My first Substack publication, The Climate Landscape, explored various themes related to our changing climate and landscape architecture to examine nature-based solutions to climate change impacts. I recently decided to shelve that particular project and focus exclusively on writing about hidden hydrology; however, a few of those early essays were worth retaining here as they showed good overlap and connections between the two topics.

There is a direct connection between our cities’ buried and lost rivers and climate change. I touched on climate here previously in this post “Lost Rivers for Underground Energy. It took me some time to make a direct connection between my research on climate and lost waterways until more recently, and the revelation allowed me to weave together these two passions.

I’ve continued connecting the dots and trying to build a case for the importance of historical ecology and hidden hydrology in being the locus for solutions to contemporary issues, and not just focused on nostalgia. One aspect of this is looking first at causes and effects — looking back at the erasure of waterways from cities and demonstrating that the loss of ecological and hydrological systems exacerbates climate impacts such as urban heat, flooding, and sea level rise. I also looked forward to showing the patterns of historical hydrological systems that can act as frameworks for innovative climate solutions to provide adaptation and mitigation opportunities. The idea of “hydrological retro-futures” is the term I chose for this backward-forward process, which allows us to connect the historical ecology to the modern metropolis and tell these stories in an engaging, visual format.

One aspect of this project is visual. By using various graphical generative AI resources like DALL-E (see image below), I have been creating speculative images of hidden hydrology in the urban context, and exploring ways that revealing, restoring, and reconnecting with lost rivers can help us imagine the potential visual impacts that could be gained. I will share more in-depth on this project and some of the interesting graphics in a later post.

The other aspect is research and case-study-based. Brainstorming a few key topics areas, I will continue to explore here, including:

• MICROCLIMATE COOLINGThe daylighted streams will restore ecosystem services lost when buried, such as the presence of cooling surface water and vegetation that can aid in mitigating urban heat islands.
• FLOOD STORAGE CAPACITYDaylighting streams and springs currently in pipes will increase the capacity of infrastructure systems and make them more effective for flood resilience.
• SEA LEVEL RISEAreas of made-land in cities as a proxy for areas of flooding due to SLR and storm surge and ways to adapt these to absorb with more resilience
• WATER HARVESTING TO SUPPORT URBAN BIODIVERSITYDiversion of water that would be piped into uses for support of landscape vegetation and urban greening
• WATER USE FOR COOLING ENVIRONMENTSTapping into water from subsurface water pipes to help cool cities – use in pools, water features, misters, etc.
• WATER FOR HEATING & COOLING BUILDINGSUsing water from buried sewer pipes for heating buildings
• PALEO VALLEYSLooking at hidden ancient river valleys as sources for groundwater recharge and storage as new aquifers

By exploring these topics, I aim to gather feedback and generate a complete toolkit of solutions that can provide designers, planners, and policy-makers with options that work in multiple climates and scales and provide cascading benefits when implemented. I’d be interested to know of other topics and solution areas out there beyond this list, as well as any case studies, writings, or research on these topics.

Below are a handful of previous stories that cover some of these topics.

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ANCIENT WATERWAYS FOR COOLING CITIES

A recent article in Fast Company outlines the idea of “How ancient waterways could be tapped to cool scorching cities”. The focus is on new scanning methods to reveal buried streams and ‘ancient waterways’ and how to see the hidden infrastructure and potentially repurpose the water for climate change adaptation strategies. The group leading this effort is Cool City, an offshoot of the Korean Pavilion as part of the 2021 Venice Biennale, with projects using mapping underway in both Naples and Seoul. The unique idea here is to use handheld 3D scanning technology to provide more detailed scans of systems and then to use the gathered data to inform decisions for climate.

There’s merit to this as a way of approaching climate change through the use of these buried systems, both as a resource for water for irrigation and a passive cooling system and as a way to increase pipe capacity by removing underground streams through daylighting which frees up vital volume for additional stormwater management.

Mapping these has been done for many years, either as a GIS exercise with overlays of historical maps on current conditions and subsequent field verification or looking at current sewer and water and combined systems. This provides a good working system network to understand this hidden potential but not forgotten water in the city. Still, Cool City is taking it to the next level, as mentioned in the article, quoting a project collaborator, Nick De Pace, a professor of architecture and landscape architecture at the Rhode Island School of Design:

“Buried streams and old waterways are not totally lost to time. Many cities have maps showing where a former creek has been shunted into an underground tunnel to make way for aboveground urban development, for example. But De Pace says many of these maps are imprecise, and the new digital scanning and mapping of the Cool City project can bring much more actionable detail to buried streams, aqueducts, and springs. By using this water to irrigate green roofs, parks, and other urban vegetation, cities can counterbalance their heat-trapping hardscapes.”

A low-resolution snapshot of the scan below shows how compelling this composite imagery may be, showing the spaces above and below. Does it aid in climate planning, maybe? They mention that it can be used for irrigation, for more green spaces to mitigate urban heat islands, and for having more water on the surface to reduce heat and provide more cooling. Additionally, the mix of green and blue infrastructure systems can tap into the buried water to help adapt to climate change impacts.

I wonder, however, how feasible it will be to scan much of the sub-surface infrastructure as proposed above by Cool City, as it’s a mixed bag of small and large pipes and some more expansive and cavernous sewers, depending on the location and the era in which they were implemented. It’s a question to me if it is helpful to have 3D versions of these systems, or is mapping or modeling adequate to see the potential system components and flows and determine how it can be ‘tapped’ to become a tool to fight climate change?

3D scanning is an excellent visualization tool, as it is often difficult to imagine what lies beneath, which is less compelling than a line on a map. As mentioned in the article, understanding the available water resources more clearly is half the battle. The next part is how to operationalize this water for climate strategies. I am interested in seeing more from Cool City, how the technology works, and what solutions come up for using hidden hydrology for climate solutions.

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DETROIT: BURIED BUT NOT DEAD

Connecting the dots of Hidden Hydrology and Climate Change, a recent article makes the link between buried streams and wetlands and flood risk while investigating the inequitable distribution of risk by overlaying redlining map data. A recent article focused on Detroit dives into this connection. (“Buried but not dead: The impact of stream and wetland loss on flood risk in redlined neighborhoods” by Jacob Napieralski, Atreyi Guin, and Catherine Sulich; City and Environment Interactions, January 2024.)

While tying flooding to historically buried waterways isn’t novel, this is a unique idea, using mapping to overlay the Home Owners’ Loan Corporation (HOLC) maps showing redlining categories, which are well-documented spatial histories of racial and socioeconomic discrimination. The researchers used these factors (buried streams and redlining grade) as two of the criteria for flood risk along with proximity to coastal zones and intensity of vegetative cover.

The article is a deep dive, so I will skim on the surface with a bit on the methodology and findings, which are engaging and would be replicable anywhere using similar criteria. The mapping processes, including mapping and DEMs, were interesting. The inference of buried water bodies and flood risk has been borne out in recent events. The authors explain the connections between mapping and current flood risk:

“Although the actual stream channel or wetland surface were buried and built upon, high resolution elevation models (e.g., LiDAR) can be used to reveal the remnants of distinct depressions from these structures, such as meandering stream valleys, in heavily urbanized landscapes. The authors assume that, although no longer occupied by active streams or wetlands, residential homes built on buried stream valleys will experience an elevated probability of flood risk not included in floodplain maps, but also that the process of burial and removal were influenced by income and race embedded in some of the racist housing policies of the 1930s and 1940s.”

The flood risk data came from First Street Foundation’s Flood Factor, which would be good to explore in more detail. As described, the flood risk of parcels is rated 1 to 10 based on the chance of flooding in a time interval. There were also additional criteria, as mentioned, with coastal proximity, using available data, and vegetation density using Normalized Difference Vegetation Index (NDVI) data to describe the level of vegetation—more on both of these in the article, along with all the analyses.

The results reinforce other narratives of disproportionate risk tied to redlining districts that had more marginalized populations. The level of parcels at risk in zones C and D from the HOLC maps, although the amount of burial varied with the presence of most buried streams in HOLC Grade A & B and more buried wetlands in HOLC Grades C & D. As the authors mention:

“Flood risk is disproportionately distributed, caused in part by outlawed, racist housing policies. Understanding where risk is highest can help identify optimum locations for adaptation measures to minimize flood damage in these neighborhoods.”

This does bring up why mapping these streams is important, and the connections to climate change, although not overt, are implied as changes in precipitation and storm intensity make flood risks more frequent and more damaging. As the authors conclude (with a nice reference to hidden hydrology (citation please), the “…role of redlining in present day flood risk applies to cities throughout the United States, as does the importance of mapping ghost streams and wetlands to inform residents of the role “hidden hydrology” may play in increasing flood risk.”

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SAVING SWAMPS TO SAVE OURSELVES

It was a treat to read one of my favorite authors, Annie Proulx (Swamps can protect against climate change if we only let them, New Yorker – 06.27.22), discussing wetlands and their potential for climate change protection. She includes tales of killer herons, stolen rafts, and evocative ideas on our complex relationship with swamps, noting that “Many modern Americans do not like swamps, herons or no herons, and experience discomfort, irritation, bewilderment, and frustration when coaxed or forced into one…”

Swamps were not always reviled or out of favor, as Proulx recounts, in particular the views of Henry David Thoreau, on the subject:

“Thoreau has been called the patron saint of swamps, because in them he found the deepest kind of beauty and interest. He wrote of his fondness for swamps throughout his life, most feelingly in his essay “Walking”: “Yes, though you may think me perverse, if it were proposed to me to dwell in the neighborhood of the most beautiful garden that ever human art contrived, or else of a Dismal Swamp, I should certainly decide for the swamp.”

The connection to hidden hydrology lies in the massive loss of wetlands and the subsequent loss of function to reduce carbon and the numerous ecosystem services beyond that are provided by wetlands in filtering and mediating water in our landscapes. Development in the US meant filling wetlands for farmland, pasture, and eventually cities. The swamps often were a barrier to progress and Proulx notes:

“Across the country, the ongoing stories of vile adventures in the muck made it clear to military, government, and citizenry that something had to be done about the swamps so universally detested. Everywhere there were horrendous mixtures of fen, bog, swamp, river, pond, lake, and human frustration. This was a country of rich, absorbent wetlands that increasingly no one wanted.”

As this occurred, there were impacts, but climate change, and sea level rise in particular, exacerbates flooding, and filled-in wetlands at the margins are poor habitats for the buildings or fields we placed on them that are now in danger of being washed away with more intense storms. There were impacts to landscapes and plantings that reduced habitat. Beyond biodiversity loss, humans will feel the overall loss of resilience more acutely. Still, it is hard to save or restore these landscapes, as Proulx notes in her story of the Black Swamp.

“One authority on water, William Mitsch, has suggested that if ten per cent of the old Black Swamp soils were allowed to become wetlands again they would cleanse the runoff, yet Ohioans remain powerfully anti-wetland. Even private efforts to restore small wetland areas are met with neighbors’ complaints about noisy frogs and fears of flooding.”

Related are mangroves, which are also summarily destroyed, taking with them the ability to reduce storm surges and protect coastal areas in places like the Everglades. As described: “Mangrove swamps have been called the earth’s most important ecosystem, because they form a bristling wall that stabilizes the land’s edge and protects shorelines from hurricanes and erosion, and because they are breeding grounds and protective nurseries for thousands of species, including barracuda, tarpon, snook, crabs, shrimp, and shellfish. They take the full brunt of most storms and hurricanes, and generally survive—but not always.”

Larger, more intense hurricanes can damage mangrove areas with salt or sediment intrusion, reducing their ability to regenerate and removing their support for biodiversity. While natural disasters are a risk, development still threatens these areas despite mounting evidence of their benefits.

“Although climate researchers see mangrove swamps as crucially important frontline defenses against rising seawater and as superior absorbers of CO2—they are five times more efficient than tropical forests—they are in big trouble, and mangrove removal is a constant threat.”

The conclusion for Proulx is to re-establish our love of the swamp, and connect the existential threat of climate change to our ways of life to the natural systems we destroy in the process. Protecting what is there in terms of wetlands and mangroves left standing is the first goal, as well as restoring and expanding these valuable ecosystems, all of which are possible, even necessary as adaptation and mitigation strategies. Proulx ends with a call to action we can all heed:

“It is usual to think of the vast wetland losses as a tragedy, with hopeless conviction that the past cannot be retrieved. Tragic, indeed, and part of our climate-change anguish. But as we learn how valuable wetlands are in softening the shocks of the changing climate, and how eagerly the natural world responds to concerned care, perhaps we can shift the weight of wetland destruction from inevitable to “not on my watch.” Can we become Thoreauvian enough to see wetlands as desirable landscapes that protect the earth while refreshing our joy in existence? For conservationists the world over, finding this joy is central to having a life well lived.”

Note: This post was originally posted on Substack on 12/17/24 and added to the Hidden Hydrology website on 04/22/25.