Los Angeles has long been known as a city of car culture, rooted in the 6,500 miles of streets that cross, wind and grind across its urban surface. For those living in the City of Angels, these streets have historically been a locus of civic activity, an extension of homes and businesses, and a catalyst for community building and placemaking. As cities adapt and augment their infrastructure in response to climate change, population growth and multi-modal transit expansion, streets present unique opportunities and challenges for transforming cities. To meet these and other challenges, Los Angeles streets must expand their value and utility. Standing initiatives like Road Diets and Green Streets play a crucial role in combating the heat island effect, ameliorating air quality, decreasing the severity of storm events and promoting urban wildlife. Although these strategies are successful, they are only the beginning of a reinvention of the street as green infrastructure.
This essay explores new approaches for improving the ecology of streets, using case studies along Vermont Avenue in Los Angeles. As engineers, landscape architects, planners and urban designers, we must rapidly expand our toolbox of design strategies so that street design can strengthen ecological, social and economic systems, improving environmental stewardship and living conditions for city dwellers, particularly our more vulnerable communities.
If reinvention of such a vast street network is to be realised within a reasonable time frame, we must also be strategic in how we promote its adoption. We must target integration across the wide variety of projects and activities that alter the ecology of streets. For example, some Cap-and-Trade funding from California’s greenhouse gas mitigation programmes has been leveraged by Los Angeles Sanitation & Environment (LASAN) to plant more than 8,000 street trees in high-pollution, low tree-canopy neighbourhoods since 2015. Similarly, Los Angeles recently voter-approved the storm water budget, Measure W, that aims to invest heavily in green infrastructure along streets. We must also leverage our rapidly expanding urban data capabilities to identify locations with unique opportunities and challenges. LASAN is also creating an Ecotopes database of detailed urban ecological data layers to support optimizing urban ecology throughout the city and informs the following analysis.
Because of its sheer size and practical importance, Vermont Avenue – a prodigious 23.3-mile arterial, running through over 30 distinct neighbourhoods, and one of Los Angeles’s busiest and oldest streets – provides the perfect model for exploring the transformative potential of street design.
Due to their high traffic volumes, large portions of arterial streets are often challenging, or inappropriate, for creating vibrant civic or pedestrian-oriented spaces. Along three distinct yet equally overlooked portions of Vermont Avenue, three case studies for ecological strategies emerge: a broad landscape median, a remnant urban natural area and a lost creek. For each portion, we draw from personal experience, historical precedent and the Ecotopes database to discuss context-sensitive methods of promoting urban ecology while improving the pedestrian experience and preserving the viability of auto travel.
The Vermont Corridor: Three Urban Ecological Street Design Case Studies
1. A Streetscape Matrix of Diverse Environmental Benefits
One of the most pervasive arguments in favour of greening cities is the proven causative link between an increase in green space and positive effects on mental health and wellbeing. The community of Westmont runs between Manchester Avenue and Imperial Highway, with Vermont as its eastern border. It bears an alarmingly disproportionate homicide rate for its population of 31,467 and footprint of 1.84 square miles. While street design cannot change the underlying history of socio-economic conditions in a neighbourhood, it can make the air cleaner and cooler, provide bike lanes and dedicated pedestrian areas and simplify circulation between schools, libraries, churches and local businesses.
There is no one-size-fits-all strategy here, as each block has its own unique needs, so a matrix of different approaches is appropriate. The avenue and landscape median are significantly widened in this stretch of Vermont, a remnant of the old Yellow Car trolley line that ran straight down its centre. Because of the extensive area of available land here, the transformation does not have to be complicated: concentrate traffic lanes in the centre, convert existing twin bike lanes on each side of the street to separated bike paths and plant extensive street trees. These modifications will increase mobility, improve air quality and buffer residential frontages from the busy street.
Arterial streets can be challenging because of varying demands put on them by diverse adjacent land use. Nearby businesses do not want their signage, parking or entries obscured, auto commuters refuse to be slowed or rerouted and any expanded maintenance of right of ways poses logistical and financial challenges considering the vastness of Los Angeles’s street network. A matrix approach includes tailored streetscape modifications for each type of adjacent land use frontage: for a school, bulb out a parklet with picnic tables and dry creek beds and a nature education garden; for a business, keep a side frontage street for parking and preserve signage visibility by planting high-canopy trees with open views beneath; for a fire station, add warning signage for the bike lanes and keep access wide and unobstructed. This approach would knit together patches of natural habitat and drainages as well, a vision for Vermont also laid out in LASAN’s award winning ‘Greenways to Arterials Stormwater System Plan (GRASS)’, and potential funding source in Measure W. As these streetscapes grow in, ecological systems will have the chance to flourish, reducing the urban heat island, treating storm water, cleaning and cooling the air and bringing access to nature with associated mental, physical and community health benefits.
2. Fostering Urban Ecological Corridors
On the southern end of Vermont, near the intersection of the 91 freeway, a small patch of historic wetlands is nestled into the residential fabric. The last intact remnant of the former Dominguez Slough, the Gardena Willows Wetland Preserve is also one of the last remaining ‘natural’ portions of the entire watershed, 96% of which is now covered with concrete and man-made structures. It was saved by local residents, who today run bird and butterfly counts, hold clean-ups, clear out invasive species and generally protect the space. Today, Vermont acts as a barrier to wildlife that might cross into the nearby Dominguez Channel, as well as nearby residents who might visit the preserve. As the City of Los Angeles strives to establish a more complete network of greenways and ecological corridors along the LA River and its tributaries, the Gardena Willows Wetland Preserve presents a key opportunity to connect two key urban habitat features.
Because of this complex natural history and current local support, we suggest a simple but profound transformation: building two ‘bridges’ over Vermont Avenue. People, wildlife and natural processes need space to move within and through cities, but roads fragment habitat, increase edge conditions, foster inbreeding depression and generally make it more difficult to sustain biodiversity.
By making the street ‘invisible’, or permeable to wildlife at multiple levels, the wetlands would regain the critical functionality of movement. This would enhance an already treasured public natural space and create a vital link for the Dominguez Channel.
With the addition of a pedestrian and wildlife bridge over the street and wildlife-permeable openings beneath the street, the two sides could connect, creating a network for urban biodiversity without interrupting the flow of traffic. Such a concept places movement of pedestrians and access to nature on par with that of automobiles, a policy we could envision for all locations where streets cross urban habitat corridors in Los Angeles.
3. Placemaking and Climate Change Adaptation with a Lost Creek
Before the establishment of its most iconic streets – Sunset, Pico, Beverly, Mulholland – Los Angeles was checkered with silvery wetlands and etched with springs and streams. The city we know today – a concrete grid with places that have little connection to the land – was dug, drained and built up from those wetlands and streams. On a short stretch of Vermont between 5th and 6th Streets, a subterranean box culvert 9 ft in diameter is all that remains of the Arroyo de la Sacatela, a historic wetland and creek. Despite its proximity to schools, health care centres, a subway stop and a dense residential neighbourhood, this block is almost completely paved over. All that concrete amplifies the urban heat island effect and provides a poor pedestrian experience. Because creeks are necessarily lower than the areas around them, water continues to collect here even though the waterway itself is no longer visible and the neighbourhood often suffers from nuisance street flooding during heavy rain conditions. The broader watershed is at risk of more substantial flood hazards with climate change- driven stronger storms in coming decades.
Cities from Seoul to San Antonio are ‘daylighting’ these lost creeks for both environmental benefits (reducing the heat island effect, for example), and as a placemaking strategy. In some cases, this technique can be combined with other street improvements to quickly transform an urban environment into a more natural one. One strategy would be to daylight the creek along the east side of Vermont, integrating it as a central open space feature for a major pedestrian-oriented, public-private infill development on adjacent parcels. This feature would connect nearby parks and neighbourhoods in a vibrant new creek greenway that builds a sense of place in an area currently dominated by busy, unappealing arterial street and parking lots.
Since the creek at Vermont is significantly below grade, creating a sunken greenway would be the most common approach to daylighting. However, considering our climate change future, we propose a more radical rethinking of the street to create a more pedestrian friendly greenway: sinking the northbound lanes of Vermont Avenue. During stronger future flood events, Vermont’s northbound lanes would be closed and allowed to flood with the creek, contributing storage capacity for excess water, while southbound lanes would remain open.
Such concepts have been proposed for freeways adjacent to the nearby Los Angeles River as a way to address projected insufficient flood capacity there. This solution could help mitigate potential climate change-driven future flood damage in broader Ballona Creek watershed while maintaining the greenway at grade, a more appealing condition for users.
At the time of this publication, lost wetlands in Los Angeles’ nearby MacArthur Park, Lafayette Park and Shatto Creek have begun to be recovered as new amenities that also provide ecosystem services.
As cities evolve so does infrastructure and we must present a compelling case for streets as an untapped opportunity. Covering more than 20% of the urban footprint, street rights of way are the single largest type of public land in built areas of Los Angeles. This mobility space has been part of radical reinventions of the city multiple times in the past and must do so again. The iconic Red Car streetcar network fostered mass development and in-migration to the vast agricultural regions at the turn of the 20th century. Construction of the freeway network in the 1950s promised to alleviate the connectivity challenges of such rapid development. Now, our approach to mobility infrastructure is evolving again to emphasise, reduced pollution and auto congestion and achieve a triple bottom line of social, economic and ecological benefits. By taking a key arterial passage and breaking down three distinct sites and strategies, one can see how every site has an ecological story that can become a basis for design and placemaking. In light of emerging environmental and socio-economic challenges, it is essential that engineers, landscape architects, planners and urban designers continue to expand such integrated analysis and placemaking considerations and once again reinvent cities through streets.
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