Objectives To Be Covered: • Overview of the erosion along the bayou. • Outline the design constraints within the area, including the existing conditions, water surface elevations, and park constraints • Discussion of design concepts for erosion protection and velocity mitigation. • Highlight the key steps and complications of the construction.
10:45 am – 11:15 am G2: Oyster Creek Desnagging Project Speakers: Clay Forister, PE, CFM; Brazoria County Presentation: In 2016, Brazoria County experienced major flooding due to Hurricane Harvey and received over $15M in disaster relief funds. The County elected to apply a portion of these funds toward “desnagging” 49 miles of Oyster Creek and Bastrop Bayou by removing vegetative and flood-related debris via barge-mounted operations. This minimally invasive approach avoided expensive and lengthy environmental review and approval and resulted in the restoration of these watersheds to natural hydraulic conditions with an immediate reduction in flood risk.
11:15 am – 12:15 pm LUNCH BREAK 12:15 pm – 12:45 pm REMO Networking
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK G – EROSION\STREAM RESTORATION
1:00 pm – 1:30 pm G3: Holland Channel: Addressing Erosion Mitigation, Flood Protection and Floodplain Ownership in a Developing Watershed Speaker: Keith Byrne, PE, CFM; Freese & Nichols Chad Marbut, PE, CFM; City of Weatherford Presentation: The City of Weatherford developed a watershed masterplan for Holland Lake Creek in 2013. The watershed study identified a variety of capital projects to address flooding and erosion risks throughout the watershed. The City has recently completed the majority of the critical projects including the Holland Lake Channel Improvements project which included a robust preservation plan to protect the floodplain and greenbelt as part of the overall stormwater utility purpose. Holland Channel was eroding and threatening homes and sending sediment downstream to Holland Lake, an important cultural element in the City’s most prominent park.
The channel was also flooding private property and creating a safety hazard. In the Timber Creek neighborhood, the lots were platted across the creek and the City had no property rights to make improvements to the creek. The City addressed all three issues with a single project which included property acquisition, a modular block retaining wall to remove the floodplain from the remaining private property, and constructing natural rock drop structures to stabilize the erosion in the creek. This presentation will give an overview of this multi-faceted, complex project.
1:45 pm – 2:15 pm G4: Mission Reach- Lone Star Site Erosion Toewood for Bank Stabilization Speakers: Tami Norton, PE, CFM, PMP, ENV SP; Ecosystem Planning & Restoration Collen J. Brownlow, PE, CFM; San Antonio River Authority Presentation: The San Antonio River, along the River Walk Mission Reach Trail System, was experiencing bank erosion near Roosevelt Park. The San Antonio River Authority (SARA) desired to address the erosion using natural channel design techniques, evaluating alternatives to avoid hard armoring methods, to preserve the natural look of the river and provide fish habitat, while protecting the riverbank.
The recently constructed Lone Star Bank Stabilization Project, completed in August 2020, will be presented, and include discussion of project goals and the selection of natural channel design techniques, specifically toewood, to address the erosion. Additionally, project constraints and challenges with the design, permitting, construction, and maintenance will be presented.
2:30 pm – 3:00 pm G5: A Case Study: Restoring Streams in Sandy Soil Conditions Speakers: Rebecca Stubbs, PE; McAdams
Presentation: An Unnamed Tributary (UT) to the Cape Fear River on the Methodist University’s campus, in Fayetteville, NC drains 227 acres of urban watershed. The University in combination with grant funding restored 2,200 linear feet and preserved an additional 771 linear feet of on-site stream channel. Fayetteville is considered inner coastal plain in North Carolina and is generally characterized by sandy soils combined with rolling topography.
The existing channel was severely incised resulting from active bank erosion creating a small canyon like feel in places. A Priority Two approach was used to create a floodplain bench within the steep sandy side slopes and connect the proposed stream channel to a regularly accessible floodplain. During construction, site conditions proved to be especially challenging and modifications to the approved design were required to address runoff from the surrounding developed campus in addition to modifications in channel dimension to prevent bank washouts prior to vegetation establishment. As the University considers restoring the contiguous upper section, lessons learned during construction will inform the design approach of Phase 2.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK G – EROSION\STREAM RESTORATION
3:15 – 3:45 pm G6: Water and Soil – Geotechnical Considerations for HCFCD Channel Erosion Repairs Speakers: Yu-Chun Su, Ph.D., P.E., CFM, CPESC, CPSWQ; Lockwood, Andrews & Newnam, Inc Ron Langston, PE; Cibor Geoconsultants B. Krishna “Kris” Goparaju, PhD, PE; Cibor Geoconsultants Joseph Cibor, PE, D.GE; Cibor Geoconsultants Julius Serrano, PE; Lockwood, Andrews & Newnam, Inc. Presentation: Lockwood Andrews & Newnam, Inc. (LAN) and its subconsultants has supported Harris County Flood Control District (HCFCD) in the design and construction of erosion repairs of several HCFCD channel reaches, including P135-00-00, G103-53-00, P121-01-00, P130-05-00, P130-09-00, and P118-03-00. The purpose of the project is to restore the channels to their original design capacities and address any erosion and siltation issues along the channels. Many of these projects encountered geotechnical issues such as dispersive soils, steep channel side slopes, rapid drawdown, etc. that required substantial geotechnical considerations and discussion in the channel repair designs.
One specific geotechnical consideration is over the use of geotextiles below riprap on channel side slopes. Over the years, HCFCD has seen slippage of riprap where geotextiles have been used beneath riprap placed over clays but slippage of riprap has not been observed where geotextiles have been used beneath riprap placed over sands. For this reason, a consensus at the HCFCD has been to only use geotextiles beneath riprap placed over sands. Some reasons for not using geotextiles beneath riprap placed over clays in Harris County have to do with (1) the overall purpose of using the geotextiles in combination with the differences in the properties of Harris County clays and sands, (2) the drainage features of clays versus sands, and (3) the shrink-swell characteristics of clays versus sands.
While the US Fabrics “Riprap Geotextile Installation Guide”, Section 3.0 recommends using a nonwoven geotextile for the placement of riprap over clays, the June 2020 HCFCD “2020 Standard Construction Specifications and Details,” Section 02379, Paragraph 2.1, A. does not allow the use of nonwoven geotextiles on HCFCD projects. This presentation will cover the geotechnical challenges encountered and lessons learned from these channel erosion repairs design project.
4:00 pm – 4:30 pm G7: Talk Dirty to Me: Understanding Soils for Floodplain Management and Watershed Planning Speaker: Matthew Berg, PhD; Simfero Consultants Kieran Sikdar, CFM; West Consultants Presentation: Understandably, water usually gets the attention in discussions of flood planning and mitigation. But if that’s where we leave it, we miss out on understanding one of the biggest factors in floodplain management – and a chance to increase our likelihood of success. Patterns of flood risk and recent high-profile events have made it clear that soils are among the most important contributors to and consequences of flooding. Processes of infiltration, erosion, and sedimentation play an outsized role in determining flood behavior and how watersheds function overall. Yet a number of traditional management strategies can exacerbate soil and sediment issues, and vice versa. So how do we handle these challenges in tension with one another?
We’ll look at some of the physical properties of soils that can make or break watershed management efforts and learn methods to identify potential critical areas deserving your attention. We’ll also discuss biological aspects of soils and introduce emerging cost-effective strategies for restoring their function to boost floodplain management. If done right, these approaches can help local sponsors avoid costly efforts to undo damage after it happens. As a result of this process-based presentation, attendees will able to more effectively incorporate soil considerations into watershed management efforts, with multiple benefits far beyond flood mitigation. Your drinking water supplies, local property values, community recreation opportunities, and regional ecosystems will thank you.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK H – STATE\REGIONAL FLOOD PLANNING
10:00 am – 10:30 am H1: Regional Flood Planning and Regional Water Planning – Same Difference? Speakers: Stephanie Griffin, PE, CFM; Halff Associates Scott Hubley, PE, CFM; Freese & Nichols Presentation: The presentation will compare the Senate Bill 1 (SB1) legislation that authorized the State Water Plan and Senate Bill 8 (SB8) legislation that authorized the State Flood Plan, as well as the history of droughts and floods that spurred the legislation. The benefits of local buy- in using a bottom up water planning approach have resulted in project implementation at the local level. Similar benefits are anticipated with the regional flood planning process.
In 1997, the Texas Legislature passed SB1 that created the regional water planning and state water planning processes. This legislation was the first of its kind to develop a 50-year water supply plan from the bottom up. The ongoing process of developing/updating regional water plans and rolling them into a state water plan every five years continues today.
Fast forward some 20+ years. The Texas Legislature passed SB8 in 2019 to establish the regional flood and state flood planning processes similar to the water planning processes. The processes are similar in nature, the differences between water supply planning and flood mitigation planning are significant. Therefore, the regional and state flood plans will be unique in their own right.
10:45 am – 11:15 am H2: How To Be Successful in the Regional Flood Planning Process Speakers: Allison Wood, PE, CFM; Huitt-Zollars Robert Armstrong, PE, CFM; Huitt-Zollars Matt Hiland, PMP Presentation: With SB7, SB8, and Prop 8 passed in 2019, Texas law requires the preparation of 15 regional flood plans by 1/10/2023 and a Comprehensive State Flood Plan by 9/1/2024. Successful completion will require enormous effort from entities across the state. Success will also depend on an unprecedented level of information management, communication, coordination, outreach, feedback, and alternatives analysis among State, Federal, and Local government agencies, businesses, and citizens.
In this presentation we will present some ideas to help demystify the flood planning process and to help local stakeholders understand the role they can play in this process to achieve success. We will also discuss practical steps that can be taken to prepare your local flood data to be included in the regional plan and how to prepare projects to be prioritized in the state flood plan.
11:15 am – 12:15 pm LUNCH BREAK 12:15 pm – 12:45 pm REMO Networking
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK H – STATE\REGIONAL FLOOD PLANNING 1:00 pm – 1:30 pm H3: Structure Survey – There’s an App for That! Speaker: Rebecca Katzke, PE, PMP, CFM, ENV SP; Atkins Brett Sachtleben, PE, CFM; Atkins Presentation: HCFCD partnered with Atkins, LAN, and Torres & Associates to conduct a level of service analysis of all HCFCD-owned channels (2503 river miles) within Harris County. As part of this analysis, Atkins’ rapid flood delineator (RFD) tool was used to develop 1D hydraulic models for 1212 miles of unstudied streams including over 2500 crossings. Field survey was performed on 1200 structures for inclusion in the new hydraulic models.
How do you obtain structure survey in a cost and time efficient manner? A survey collector app, compatible with both Android and iPhone, was developed to streamline and standardize capture of various measurements for bridge and culvert crossings. The application integrates with ArcGIS Online servers to provide real-time updates of data collected in the field. Data collected can be easily exported to HEC-RAS to reduce manual data entry. The procedure allowed numerous crews to work concurrently and simplified data collection.
Topics covered in this presentation include: • Data capture standard development • Application demonstration • Data entry simplification • HEC-RAS integration
1:45 pm – 2:15 pm H4: Watershed Wide Floodplain Remapping – A Balance of Model Advancement & Practicality Speakers: Rebecca Katzke, PE, PMP, CFM, ENV SP; Atkins Brandon Hilbrich, PE, CFM; HDR Engineering Presentation: As the FEMA Delegate, the San Antonio River Authority (SARA) is updating floodplain mapping for the major watersheds in Bexar County. These updates have been initiated to account for increased rainfall depths from NOAA Atlas 14, recently acquired new LiDAR topography, updated land use data, and impacts of karst terrain. This large scale floodplain remapping effort presented an opportunity for SARA to update data resources, H&H models, modeling standards, and more accurate mapping products for the area.
The Atkins/HDR team was assigned the Salado Creek Watershed located in the southeastern section of the Greater San Antonio metropolitan area. During the 2010 DFIRM Map Modernization effort, approximately 265 miles of effective streams were studied and mapped. As part of the remapping effort, the total number of stream miles were updated but also increased the detailed studied streams from approximately 163 miles to 181 miles and include 48 miles of limited detail streams and 35.5 miles of approximate studied streams. This presentation will discuss the overall implementation of watershed-wide H&H and floodplain updates and take a dive into the details of the Hydraulic updates including:
• Physical changes to watershed over the last decade • Evaluate modeling capabilities and methodologies (Standard Updates) • Brief overview of Hydrology Changes • Discuss modeling approach * Data Resources, * 1D or 2D computation, * User Friendly • Remapping Results • Challenges from a watershed-wide update to local unique characteristics.
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10:00 am – 4:30 pm CONCURRENT SESSIONS TRACK H – FEMA
2:30 pm – 3:00 pm H5: Adapting Flood Risk Open Houses to a Virtual World – A Case Study with El Paso, Texas Speakers: Bruce Bender, CFM; Bender Consulting Service, Inc. Diane Howe, CFM; FEMA, Region 6
Presentation: El Paso County countywide preliminary flood maps were released last summer just as Covid-19 was starting to peak. The current flood maps were based on data back from the 1980’s and 90’s and the new ones showed 11,000 properties being added to and 15,000 properties being removed from the floodplain due to levee accreditation results. In-person meetings would not be an option for quite a while, so the county and the city chose not to delay the outreach as their citizens needed to know their updated flood risk. The challenge now was how best to reach out to property owners in this very populated bilingual border county to educate them about how their flood risk may be changing and options that they had.
This session will describe how coordinating with multiple partners helped create and implement a multi-prong outreach approach that accommodated this new virtual need. The effort resulted in posting local bilingual webpages and videos representing different stations at a Flood Risk Open House, providing bilingual material ranging from social media to postcards to fact sheets, and hosting three 90-minute live online Open Houses with Q&A sessions and American Sign Language interpretation. Come hear lessons learned and walk away with ideas for future virtual public meetings you may be involved with.
3:15 – 3:45 pm H6: Flood Myths vs Facts – A Video Series Speaker: Rebecca Dake, CFM; FEMA Region 6 Gilbert Giron, CFM; FEMA Region 6 Presentation: FEMA’s Gilbert Giron and Rebecca Dake will present seven different flood myth and facts. Participants will view short videos that address each misunderstanding or misinformation. Hear more about the content and how you can share the video series with your stakeholders. We want to hear your feedback for future video projects and get your FEMA flood insurance questions answered. Click here to view one of the videos.
4:00 pm – 4:30 pm H7: Substantial Damage Under the NFIP Speaker: Brian Bartley, CFM; FEMA Region 6 Presentation: Overview of: The Ideal State of Disaster Readiness for Substantial Damage Administration Response. Overview presentation of the elements needed to prepare your community to meet the miniumum National Flood Insurance Program (NFIP) requirements of substantial damage determinations and administratin in the wake of a disaster. This would be an overview presentation offering the attendee an awareness of the subject and resources to investigate and learn more.
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Make sure and thank all of our sponsors by visiting them in the REMO Networking Rooms. Its their support that make these events happen.
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