Southern California could use single purpose grey infrastructure to help solve their water issues. While grey infrastructure is good at solving one problem, natural systems not only address the primary issue, they perform multiple services – providing co-benefits that generate broader public value.

As municipalities and regional governments transition towards a multi-purpose infrastructure, the region has an opportunity to integrate natural systems to capture and clean stormwater while also creating valuable social and environmental benefits in underserved communities.

Southern California’s Water Challenges: Quantity, Quality, & Reliability

Although an oversimplification, the region’s water challenges can fall in to three buckets (excuse the pun): water quantity, water quality, and water supply reliability.

Water Quantity

SoCal is not known for having a lot of rain in the first place, which limits the area’s ability to capture all of its water needs on-site, but given the amount of paved surfaces, when it does rain, much of this rainfall is turned into runoff. Despite the region’s vast network of dams and spreading grounds which capture billions of gallons per year, there is still room for improvement. If the water that currently flows to the ocean were cleaned of pollutants and infiltrated or directly reused, is could supply millions of people.

Water Quality

Stormwater picks up trash, bacteria, nutrients, chemicals, and heavy metals which then, if not treated on site, go in to rivers, beaches, and the ocean. These cause human health issues, hurt marine life, and degrade ecosystem functions.

Water Supply Reliability

Southern California residents rely heavily on imported water from the Sierra Mountains, the Central Valley and from states as far away as Colorado. As the climate changes, so does the predictability and variability of these alternative sources, which may disrupt supply going forward.

The Value of Nature-Based Systems

Green infrastructure (GI) has surfaced as a versatile solution for addressing the above stormwater challenges in the region. Unlike single purpose grey infrastructure, natural systems do more than tackle the primary problem at hand, generating a variety of financial, social, and environmental co-benefits beyond water quality and quantity...and, being economists, we like to put a dollar value on those impacts.

Water-Based Benefits from Green Infrastructure

Green infrastructure captures runoff and recharges the region’s groundwater, while also reducing the amount of pollutants reaching rivers and the ocean. There are financial, social, and environmental impacts that arise from this.

Other Social and Environmental Benefits from Green Infrastructure

The water-based benefits on their own may not always be enough to overcome the often-higher upfront capital cost of natural systems, which continues to be a hurdle in their wider implementation. Nevertheless, these nature-based solutions simultaneously generate a variety of co-benefits that create tangible value for a variety of stakeholders.

For example, these projects offer recreational amenities in areas that often lack green space, improve public health through exercise and reduced cardiovascular disease, they provide educational opportunities, reduce the urban heat island effect, attenuate flood risk, improve property values, as well as sequester carbon and remove harmful air pollutants.

A larger (but not necessarily complete) suite of impacts from nature-based infrastructure can be seen below.

Putting Theory in to Practice: Showing the True Value of a Project in Southern California

The team at Autocase recently valued the Triple Bottom Line impacts for a large spreading ground enhancement project – one of many green infrastructure projects currently in design in the region. This particular project will increase water conservation by infiltrating an additional 8,000 acre-feet/yr (enough to supply 24,000 homes per year) while also including landscaping, and recreation & education opportunities. The triple bottom line results help build a financial case for similar projects that integrate natural systems.

The results below are for the 50-yr lifespan of the project. Interestingly, the upfront and ongoing maintenance costs (around $59m) are outweighed merely by the financial value of water savings (around $230m). Given the large scale of the project, the social value of water supply reliability is around $60m, and the avoided emissions due to capturing water closer to the end use is valued at around $4m. Once the other social and environmental co-benefits are valued – like recreation, urban heat island, property value etc., it makes for a compelling case to invest in natural systems, with the overall triple bottom line value at almost $250m. For every dollar spent, the project is estimated to return $5.2 in benefits.

Work with Nature, Not Against it

These kinds of results illustrate that natural systems can be integrated to solve major challenges while also saving money and serving the community by creating broader public value. When assessed solely on first cost, it can be difficult to justify their implementation, but once the true value is identified, measured, and monetized, it is clear to see that these projects perform valuable social functions over and above their primary goal – often in communities that lack green space.

By valuing impacts in dollar terms, a diverse portfolio of projects can now 1) be compared consistently and transparently in an apples to apples way, 2) compete for funding, and 3) be prioritized in such a way to generate the greatest bang from the public buck.

Ultimately it’s rarely a binary choice between grey vs. natural systems i.e. the idea isn’t only to use nature or only to use grey. Instead it should be about recognizing the value that natural systems provide and integrating them in to grey solutions to enhance infrastructure projects.

This concept can be summed up nicely by E.F. Schumacher:

“Modern man does not experience himself as a part of nature but as an outside force destined to dominate and conquer it. He even talks of a battle with nature, forgetting that, if he won the battle, he would find himself on the losing side.”
E. F. Schumacher (1973). Small is Beautiful

Simon Fowell, Economist at Autocase