Distinguishing Built Environment from Infrastructure for Urban Resilience

Definitions, Frameworks, and Project vs System

In order to provide more effective strategies for urban resilience, the terms ‘infrastructure’, ‘built environment’, and ‘green infrastructure’ require context when discussing urban resilience, urban metabolism, clean energy transitions, and/or sustainability goals. The first two terms are often used interchangeably, where infrastructure can be broadly defined as "the physical components of interrelated systems providing commodities and services essential to enable, sustain, or enhance societal living conditions". Infrastructure can also be further divided into horizontal infrastructure (HI), e.g. roads, pipes, and lines (buried and overhead); and vertical infrastructure (VI), e.g., buildings. While built-environment (BE) is defined as “…those surroundings created for humans, by humans, and to be used for human activity.” The built environment determines how we move, work, convene, play, and otherwise conduct our daily lives – in other words, the physical design of cities impacts our behavior. While there is overlap between infrastructure and built environment, the two key distinctions are the professions that have chosen one term over the other, and the perspective that each of these professions brings regarding integrating nature, reliability, and livability into designs and plans. This is represented in Figure 1.

Figure 1: Venn Diagram of Horizontal and Vertical Infrastructure and the Built Environment

As shown on Figure 1, the integration of nature progresses from ‘conflict’ and focus on reliability in HI where the engineer views tree roots as an adversary to their designs for water mains, roads and sidewalks that must be conquered; to the urban planner that attempts to integrate livability, green corridors, or even envisions a ‘green city’ (BE). There is a conflict when nature is integrated post HI design, e.g. the pristine road cross section without considering the natural consequences of low-impact design five years post construction.

Within the intersection of infrastructure and the built environment is VI – the domain of primarily architects who respond to a desire to integrate green buildings, beyond just green roofs and landscaping, while maintaining reliable access to transit and connections to HI. Transit needs to be distinguished by Moving Assets (like trains, buses, bikes, or boats) from Fixed Assets (like rail, roads, sidewalks, or canals). Where the moving assets, unless human powered, are the sources of emissions (whether Scope 1 or 2) and sustainability efforts and policy. While the fixed assets straddle characterization; to engineers this is the realm of HI and to planners this is the realm of BE. Also fitting into this intersection, in Figure 1, is Green Infrastructure (GI) that has been severely limited in national certifications as belonging to just the stormwater sector (HI), but is used for urban low-impact design in the BE. As discussed below, GI can be (and is) applied to all sectors of infrastructure, both within the urban boundaries and outside the periphery (e.g. constructed/mitigated wetlands for wastewater/water supply engineers).

Integration of Projects into Systems, and Transitions

Consider the frameworks associated with HI, VI, and BE (not exhaustive, just examples). Engineers have turned to the Envision checklist for HI, architects continue to use the LEED[1] frameworks for VI, and planners are finding ways to include Green Zones[2] and EcoDistrict for BE. And, while all of these frameworks are excellent at the project level, there needs to be an understanding as to where each project fits into the urban systems[3]. The difference being that, in a system, multiple assets all have to function as a whole and the weakest-link in that system dictates overall resilience. This can be seen in multiple global examples of system failures; Cape Town’s Day Zero, multiple cities in India, Flint, Michigan. For buildings that compose the VI, even though they contain systems, they can be approached as a project. That is, buildings are not interconnected as in a system where failure of one does not lead to failure of all. What is the true value of a sustainable project, i.e. one asset, that must work within a larger system?

By expanding the view of infrastructure outside of the city boundaries, as shown in Figure 2, it is clear that no city is sustainable or resilient without considering the inflows and outflows of natural resources and wastes. Where infrastructure serves as the conduit by which these resources flow. These transitions[4] better illustrate a city’s ‘metabolism’ and connection to the environment, and where infrastructure is, or is not, in conflict with nature. Below Figure 2 is a brief (again, not exhaustive) summary of the infrastructure transitions and where the impacts of policy, or business decisions, may be visible in one transition, but the environmental impacts felt in another. Using Figure 2 as a guide, consider how nature is/is not in conflict with urban resilience and sustainability goals across these infrastructure transitions.

Figure 2: Infrastructure Transitions in the Urban Metabolism

· Natural Resources: The source of all fuel, food, materials, water, and air for all cities.

o Sustainability concern: In order to maintain equilibrium and quality between supply and demand, a goal is to return waste as resource, i.e. cradle-to-cradle.

o Resilience concern: In addition to the demand on resources, the potential destruction of resources due to climate change, or due to collocation of infrastructure (see Transmission) are threats.

· Supply: This is where potable water, energy, construction materials and communications originate as a refined product for consumption. Being the source of larger systems, this transition is defined by large projects, e.g. dams, thermal powerplants, and data centers. And while there are dams and peak power stations within a city, the watershed and fuels come from outside the city boundaries.

o Sustainability concern: This transition is where the key policy and business decisions are made that impacts urban sustainability and global climate change, e.g. price point of coal vs renewables, or developing new water sources.

o Resilience concern: As this transition is characterized by larger visible and critical projects (and discerning between potable water dams vs irrigation dams or flood levees), FEMA’s Hazard Mitigation Plan (HMP) category of ‘manmade’ is a concern.

· Transmission: Transmission refers to the movement of refined resources from plant to a point of local distribution. For electricity, this is between the power plant to the sub-stations, and for water moving from larger trunk lines to lesser diameter mains.

o Sustainability concern: Reduce the loss of energy and water losses.

o Resilience concern: In conflict with nature, e.g. the Camp Fire resulted from PG&E’s overhead transmission lines that sparked the massive wildfire.

· Distribution: These are the horizontal infrastructure systems in a city, often buried below our roads, that connect the supply to the end-user. For water, energy, construction materials, and data, the end-user are residents, commercial, industrial and governmental.

o Sustainability concern: These assets simply convey the result of the decisions made in the Supply transition, i.e. a copper wire works the same whether the electron is generated by fossil-fuel or renewables. The focus is on increasing the longevity (aka, economic life) of the materials that comprise the assets in horizontal infrastructure, these efforts are minimal compared to the threat of aging and decaying infrastructure.

o Resilience concern: A key reason why aging infrastructure is an issue is that city’s do not have a framework to assess the impact of these vulnerabilities. Even FEMA’s guidance for HMP does not require an overview of aging infrastructure in hazard analyses despite the potential of failing infrastructure to exacerbate disasters.

· Demand/Supply: As resources are transmitted to the end-user, they are consumed and then this transition becomes the supply for the wasted by-products. Fluid waste is sent back through the distribution transition via pipes, municipal solid waste via roads, and combustion via air.

o Sustainability concern: What is consumed in the Demand transition is determined in the Supply Transition. How much is consumed is behavioral. The flow of wastes now have to be categorized as contributing to a degraded urban air quality index (AQI) and Scope 1 carbon, or Scope 2. The solid and fluid wastes characterized as cradle-to-cradle, or cradle-to-grave, in environmental life-cycle assessment (LCA) terminology.

o Resilience concern: The infrastructure that connects a building, industry, or residence to the horizontal infrastructure is privately owned. So, often while a water or gas utility may be upgrading their infrastructure, it is the ‘final meter’ of infrastructure that can cause lead contamination in water, or gas explosions.

· Green Infrastructure: While ‘green infrastructure’ has been regulated to just the stormwater sector , it is worth noting in Figure 2 the distinction of low-impact design as a welcomed natural element in the Built Environment, while the HI is better characterized by mitigated/constructed wetlands relegated to the periphery or outside by wastewater/water supply engineers. Note: the next blog will cover how GI can, and should be integrated into all sectors of infrastructure.

In summary, this blog just sets the terminology and connections between the flows of resources and a city's/region's infrastructure systems. By getting planners, engineers, and architects to view connections of flows and emissions, what is in boundary of a city and where are the regional connections, there can be more overlap with how cities approach clean air, carbon footprints, urban metabolism studies, and similar resilience and sustainability policies. Although not incorporated into this blog, but perhaps the next, an interesting comparison of the Department of Homeland Security's 16 Sectors of Critical Infrastructure and ASCE's Report Card 16 Categories of infrastructure scores, and how they relate to Figure 2.

[1] Although ND is for an area, and RELi is building resilience, neither analyzes the vulnerabilities of the surrounding HI

[1] Not to be confused with downtown Baghdad

[1] Noun. an assemblage or combination of things or parts forming a complex or unitary whole

[1] Noun. movement, passage, or change from one position, state, stage, subject, concept, etc., to another; change