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Published in final edited form as: J Plan Educ Res. 2023 Oct 9;45(2):318–329. doi: 10.1177/0739456X231198061

Design for Storm Surge Flooding Adaptation: Facilitating Emergency Evacuation with Adaptive Landscape Form-Based Codes

Hope Hui Rising a, Galen Newman a
PMCID: PMC12327813  NIHMSID: NIHMS1957317  PMID: 40771431

Abstract

Lack of consensus and funding led to a focus on building retrofits after storm surge flooding and collective inaction for undertaking cross-jurisdictional adaptation pathways planning. Using Seabrook, TX, United States, as a test case, this paper demonstrates the feasibility of using design games (participatory community visioning and design processes) to develop consensus-based, performance-driven, form-based codes from an adaptive landscape framework to facilitate emergency evacuation during storm surge flooding. The framework provides bottom-up mechanisms to enhance the sizes, coverages, quantities, and connectivity of multi-scalar engineered structural and nature-based solutions as a complex adaptive system to increase evacuation time and decrease flood-prone population.

Keywords: landscape performance, adaptation pathways planning, engineered structural solutions, nature-based solutions

Introduction

Form-Based Codes for District-Level Flood Adaptation

Coastal cities have become more vulnerable to storm surge flooding due to sea level rise (SLR) (De Dominicis et al. 2020). However, even with buyout assistance, managed retreat remains less popular than in-situ flood adaptation (Braamskamp and Penning-Rowsell 2018). To facilitate in-situ flood adaptation, most communities have focused on capacity building rather than the use of conventional zoning codes (Stults and Woodruff 2017) because it is costly and time-consuming to recode an entire city. Form-based codes, on the other hand, have been used for district-level flood adaptation in Hazard Transect Overlay Districts (H-Transects) (Faga 2014; Smith, Anderson, and Perkes 2021; Talen 2009) for communities without conventional zoning. Other communities can also facilitate in-situ flood adaptation by integrating form-based codes with conventional zoning to avoid the complicated process of rezoning (Faga 2014). However, the adoption of form-based codes has been slower than anticipated by the Form-Based Code Institute (FBCI) because regulating design with form-based codes entails a steep learning curve for complicated rules (Faga 2014). To address this challenge, FBCI (2021) created a process of using engagement workshops to develop a place-based community vision as a driver for generating consensus-based form-based codes for more rapid public adoption. This FBCI process inspires the proposed consensus-based adaptive landscape framework for facilitating storm surge flood adaptation.

Validating Performance-Driven, Form-Based Codes as Regulatory Tools with Public Acceptance

Form-based flood adaptation (Watson 2019) has been facilitated by optimizing design prototypes (or sectional perspectives of generic design concepts with forms and materiality) (Rising 2017) with flood simulations (Simonovic and Peck 2013; Yin, Lin, and Yu 2016) and landscape performance calculators (Kumar et al. 2021; Newman et al. 2020; Newman et al. 2022). Among these functionally optimized prototypes, those identified as the most publicly acceptable for specific H-Transects (Han 2021) during engagement workshops become form-based codes with regulatory power for safeguarding a consensus-based community vision (FBCI 2021; Moule, Dittmar, and Polyzoides 2008; Talen 2009).

As sea level rises, even with in-situ flood adaptation, the H-Transects will become more prone to storm surge flooding (De Dominicis et al. 2020) to ultimately necessitate more effective emergency evacuation. However, physical alterations after storm surge flooding have not focused on improving emergency evacuation. Rather, they have primarily involved elevating buildings (Lin and Shullman 2017; Masoomi et al. 2019) with silts even though building on silts can be damaged by even a 1.5-ft storm surge (Coulbourne 2013). In addition, building-based interventions are not as effective in reducing flood water flows and levels as physical interventions in the landscape (Maragno et al. 2018; Maxwell et al. 2021). To delay storm surge impacts and provide evacuees more time and means to reach safe destinations, there is a need to mainstream flood-adaptive prototypes in the landscape as form-based codes within H-Transects.

Toward an Adaptive Landscape Framework for Emergency Evacuation

Engineered structural solutions (ESSs) and/or nature-based solutions (NBSs) have been proposed in front of high-water marks (Smolders et al. 2020) to enable in-situ flood adaptation. Raising the shorelines with ESSs can increase riverine and pluvial flooding due to “bathtub effects,” or entrapment of rainfall-induced runoffs behind ESSs (Rising 2017); In contrast, NBSs, such as coastal wetlands, can capture and infiltrate runoffs in addition to attenuating waves and storm surges (Debele et al. 2019) with minimal “bathtub effects.” While ESSs at high-water marks can cause habitat squeeze (or habitat loss in the intertidal habitat zone) (Leo et al. 2019), NBSs migrate with habitats as SLR shifts low-water marks landwards (Bilkovic et al. 2016).

An increasing number of jurisdictions mandated a rolling easement to keep the area between the high- and low-water marks open to public access (Leo et al. 2019). As the easement shifts inland with SLR, more NBSs in front of the original low-water marks will be inundated. Meanwhile, more ESSs (located at and right behind the original high-water marks) and coastal residences will have to confront “takings,” which refer to the government’s actions to seize private properties to increase public welfare (Jungreis 2018).

Smaller-scale NBSs, such as green streets and rain gardens, have been used to mitigate street flooding although they are less effective than smaller-scale ESSs, including floodable streets and plazas, in coastal areas with high groundwater tables (Dai, Wörner, and van Rijswick 2018; Fournier et al. 2016; Sörensen et al. 2016). These smaller-scale interventions in the landscape behind high-water marks are less costly and time-consuming to implement, less prone to SLR-induced inundation, and less likely to encounter takings than large-scale interventions at or in front of high-water marks. Yet, these smaller-scale landscape interventions behind high-water marks have not been considered for storm surge adaptation.

When inundated by SLR, smaller-scale ESSs and NBSs behind the original high-water marks can potentially be as effective collectively as large-scale NBSs in front of the original high-water marks, such as wetlands, mangroves, and/or oyster reefs (Dasgupta et al. 2019; Hopkinson 2020; Möller et al. 2014; Narayan et al. 2017; Temmerman et al. 2013; Wiberg et al. 2019) through (1) providing depressions and friction-generating features to reduce flood water flows and levels and (2) forming a shallow water area to attenuate wave and storm surges. Despite the lack of awareness of smaller-scale landscape interventions as more accessible solutions, lack of consensus has been the main cause of inaction for storm surge adaptation (Dannenberg et al. 2019; González-Riancho, Gerkensmeier, and Ratter 2017). There is a need to explore the potential of using a consensus-based adaptive landscape framework to generate form-based codes from multi-scalar ESSs and NBSs to facilitate more effective emergency evacuation during storm surge flooding.

Research Design

Research Goal

This test case explored the potential of a consensus-based adaptive landscape framework in facilitating emergency evacuation during storm surge flooding within the context of Seabrook, TX, United States.

Proposed Consensus-Based Adaptive Landscape Framework

The proposed framework identifies form-based codes from multi-scalar ESS and NBS prototypes using a five-step framework and involves (1) identifying factors underlying flood vulnerability and emergency evacuation effectiveness through literature review and interviews; (2) benchmarking worse-case flooding scenarios through literature review, interviews, and analysis of geographic information; (3) generating hypotheses of form-based codes from functionally optimized prototypes through comparative precedent studies and performance evaluation; (4) distilling form-based codes from publicly acceptable adaptive landscape prototypes through design games, which are consensus-based participatory design processes inspired to facilitate the adoption of form-based codes; and (5) evaluating form-based codes for emergency evacuation using SLR scenario-specific social performance indicators, such as the number of flood-vulnerable population and evacuation time.

Framing Form-Based Codes as Components of a Complex Adaptive System

To model the impact of form-based SLR adaptation strategies, a gridded urban layout with a flat topography has been used to measure the wave force on the components (buildings) at the system (street and block) level (Wang 2014). While this top-down approach measures the component-level performance of system-level interventions, it is not feasible in Texas with minimal zoning to regulate development patterns. Given the uncertainties in climate science, SLR projections from varying sources have failed to help determine a location-specific sea level for adaptation pathways planning (Haasnoot et al. 2019; Lemos and Rood 2010). There are still tremendous uncertainties and spatiotemporal variations in the predictions of hurricane-induced storm tide (surge + tide) (Kowaleski et al. 2020). As a result, the test case conceptualizes landscape as a complex adaptive system that self-organizes to adapt to changing external conditions (such as flood levels without target timeframes) with system (city)-level performances (such as evacuation time) as emergent properties of component (site)-level interventions (such as multi-scalar adaptive landscape components) and their connections (Kim and Mackey 2014).

Test Case

Site Selection

Texas is the first state that mandated a rolling easement between low- and high-water marks known as the Texas Open Beaches Act (McLaughlin 2011). The rolling easement has gained traction in other states as an SLR adaptation tool for facilitating managed retreat (Dyckman, St. John, and London 2014; Kousky 2014). The area around Galveston Bay in Texas provided appropriate contextual framing because (1) most of its surrounding Houston-Galveston-Brazoria Consolidated Metropolitan Statistical Area (CMSA) has been fast growing with minimal development regulations in flood-prone areas; (2) Harris County (the home of Houston), the most populated in the CMSA, has the most socially vulnerable households in the region that require effective emergency evacuation to circumvent the impacts of flood-induced explosions at refineries and chemical plants (Malecha et al. 2020); and (3) Seabrook, located within the Harris County’s storm surge impact zone, is likely to be more receptive to form-based codes than other bayfront municipalities because it has some, despite limited, zoning codes (Kuehnel 1987).

Identifying Factors Influencing Flood Vulnerability and Emergency Evacuation Effectiveness

Seabrook is primarily at the southeastern corner of Harris County, with a few of its water surfaces in Chamber County. The city borders Clear Lake to the south, Taylor Lake to the northwest, and Galveston Bay to the east. Clear Lake receives runoffs from Clear Creek, Armand Bayou, Horsepen Bayou, and Cow Bayou. There is also a new drainage outlet from Clear Lake to Galveston Bay borders, the southeast corner of Seabrook. Seabrook’s location at the mouth of Clear Lake and within the tidal zone makes the city prone to many compounded effects of hurricane-induced storm surge flooding, riverine flooding, and pluvial flooding from precipitation.

The majority of Seabrook’s land cover, historically, was characterized by wetlands, which are critical for draining runoff from inland areas. There are, currently, no shoreline protection mechanisms or wetland conservation policies for Seabrook. Coupled with a lack of land use regulations, developments have gradually replaced wetlands in flood-prone areas (Laible 2003). Home buyers from out of town often purchase units near waterfronts without knowing the flood risks associated with these units. There were flood warning signs showing the flood water levels for category 4 and 5 hurricanes in the Clear Lake Creek area; these signs were removed because of their potentially negative impacts on real estate sales (Blackburn 2018).

In 2005, most of the residents from the CMSA around Galveston Bay were stuck in gridlocked traffic when they attempted to evacuate for Hurricane Rita. Rita led to the largest emergency evacuation in U.S. history. Initially, a category 5 hurricane, Rita luckily weakened before it made landfall but still resulted in 120 deaths, many of which took place during emergency evacuation (Knabb, Brown, and Rhome 2006; Zachria and Patel 2006). The death toll associated with the emergency evacuation during Rita made the public perceive emergency evacuation as less safe than shelter-in-place (Newman et al. 2016).

In September of 2008, Hurricane Ike made landfall near Galveston as a category 2 hurricane. Its large-size wind field was similar to that of a category 5 hurricane, resulting in 10 to 20 ft of storm surge for the Gulf Coast and 214 fatalities (Hlavaty 2018). The National Weather Service issued a series of warnings to help convince residents to evacuate before Hurricane Ike landed. However, many chose to shelter in place because Ike’s classification as a category 2 hurricane suggested a much lower level of risk than Rita did (Morss and Hayden 2010).

Hurricane Ike revealed the importance of facilitating last-minute timely evacuation particularly since storm surge flooding during Ike was significantly more severe than the actual hurricane classification (which is based on wind speed). In this case, adequate time for emergency evacuation can be a matter of life or death. According to interviews conducted by Morss and Hayden (2010), due to Ike’s uncertain track, evacuation orders were not issued until forty-eight hours before the hurricane made landfall, about twenty-four to thirty-six hours before flooding. Emergency evacuation is extremely difficult when attempted the day prior to a hurricane making landfall because many coastal areas are already flooded. Most residents did not fully understand the flood risks posed by Ike until they saw the rising water levels along the coast. Consequently, many ended up getting caught in traffic or stuck on flooded roads, severely delaying or inhibiting their evacuation.

Benchmarking Worst-Case Flooding Scenarios

The storm surge from Hurricane Ike resulted in 10 to 15 ft of flood water in Seabrook (Figure 1A), incapacitating nearly the entire city for a couple of months even with assistance from the Federal Emergency Management Agency. A majority of the homes and businesses between State Highway 146 and Galveston Bay were severely impacted by storm surge flooding during Ike. Storm surge flooding washed away a multitude of homes or gutted their entire bottom floors, mostly along Todville Road paralleling Galveston Bay. Just north of the Kemah Bridge, State Highway 146 was completely inundated and covered by boats and other debris after the waters subsided. While the Seabrook Waterfront district sustained substantial damage, the surge also pushed boats further inland and destroyed boat docks and businesses along Nasa Road 1 back to the Nassau Bay Hilton hotel about 5.6 km from the western edge of Galveston Bay (Sherman and Arrillaga 2008). To facilitate safer and timelier evacuation, it is important to buffer the area east of State Highway 146 from the direct impacts of storm surge.

Figure 1.

Figure 1.

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Hurricane-induced storm surge and pluvial flood levels in Seabrook: Houston-Galveston-Brazoria consolidated metropolitan statistical area storm surge flood levels (A) and pluvial flood levels (B) during Hurricane Ike and storm surge flood levels in and around Seabrook (C).

Source: Harris County Flood Control District, Severe Storm Prediction, Education, and Evacuation from Disasters Center, Andrew Sikes, and Alfrin Islam, June 2021.

Precipitation from Hurricane Harvey, in 2017, resulted in 4.5 to 13 ft of water along waterways near Seabrook. More than 69 linear feet of water level was found along the waterways elsewhere during Harvey (Figure 1B). Hurricane Harvey was a category 4 storm that resulted in a “1,000-year” flood for 4 days, producing more than 40 inches of rain that led to at least 88 deaths. Harvey was primarily a rain-induced pluvial flooding event, without much storm surge flooding. In 2008, to respond to the devastating effects of Ike, the City of Seabrook (2020) required new and substantially improved structures to be constructed above the federal 100-year Base Flood Elevation by 1 ft. The standard was raised from 1 to 1.5 ft in 2016 just before Hurricane Harvey wreaked havoc in 2017. As a result, Seabrook was less devastated than its neighboring jurisdictions during Harvey. Seabrook, however, will become more flood-prone as a rising sea level continues to amplify storm surge flooding, and storms with increasing magnitudes and durations result in more severe pluvial flooding. Despite its increasing flood risks, the city has continued to rebuild and develop in more flood-prone areas by raising building elevations. However, raising building elevations continuously over time can become cost-prohibitive for owners and municipalities (Harte 2017).

Generating Hypotheses of Form-Based Codes from Functionally Optimized Prototypes

As storm surges enter Galveston Bay, the bay’s shallow grounds and morphology constrict water flows to increase water levels drastically (Salas-Monreal, Anis, and Salas-de-Leon 2018). A first-line-of-defense prototype outside of Galveston Bay helps prevent storm surges from amplifying the water levels inside of the Bay (Jonkman and van Berchum 2022). In 2018, the United States Army Corps of Engineers (USACE) and the Texas General Land Office selected such an outer-bay storm surge barrier system as the preferred alternative for protecting the entire Texas coastline from future storm surges (Powell 2018). The plan involves elevating main thoroughfares on Galveston and Bolivar Peninsula to create a continuous seawall along with 71 miles of levees and gates. At first, the system was largely inspired by Texas A&M University at Galveston’s Ike Dike Plan composed of primarily ESSs throughout its entire coastal defense line (Merrell et al. 2010).

There are a number of uncertainties around the implementation of the proposed Ike Dike. Environmental groups have argued for proactive relocation from the flood-prone coastal area in lieu of enabling coastal developments with the outer-bay system (Powell 2018). Many researchers have pointed out the potential impacts this outer-bay system could have on the hydrodynamics, sediment budget, water quality, salinity level, habitat distribution, and morphology in Galveston Bay (Adey 2013; Ruijs 2011). In 2019, USACE replaced the raised roads with a dune system that is less disruptive to the exchange of water across the outer-bay system to address concerns from environmentalists. The revised linear storm surge barrier system down Galveston Island, referred to as the Coastal Spine, hybridized ESSs, such as dikes and sea gates, with NBSs, including beaches, dunes, and habitats (Newman et al. 2016; Powell 2018). However, certain fixed components from this revised system can encounter legal challenges as the sea level rises to push the rolling easement further inland. According to the Texas Open Beaches Act, no one is allowed to erect barriers to prevent the public from using the land within the rolling easement. In addition, the state law prohibits the use of public money to benefit private properties. Consequently, the Texas General Land Commissioner canceled a $40 million beach renourishment project (McLaughlin 2011).

Despite its $31 billion price tag, the outer-bay system was selected over much less costly mid-bay and inner-bay alternatives that can be implemented more quickly to provide the second line of coastal defense without triggering potential legal battles with the Texas Open Beaches Act (Figure 2A) (Collier 2019).

Figure 2.

Figure 2.

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Storm surge protection system alternatives for Galveston Bay, Texas: main components of Galveston Bay Park Plan (A) and multi-prong storm surge protection system (B).

Source: Severe Storm Prediction, Education, and Evacuation from Disasters Center and Alfrin Islam, June 2021.

The Severe Storm Prediction, Education, and Evacuation from Disasters (SSPEED) Center at Rice University and Rogers Partners proposed the Houston-Galveston Area Protection System (H-GAPS) to protect Galveston Bay from storm surges. H-GAPS is composed of (1) mid-bay barrier islands, known as the Galveston Bay Park Plan (GBPP); (2) lower bay gates; and (3) a large storm surge gate similar to the one for the Coastal Spine. The barrier islands were proposed to be between 20 and 24 ft in height and forecasted to reduce the storm surge for western and northern Galveston Bay by 15 to 27.5 ft (Torres et al. 2017) (Figure 3). From the Houston Ship Channel’s existing dredge materials, the barrier islands were to be built along the channel behind a 25-ft-tall levee punctuated by small gates for boats to pass through. The H-GAPS gate was designed to close only during large storms by connecting the barrier islands west and east of the shipping channel.

Figure 3.

Figure 3.

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Storm surge simulation with or without Houston-Galveston area protection system.

Source: Severe Storm Prediction, Education, and Evacuation from Disasters Center and Alfrin Islam, June 2021.

The mid-bay barrier islands function as oyster, fish, and bird habitats, as well as parkland for human enjoyment. Each component provides ecological, recreational, and aesthetic co-benefits to communities, making GBPP a no-regret strategy in the event the outer-bay system has been put in place. In addition, closing Galveston Bay temporarily with the outer-bay prototype could result in a higher water level in the Bay due to trapping runoffs from (1) various waterways, such as the Trinity River, that otherwise would have discharged into the Gulf through the Bay; and (2) extreme precipitation events: During Hurricane Harvey in 2017, long-lasting elevated water level was observed in the Bay and confirmed by hydrodynamic modeling (Du et al. 2019). Only two years from the first 1,000-year flood caused by Hurricane Harvey, tropical storm Imelda brought a second 1,000-year flood to the Houston area. The bathtub effects from closing the Bay with an outer-bay prototype will be magnified by more severe storms as the impacts of climate change unfold. GBPP provides resilience through redundancy should the outer-bay prototype need to remain open to minimize bathtub effects or fail to close during storm surges.

Multiple lines of defense provide redundancy to make the composite system safe to fail (Rising 2017). Rice University’s SSPEED Center proposed such a multi-prong system prototype (Figure 2B) to protect west and north Galveston Bay from storm surges. This prototype combines the outer-, mid-, and inner-bay ESS with NBS components, such as oyster reefs and barrier islands. The ESS components use gates to close the gaps between barrier islands, coastal levees, and elevated roads. This multi-gate prototype reduces bathtub effects because it closes only some smaller gates to mitigate localized storm surges as opposed to one large gate that disconnects the Bay from the Gulf completely. However, some of the proposed ESS components can still lead to minor bathtub effects and legal issues with the Texas Open Beaches Act.

Mobilizing governments to finance the costly outer-bay system can be challenging in a post-pandemic environment. It will take at least fifteen years to plan, design, and construct the outer-bay prototype. Closing the bay with the outer-bay prototype also introduces a false sense of security to deter proactive relocation and encourage developments (Rising 2015). Further, the outer-bay prototype could result in more loss of life should SLR render the system inadequate at some point in the future. The bathtub effects from the outer-bay and mid-bay prototypes could make pluvial and riverine flooding more severe. There is a need to use short-term and less-costly smaller-scale prototypes to alleviate bathtub effects while absorbing, as opposed to blocking, storm surge flooding. These smaller-scale prototypes can be upscaled and interconnected into larger-scale NBSs over time to reduce flood water flows and levels as storm surges intensify with SLR.

Most of the large-scale prototypes are outside of the purview of one jurisdiction, necessitating non-local funding from tax dollars. Projects funded by tax dollars need to be justified through public consensus and interest. Consequently, twelve years after Hurricane Ike, few prototypes have been implemented. Compared with the large-scale prototypes in front of high-water marks, smaller-scale prototypes behind are less costly and more likely to be financed by new developments or drainage improvement projects.

To mitigate pluvial flooding in the designated Areas for General Drainage Improvements (Figure 4), the Harris County Flood Control District (HCFCD) proposed many bond-funded projects for upscaling the stormwater detention capacities of internal drainage systems, including underground storm sewers and roadside ditches.

Figure 4.

Figure 4.

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Seabrook’s general drainage improvement areas west of Galveston Bay, Texas.

Source: Harris County Flood Control District and Alfrin Islam, June 2021.

Some of these HCDFD projects could have been replaced by interconnected blue-green-gray infrastructure components with depressed areas for detaining runoffs (Depietri and McPhearson 2017) through hardscaped ESS prototypes, such as floodable garages, floodable streets with elevated sidewalks, and sunken water plazas (Brody, Highfield, and Blessing 2022), and softscape NBS prototypes, such as greenways, green streets, and rain gardens (Nowogoński 2021; Taura, Ohme, and Shimatani 2021; Webber et al. 2020). The collective detention capacity of these prototypes can be increased by upscaling each component or adding components to the overall system (Golden and Hoghooghi 2018; Liu, Fryd, and Zhang 2019) to mitigate increasing street flood water levels over time. With SLR, oyster reefs and wetlands can migrate inland to transform smaller-scale NBS and ESS prototypes behind existing high-water marks into continuous greenways with parallel depressed swales as shallow water areas for attenuating storm surges.

Distilling Form-Based Codes from Publicly Acceptable Adaptive Landscape Prototypes

This study first distilled the aforementioned context-specific precedents into prototypes. During the two design games, the form-based codes were extracted from the most suitable prototypes based on the prototypes’ potential to positively transform existing and future site conditions: The prototype-specific suitability analysis involved articulating the extent to which each proposed prototype was suitable for transforming present weaknesses and future threats into short-term strengths and long-term opportunities for each proposed location and Seabrook. The design games used consensus-based participatory design toolkits with prototypes developed to facilitate the community visioning processes suggested by the FBCI (2021): Each participant from each design game table took turns placing a design game card (visually presenting a suitable prototype) at a suitable location on a paper map (with overlays of contextual information and flooding scenarios) until everyone agreed with the team outcome. For each design move, each participant had to justify the proposed prototype and location by using the prototype-specific suitability analysis based on each prototype’s potential to positively transform the site conditions. The use of prototypes enabled participants to contribute equally while minimizing institutional influences associated with the aforementioned competing precedents.

During the design games, city representatives, including administrators and design professionals, favored enabling adaptation in situ with smaller-scale ESS prototypes, such as floodable streets and plazas to minimize flood risks for new developments. County representatives, including administrators and professionals from engineering, planning, and environmental sciences, preferred to prevent costly buyouts and to keep people out of harm’s way by replacing flooded coastal developments with large-scale coastal greenways with parallel swales. The swales provide shallow water zones to accommodate migrating oyster reefs and wetlands and form multiple lines of defense with the greenways to help mitigate storm surge flooding without creating habitat squeeze or causing bathtub effects. Residents that participated in the design games included environmental, engineering, and design professionals and high school students from flood-prone neighborhoods. Both expert and non-expert residents preferred to implement smaller-scale NBS and ESS prototypes to facilitate more effective and timelier emergency evacuation. Emergency evacuation became the consensus-based response to storm surge flooding because it is necessary for either short-term adaptation in situ or long-term proactive relocation. All the aforementioned prototypes were integrated into an adaptive landscape system for facilitating emergency evacuation.

Evaluating Effectiveness of Form-Based Codes for Emergency Evacuation

To simulate the performances of the consensus-based adaptive landscape system from the two design games, the test case used 3 storm surge flooding scenarios based on 0, 5, and 10 linear feet of SLR (Figure 5). The simulation demonstrated that it is feasible for adaptive landscape components to increase in numbers and geographic extents to achieve emergency evacuation performance objectives measured by evacuation time and vulnerable population even as storm surges magnify with SLR.

Figure 5.

Figure 5.

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Performance of landscape form-based codes based on sea level rise scenarios.

Source: Adriana Hernandez, Daniel Douglas, Lauren Schulze, Clint McClellen, and Lead Author, June 2022.

Discussion

This test case demonstrated a feasible workflow and framework for mainstreaming form-based codes to facilitate adaptation pathways planning in communities prone to storm surge flooding even in the absence of development regulation. Design games were effective in distilling form-based codes from consensus-based adaptive landscape prototypes through selecting and siting game cards (representing prototypes as system components) with the same game rules (component-level suitability analysis and system-level performance criteria) shared by participants.

The test case also suggests that it was feasible to use this consensus-based adaptive landscape framework to delay the convergence of the storm surge, riverine, and pluvial flooding to provide more time to vulnerable population for more effective last-minute evacuation despite increasing storm surge flooding due to SLR. The test case workflow can be used by other flood-prone communities to expedite the generation and adoption of form-based codes for facilitating emergency evacuation in H-Transects designated for short-term in-situ adaptation without impeding long-term managed retreat for SLR.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Biographies

Author Biographies

Hope Hui Rising founded the Adaptive Water Urbanism Initiative, an integrated program of education, research, engagement, and design for adapting communities to the impacts of extreme events. She is an Arts and Humanities Fellow with the Division of Research.

Galen Newman is the director of the Center for Housing and Urban Development and professor and head of the Department of Landscape Architecture and Urban Planning at Texas A&M University. His research interests include community resilience, urban regeneration, land use science, spatial analytics, and built environment performance.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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