The National Academies

07/30/2024 | News release | Distributed by Public on 07/30/2024 14:33

Reviving the Los Angeles River: Engineering Alongside Nature and Society

Mitul Luhar is an alum of the The Grainger Foundation Frontiers of Engineering program and the New Voices program at the National Academies of Science, Engineering, and Medicine. He is an associate professor of aerospace and mechanical and civil and environmental engineering at the University of Southern California and holds the Henry Salvatori Early Career Chair.

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Reviving the Los Angeles River: Engineering Alongside Nature and Society

Perspectives| July 30, 2024
Much of the Los Angeles River is currently a concrete channel. Angelenos often joke that it is hardly a river, given that it is frequently dry and perhaps better known as the location for motorcycle and car chases in Hollywood blockbusters. Yet, the concrete channel serves an important purpose. The channel and multiple dams were put in place as flood control measures by the U.S. Army Corps of Engineers after a series of devastating storms in the early 1900s (Gumprecht 2001). The concrete channel fixed in place a river that was previously a dynamic landscape that frequently flooded and changed course. The denuded and straightened channel also reduced flow resistance, easing the passage of high flows towards San Pedro Bay.
In many ways, this modern incarnation of the LA River is doing its job. Despite a barrage of record-breaking storms over the past two winters (DeFlorio et al. 2024), careful management has ensured that the river does not go over its banks and flood surrounding neighborhoods. But there is growing recognition that the river could be so much more.
Reviving the LA River is a prime example of a large-scale infrastructure project that requires engineers to work alongside nature and society. Historically, the LA River served as a vital source of food and water for the Tongva people. A revived LA River can again serve as habitat for native vegetation and wildlife, improve water quality, aid water management, and contribute to cultural renewal. Naturalizing sections of the river could help reduce the impact of urban heat islands and provide valuable open recreational space. Of course, all of this must happen without increasing flood risk in a changing climate.
Mitul Luhar
Given the potential benefits, there is widespread support for a revival of the LA River. The U.S. Army Corps has conducted in-depth ecosystem restoration studies (USACE Los Angeles District 2015). The County of Los Angeles maintains a compelling LA River Master Plan (LA County Public Works 2022). The city and government agencies have purchased large sites adjacent to the river to enable restoration.[1] Despite these efforts, there is limited consensus among the project partners and the local community on how best to proceed.
Revitalizing the river is challenging for several reasons. Successful implementation requires a closely coordinated effort among expert practitioners spanning several disciplines. The design process must balance the priorities of many project partners as well as the local community. Moreover, there are significant constraints associated with redeveloping large parcels of land - some of which are polluted post-industrial sites - in the middle of a bustling metropolis. Many of these challenges are specific to the LA River. Yet, there are knowledge and process gaps common to all infrastructure projects requiring multi-functional nature-based solutions.

Challenges and Opportunities

Like all nature-based solutions, the river revitalization effort requires an alignment between engineering practice, the natural environment, and community impacts. From an engineering point of view, a primary consideration is the impact of any restoration (e.g., creating habitat islands, removing concrete, reintroducing vegetation) on flood risk. From an ecological point of view, the long-term success of any restoration effort is intrinsically linked to the prevailing flow regime and environmental conditions. A naturalized river is also likely to exhibit greater seasonal and interannual variability in flood risk and flow regime. Reliably predicting flood risk, restoration success, and river dynamics is central to the revitalization effort. This requires the development of a model for the LA River - a digital twin - that couples hydrology, hydraulics, sediment transport, water management practices, and ecosystem processes. This model must also capture the uncertainty introduced by climate change, future shifts in water use and management, and the risk from extreme events that stress multiple elements of the system. Moreover, the development and validation of such a model require datasets spanning flow, water quality, temperature, ground cover, etc., which are currently unavailable.
Even if a reliable predictive model can be developed, the design process requires optimization across multiple objectives (e.g., flood protection, habitat, community impact, and cost) that are often competing. Project partners are likely to prioritize these objectives differently, leading to potential conflicts. For the LA River, these challenges are exacerbated by additional constraints: the possibility of soil contamination and the presence of significant existing water and power infrastructure at the sites to be redeveloped. In addition, there are important knowledge and data gaps around the efficacy of nature-based infrastructure solutions. The long-term social and environmental benefits are hard to quantify (Lafortezza et al. 2018; Raymond et al. 2017) and the vulnerability to natural hazards is uncertain (Seddon et al. 2020). As a result, the evaluation of nature-based solutions does not easily fit within practices such as cost-benefit or life-cycle analyses (Kurth et al. 2024) that guide engineering design.
Societal impacts are particularly challenging to address in the design process. Many of the communities adjacent to the LA River are classified as environmentally vulnerable.[2] While river revitalization and ecosystem restoration efforts have the potential to alleviate some of these vulnerabilities, they can also create displacement and gentrification concerns. Further, community engagement is often limited early in the design process. This combination of factors can lead to reduced community acceptance of proposed solutions, despite the potential benefits.
While there are many challenges, the scale and scope of the LA River project also provide opportunities to rethink current practices. To enable effective communication and interaction between experts in different fields, new collaborative frameworks and tools need to be created. The design process must also be made more inclusive. Identifying community priorities and building trust throughout the design process is likely to yield greater acceptance of eventual solutions. Simultaneously, citizen science initiatives can be used to fill data gaps and increase engagement (NASEM 2018).

Tools and Technologies

The use of digital twins - digital models that replicate a real-world product or system - is increasingly common in engineering (Jiang et al. 2021). In the design phase, digital twins can be used for prototyping and lifecycle modeling. During operation, digital twins provide vital insights for monitoring and maintenance. For the LA River, digital models exist for traditional engineering considerations (e.g., hydraulics and flood risk, sediment transport). However, to create a digital twin for the river, these models must be extended to account for ecosystem processes, water management practices, and societal impact. Understanding and modeling these complex multi-sector dynamics is an emerging priority area for the wider scientific community (Reed et al. 2022). In the longer term, the digital twin can be augmented with in-situ, remote sensed, or crowdsourced data to identify potential risks and inform management decisions. Emerging data science, analytics, and fusion methods, including machine learning approaches, could play a vital role in this effort.
The development of the concrete channel was likely driven by engineers who used scaled physical models to optimize the flow path and minimize flood risk. However, the revitalization effort can benefit from the development of a co-design framework that is more interactive and inclusive. To be effective, this framework must integrate information from several disciplines, accommodate different presentation modalities, and function over a range of spatial or temporal scales. Modern augmented and virtual reality tools are well suited for addressing this need. They can be used to customize the information available for different audiences and enable users to experience design proposals in an immersive environment at their chosen scale. For example, technical experts may wish to combine simulation data, design schematics, and maps that show design constraints to inform decision making. Community members and government decision makers may be more interested in renderings of potential design solutions and clear performance metrics relevant to their priorities. In addition to serving as interactive and immersive information displays, these digital tools can also enable technical experts, community members, and project partners to propose modifications and leave comments that persist through different design iterations.
Figure 1. Physical models, simulations, and AR tools can be complementary tools for co-design and community engagement. Photographs by Gina Clyne courtesy of Clockshop's program "What Water Wants."
Digital twins and interfaces need not replace physical models entirely. Indeed, appropriately designed physical models can serve as effective platforms that bring project partners together and allow for interactive and insightful testing. In many ways, physical models, augmented reality interfaces, and reliable digital twins are complementary (see figure 1). Successful integration of these systems could generate a powerful and flexible design and management platform for the LA River.

The Role of Engineering Education

Perhaps most importantly, responding to the challenges and opportunities highlighted here requires emerging practitioners to have skillsets that go beyond the training provided in traditional engineering programs. Projects like the LA River redevelopment effort have lifecycles that span decades. This requires an understanding of how any solutions will function in a changing climate and society (Martin et al. 2022). Engineers working on such projects must also be able to incorporate knowledge from disciplines ranging from environmental science and ecology to economics and public health. This must be closely coupled with training in ethics, environmental justice, and an ability to work with diverse communities. The NAE Grand Challenges Scholars Program[3] and emerging One Health education initiatives (Villanueva-Cabezas et al. 2022) serve as useful blueprints for developing the broader perspective and leadership skills needed for meaningful impact.

Conclusion

Reviving the LA River serves as a benchmarking opportunity for the development of nature-based solutions that are climate resilient and simultaneously provide social, economic, and environmental benefits. While many of the challenges are location specific, the underlying research and training needs span all infrastructure projects requiring nature-based solutions. The design and implementation of such projects require modeling frameworks that enable evaluation across engineering, environmental, economic, and social dimensions. Ensuring that the solutions remain effective over their intended lifetime - and in a changing climate - requires novel monitoring and management approaches. Building consensus among project partners and community members requires inclusive and interactive collaboration tools. Lastly, all of this requires emerging engineering professionals to be comfortable working across disciplinary boundaries and have broader training in project management, community engagement, and leadership.

Acknowledgement

The author would like to thank collaborators Alex Robinson, Andreas Kratky, Gale Lucas, and the USC Public Exchange team (Monica Dean, Carling Monder). The team's work on the development of interactive models and design interfaces for the Los Angeles River and the establishment of an LA River Observatory is supported by the University of Southern California, Metabolic Studio, National Endowment for the Arts, City of Los Angeles Bureau of Engineering, U.S. Army Corps of Engineers, as well as the Mountains Recreation and Conservation Authority. The author would like to thank the NAE for providing this platform.

Disclaimer

The views expressed in this perspective are those of the author and not necessarily of the author's organization, the National Academy of Engineering (NAE), or the National Academies of Sciences, Engineering, and Medicine (the National Academies). This perspective is intended to help inform and stimulate discussion. It is not a report of the NAE or the National Academies.

References

DeFlorio MJ, Sengupta A, Castellano CM, Wang J, Zhang Z, Gershunov A, Guirguis K, Luna Niño R, Clemesha RE, Pan M, Xiao M. 2024. From California's extreme drought to major flooding: Evaluating and synthesizing experimental seasonal and subseasonal forecasts of landfalling atmospheric rivers and extreme precipitation during winter 2022/23. Bulletin of the American Meteorological Society 105(1):E84-104.
Gumprecht B. 2001. The Los Angeles River. Baltimore, MD: Johns Hopkins University Press.
Jiang Y, Yin S, Li K, Luo H, Kaynak O. 2021. Industrial applications of digital twins. Philosophical Transactions of the Royal Society A 379(2207):20200360.
Kurth MH, Piercy CD, Jackson CR, Lemasson BH, Harris BD. 2024. Life cycle management of natural infrastructure: assessment of state of practice and current tools. Frontiers in Built Environment 9:1181835.
LA County Public Works. 2022. LA River Master Plan.
Lafortezza R, Chen J, Van Den Bosch CK, Randrup TB. 2018. Nature-based solutions for resilient landscapes and cities. Environmental Research 165:431-41.
Martin MJ, Diem SJ, Karwat DM, Krieger EM, Rittschof CC, Bayon B, Aghazadeh M, Asensio O, Zeilkova TJ, Garcia‐Cazarin M, Alvelo Maurosa JG. 2022. The climate is changing. Engineering education needs to change as well. Journal of Engineering Education 111(4).
National Academies of Sciences, Engineering, and Medicine [NASEM]. 2018. Learning Through Citizen Science: Enhancing Opportunities by Design. Washington, DC: The National Academies Press.
Raymond CM, Frantzeskaki N, Kabisch N, Berry P, Breil M, Nita MR, Geneletti D, Calfapietra C. 2017. A framework for assessing and implementing the co-benefits of nature-based solutions in urban areas. Environmental Science and Policy 77:15-24.
Reed PM, Hadjimichael A, Moss RH, Monier E, Alba S, Brelsford C, Burleyson C, Cohen S, Dyreson A, Gold D, Gupta R. 2022. MultiSector dynamics: Scientific challenges and a research vision for 2030. A Community of Practice Supported by the United States Department of Energy's Office of Science.
Seddon N, Chausson A, Berry P, Girardin CA, Smith A, Turner B. 2020. Understanding the value and limits of nature-based solutions to climate change and other global challenges. Philosophical Transactions of the Royal Society B 375(1794):20190120.
USACE [U.S. Army Corps of Engineers] Los Angeles District. 2015. Los Angeles River Ecosystem Restoration: Integrated Feasibility Report.
Villanueva-Cabezas JP, Winkel KD, Campbell PT, Wiethoelter A, Pfeiffer C. 2022. One Health education should be early, inclusive, and holistic. The Lancet Planetary Health 6(3):e188-9.

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