The idea of Detroit’s Ghost streams work bridges my two interests by connecting the dots of Hidden Hydrology and Climate Change, a topic that I will revisit often. The post discusses research in Detroit, Michigan, that connects buried streams and flood risks, using historical ecological information overlaid with redlining map data to show the potential negative impacts on historically marginalized communities.
The basis of the research is what are known as ‘redlining’ maps. For a little background, the Home Owners’ Loan Corporation (HOLC) was a government agency created to assess financial risk for mortgage lending for real estate. The tool was used to systematically institutionalize racist policies in cities around the United States by assessing areas inhabited by people of color, poor, and immigrants as much higher risk than those where rich, white residents lived. The process led to disproportionate investment in low-risk neighborhoods and marginalization in those deemed ‘hazardous’ or ‘high-risk’ zones, which ultimately created concentrated areas of poverty through a lack of economic opportunities. The redlining has become a shorthand for the inequity of communities, and mapping allows for looking at how these historical impacts persist in cities today.
The research overlays these maps with other data to extract how the legacy of racist home lending in the past has created more risk of impacts like flooding today. The goal of the study was “… to determine whether a history of waterway burial and/or redlining influenced the overall flood risk of communities today.” The data revealed that the burial of streams and wetlands did impact current risks in the historically marginalized communities. As Napieralski mentions in the podcast:
“Flood risk is very intricately linked to history, and by ignoring history we may be missing some clues that help us move forward.”
Rather than dwell on the negative, the authors mention the positive side of the analysis, noting that most communities have this data and that it can be useful in focusing on where best to employ solutions like green infrastructure or nature-based design solutions, saying: “If communities want to protect residents from flooding, it’s crucial for them to map and understand their “hidden hydrology.”
Buried But Not Dead
More in-depth exploration of the research is found in the journal article “Buried but not dead: The impact of stream and wetland loss on flood risk in redlined neighborhoods.” (City and Environment Interactions, January 2024). The study was authored by Napieralski along with Atreyi Guin, and Catherine Sulich, and their research outlines the mapping to overlay the Home Owners’ Loan Corporation (HOLC) maps showing redlining categories, using buried streams and redlining grades to estimate flood risk. The mapping processes were interesting, including the use of historical documents and Digital Elevation Models (DEMs) to infer buried water bodies and 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.”
Using data from First Street Foundation’s Flood Factor, 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 that were integrated into risks associated with different types of impact, sorted by HOLC grade. 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.”
Figure from the article, showing flood risks by type of area “associated with inland, coastal zone, ghost streams, and ghost wetlands within redlined neighborhoods.”
This does bring up why mapping these streams and wetlands is important. They provide a basis for analysis by using other data as cross-sectional overlays, unlocking connections between impacts that may, on the surface, be unseen. The connections of this work to climate change, of which flooding is a key impact, are clear, as changes in precipitation and storm intensity make flood risks more frequent and more damaging. The authors conclude the
“[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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Note: This post was originally posted on Substack on 05/08/24 and added to the Hidden Hydrology website on 04/23/25.
The Pacific Northwest has long been one of the innovation hubs for green infrastructure solutions. Portland, Seattle, and Vancouver have been leaders for over two decades in developing innovative options to manage stormwater in urban environments, creating decentralized solutions such as green streets, rain gardens, green roofs, and permeable pavings that have now become standard solutions and spread widely to regions.
In places with high rainfall, the initial drivers for these solutions were managing stormwater and reducing combined sewer overflows (CSOs) where rain and sewage mix in pipes, which, in extreme events, overflows into waterways creating pollution issues. The importance of green infrastructure has grown to include multifaceted outcomes, helping mitigate climate impacts by reducing flooding and providing shade to reduce urban heat, and providing ‘green’ solutions over ‘grey’, increasing habitat and helping minimize biodiversity loss.
Thinking strategically about where these solutions are built is key to success. Looking beyond site-specific and one-off strategies, the goal is to provide larger overarching frameworks for how these strategies are planned to work together to achieve holistic results, and ways to plan for these interventions. “How Rainways Could Restore ‘Raincouver’” (The Tyee, August 24, 2023) highlights some of the recent work in Vancouver. What they refer to as ‘Rainways’ are the green infrastructure interventions that have been proposed by City and community groups going back to 2012 built around water in the city and ways to discover and celebrate it.
St. George Rainway illustration (City of Vancouver, The Tyee)
The St. George Rainway is another precursor to some of the work. It was studied and determined that true creek daylighting would be a challenge, due to infrastructure and costs, however, there were other ways to functionally and metaphorically restore the essence of buried creeks through green infrastructure and art. Neighbors have implemented several interventions, including street murals that follow the meandering route of the old creek.
To further visualize the potential benefits, the team here are some good before and after visuals on the site, transforming asphalt into rain gardens with pathways and plantings.
For a deep dive, the Rain City Strategy is a comprehensive document published in 2019 to celebrate water and address environmental and social challenges. The basis is green infrastructure in the city, using streets and public spaces, buildings and sites, and parks and beaches. The overall goals are water quality, resilience, and livability. This includes the management of stormwater to protect and increase water quality, facilitate infiltration, and become more adaptable to climate impacts by mitigating flooding. Beyond function, creating spaces that provide equitable access to nature and benefits to the community are inherent in solutions, assuring they aren’t just solving one problem but many.
The report includes references to the original buried and disappeared streams that existed before urbanization. These maps build on the work going back almost 50 years to research done by Sharon Proctor in her book ‘Vancouver’s Old Streams’, published in 1978 with a sweet hand-drawn version of the map below (read more about this in my 2016 post “Vancouver’s Secret Waterways”).
The execution of more formal St George Rainway design concepts is available from 2022, showing how the concepts are applied to the segments of St. George Street, with plans and sketches illuminating the proposed condition.
The holistic proposal of looking at the macro-level buried rivers as the genesis for these community interventions. The benefits of the designs are manifold, as noted in the project summary:
Reduce street flooding
Treat rainwater pollutants from roadways
Reduce combined sewer overflows into local waterways
Enhance climate resiliency
Increase biodiversity
Cool the neighbourhood during summer heat
CODA
It’s great to see this connection between hidden hydrology and innovative stormwater solutions take shape in such an intentional way. In the past, cities have looked at these buried stream routes in locating facilities and creating smaller sub-watersheds. For some background, in a presentation back in 2006 at the National ASLA conference, I did a presentation entitled “Neighborsheds for Green Infrastructure”, where I made a case for using the routing of buried streams as a framework to implement green infrastructure solutions in Portland, Oregon. I’ll dig up some of these ideas and repost them, as they may be worth revisiting, in the meantime, I mention it in part of my introductory “Ecological Inspirations” post at HH (see image below). Stay tuned for more on this.
Neighborshed Diagram from 2006 in Portland (Jason King)
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Note: This post was originally posted on Substack on 05/03/24 and added to the Hidden Hydrology website on 04/23/25.
Strong connections exist between hidden hydrology and the larger work of historical ecology, in terms of methodology and the work to piece together complete stories from fragments of disparate sources. Often the traces of historical waterways inform the larger ecological patterns of places to establish baseline conditions, and historic vegetation patterns, and begin to establish markers to document change. The overlay of indigenous occupation is an additional element, however, it is often hard to reconstruct due to a lack of physical documentation. Examples of projects successfully implementing this type of work are valuable case studies.
A recent article, “Tribal leaders and researchers have mapped the ancient ‘lost suburbs’ of Los Angeles” (Los Angeles Times, October 9, 2023) explores a successful process, highlighting work by groups using these techniques to study six village sites in the greater Los Angeles region. These “lost suburbs”, in this case, are the original settlements and villages within the LA Basin, where, as noted in the article, “…culture thrived here for thousands of years amid a landscape of oak and walnut woodlands riven with waterways teeming with steelhead trout and prowled by wolves and grizzly bears.”
Ancient routes and key village locations (LA Times)
Three tribes, the Chumash, Tataviam, and Kizh-Gabrieleño collaborated with diverse interdisciplinary academic researchers to piece together a tapestry of inhabitation, as noted in the LA Times article by one of the project leads, UCLA’s Travis Longcore: “We had to dig deep for evidence of the great society buried under our modern empire of terraced and graded slopes, rivers sheathed in concrete, industrial development, freeways and sprawl.”
These provide a trail of evidence to follow for appropriate ecological restoration and responses to climate change. Hidden hydrology is one essential key to the understanding of these ancient places. From the LA Times: “One map reveals the locations of streams, wetlands, vernal pools, and tidal flats that were buried or drastically altered to accommodate urban development.”
Comparison of development impacts on waterways (LA Times)
This is a part of the full historical ecology of the region discussed in the following section. Understanding the pre-colonization waterways allows for restoring places informed by an authentic indigenous history. As noted by Matt Vestuto, one of the collaborators from the Barbareno/Ventureno Band of Mission Indians:
“…the mapping project offers hope for a long overdue reappraisal of Native American history… Almost overnight, we were disenfranchised from the landscape — but our people are still here… now, the challenge is to restore the environment, and rebuild our nations.”
“Descriptions of the historical landscape patterns and function have led to a conclusion that this landscape and region cannot be understood without listening to the stories of Indigenous people who managed this land and thrived for thousands of years before the arrival of European settlers.”
A key part of the work is cartographic regressions, which include reconstruction of the topographic history and hydrological patterns using old maps, aerial photography, and other archival sources, like texts, drawings, place names, historical accounts, and archaeological work. The analyses look closely at trade networks, historical flora and fauna distributions, and their impact on habitat, and provide the blueprint for future restoration. As noted in the Executive Summary:
“This project is unique because a commonly shared, detailed map of the historical ecology—the flora, fauna, hydrology, and landforms, that evolved within Southern California’s Mediterranean climate over millennia and supported human populations for 9,000 years, has never been developed. Individually and cumulatively, the results of this research are vital resources to all regional and local planning efforts involving sustainability, habitat restoration, and preparing for climate change.”
Story Maps
An interactive Story Map is also worth checking out, providing a visual executive summary of the report. Focusing on the section related to Historical Water Features, the team traces stream routes in intervals, including 1896-1903 and 1924-1941, with the ability to compare, via slider, the two time periods as shown below, and highlights the radical change of regional hydrological patterns as the city developed.
The citywide mapping of vegetation types is directly related to these original historical waterways, and an interactive map, based on the Military Grid Reference System (MGRS), using a 1km grid, to provide map data in cells of potential natural vegetation (PNV). This is described in the Story Map as the “…vegetation that would develop in a particular ecological zone or environment, assuming the conditions of flora and fauna to be natural, if the action of man on the vegetation mantle stopped and in the absence of substantial alteration in present climatic conditions.”
Map of Hypothesized Potential Natural Vegetation of the Los Angeles Region (LALAH Story Map)
The connections between hidden hydrology, historical ecology, and indigenous occupation are more than just understanding the past. As the researchers point out, the ability to employ this data for solutions to loss of biodiversity, climate change impacts, and other challenges, while celebrating the cultural legacy of place, is key. There’s a wealth of information worth studying this model in more depth, to better understand the Los Angeles Basin ecology and hydrology and to refine and adapt this approach to other regions, specifically centering Indigenous stories as a key component in historical ecology work.
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Note: This post was originally posted on Substack on 05/01/24 and added to the Hidden Hydrology website on 04/23/25.
One of the cooler examples of hidden hydrology art in the past year is “Ghost Rivers”, the brainchild of designer and artist Bruce Willen of studio Public Mechanics.
Envisioned as a “…public art project & walking tour, rediscovering hidden streams and histories that run beneath our feet.” Willen uses traffic striping and signage to highlight multiple sites around the city, particularly Sumwalt Run, a buried creek that “now flows entirely through underground culverts beneath the Remington and Charles Village neighborhoods.”
The site includes some great background, including the history of the streams and their burial, along with some great illustrations of the path as it winds through
Stream burial (Baltimore DPW Archives, Ronald Parks – Ghost Rivers)
The installation itself is simple, using durable thermoplastic traffic striping in a wavy pattern that allows the line to engage with people in multiple ways and follow curbs and walks – so it is interrupting the linear flow patterns of walkers, cyclists, and driver throughout the city. This allows the eye and the curiosity to wander along these paths and connect the dots.
Images of the meandering blue path in the public realm (Ghost Rivers)
Self-guided walking tours are available and will expand as more sites are included, along with a Google map to track the route and key points. The signs are also simple, but bright and noticeable for those passersby, allowing for a bit of interactivity as they line up with the views of the meanders, and provide some background information and QR codes to scan for more engagement.
The summary statement explains the idea of connecting us with these hidden creeks.
“Below the streets of Baltimore flow dozens of lost streams. These ghost rivers still cascade from their sources, the many natural springs around the city. As the street grid sprawled outward from the harbor, these verdant waterways were buried in concrete tunnels. They now run deep beneath our rowhomes, channeled into the city’s storm sewers, hidden and mostly forgotten. You can sometimes hear their rushing waters echoing up from storm drains.”
The site also includes awesome resources for more information, history, daylighting resources, and other artistic interventions worthy of a follow-up, including a few I’ve posted about in the past and a few new ones. This is a model that is highly replicable in almost any city, using materials that are simple and evocative in unique ways to highlight those subterranean stories and make us reconsider our relationships with the hidden hydrology.
The idea is one of the most cohesive and elegant takes on the idea of revealing creeks using blue lines tracking the historical routing of the waterways. It draws upon precedents, mentioned by applying traffic coating, markers, or paint to mark the route of creeks, most similarly artist Sean Derry’s work in Indianapolis ‘Charting Pogue’s Run” and Henk Hostra’s “The Blue Road” in Drachten, The Netherlands, the proposed “Ghost Arroyos” in San Francisco. Another art-based example from Baltimore is the “Green Alley” street painting, and more loose, ephemeral versions in the St. George Rainway in Vancouver, B.C., in São Paulo, Brazil as part of the Rios a Ruas project, Stacy Levy’s Stream Sketches in New York City.
There are lots of examples of this type of project, and it is interesting to see the different ways a simple blue line can be used to engage in revealing historical layers. So let me know if you have other favorites you’ve seen.
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Note: This post was originally posted on Substack on 04/29/24 and added to the Hidden Hydrology website on 04/23/25.
The narrative of disappearance mirrors many other cities, including pollution and diseases like cholera and typhoid turning waterways from amenities to dangers. Encasement in pipes became a way to remove the sources from contact and also opened up future land for development.
Images of sewer construction in Montreal’s Saint-Pierre River in the 1930s (Archives de la Ville de Montréal – via CBC)
The article explores particular creeks in Toronto including Mud Creek, where Helen Mills, founder of Lost Rivers, gives a tour of the remnants and traces of the urban waterway. It also discusses Taddle Creek which provides one of those dramatic before-and-after visuals we all dream of when envisioning the hidden hydrology in the modern context.
Taddle Creek near Toronto University, in 1861 (uc.utoronto.ca/public domain/CBC)The same view in 2023 (Emily Chung/CBC)
The methods we used to show lost rivers are worth more exploration here, and the news interactive does a great job of using a scrolling format and some oblique aerial maps of the three cities, such as Toronto below.
The interactive aspect allows for more context for places, such as the route of Mud Creek through the Evergreen Brick Works, using a revealing overlay w/ aerial imagery with powerful effect.
Overlay of Mud Creek in the Evergreen Brick Works in Toronto (CBC)
The story similarly looks at both Montreal and Vancouver in-depth, so check out the full exploration. For some added context, I previously covered some of the Canadian cities in some depth with Vancouver’s Secret Waterways (November 2016) and Toronto’s Lost Rivers (July 2017), and also a more in-depth discussion of the great documentary Lost Rivers (November 2016).
There’s a focus on daylighting, and they include Luna Khirfan, a professor of planning at the University of Waterloo who has done extensive research on stream daylighting projects around the globe. She mentions other cities around the world that are doing work on daylighting and restoration of urban creeks, such as Zurich, Switzerland, Seoul, South Korea, Berkeley, California, and Yonkers, New York, which we will cover in more depth in the future posts.
The imagery emphasizes the constrained conditions of some of the waterways that were not buried and still exist in daylight, but have been channelized at the margins of. This image of Still Creek in Vancouver highlights the conditions of many creeks.
Even in a constrained condition, there are benefits to the visible creeks, in terms of cooling, habitat, and biophilic connections to water and nature. The story also makes the key connection between these lost rivers and contemporary climate change issues like flooding and urban heat islands. As noted:
“Climate change and urbanization are heating and flooding our cities. Restoring buried waterways — and their riverbanks — could be one answer to many problems: cooling heat islands, absorbing carbon dioxide, cleaning the air, reducing flooding and providing a habitat for wildlife and native plants.”
The story is engaging and informative, and more cities deserve that deep dive into the history and potential for exploration of hidden hydrology and potential daylighting and restoration. I also do appreciate the link to my Hidden Hydrology site for more info!
As a companion piece to the news interactive, the CBC podcast What on Earth with Laura Lynch from April 14, 2024 “Buried under cities, rivers are a climate wonder in waiting” a 30-minute exploration by Jaela Bernstien (who co-authored the previous story), and Lynch of some of these same topics in audio format, in Montreal’s Saint-Pierre, Toronto’s Mud Creek and Vancouver’s Still Creek. Through discussions with Kregg Hetherington, Amir Taleghani, and Helen Mills, it captures the beauty of hidden hydrology exploration and discovery and highlights the goals of ecosystem restoration and climate change solutions embedded in restoring lost rivers. Luna Khirfan is also part of the dialogue, discussing her work at the University of Waterloo around stream daylighting, the challenges of daylighting, and other world global cities like Zurich that have championed the idea.
Give both the article a read and the podcast a listen and let me know what you think.
Note: This post was originally posted on Substack on 04/20/24 and added to the Hidden Hydrology website on 04/20/25.
An interesting project in St. Paul, Minnesota emerged in this Star Tribune article “Work could begin soon to bring St. Paul’s Phalen Creek back to the surface,” which highlights the mix of ecological and cultural benefits of urban stream daylighting. Through a focus on both the benefits to wildlife habitat and ecosystem function and the connection of cultural heritage for native people and early immigrants to the area, it shows a rich story that is told through multiple lenses to provide solid rationale for daylighting projects.
One major idea of daylighting is visibility. As mentioned in the Star Tribune article, this is a typical case of burial of creeks for development, but like many other areas, the perceptions have shifted and the value of historical waterways are being restored. A big part of that is pointed out by Ramsey-Washington Metro district watershed project manager Paige Ahlborg, watershed project: “Another benefit is just restoring a community’s connection to the water,” Ahlborg said. “Seeing it makes it harder to do things that harm it. We still have a number of people who think that ‘if I put something down the [storm]sewer drain, it will be treated.'”
The history of places is expressed in place names. From the Capitol Region Watershed District site, some history on the current name: “Swede Hollow on the City of Saint Paul’s East Side is a historic immigrant neighborhood dating back to the 19th century. This lowland valley includes a portion of a stream from Phalen Creek to the Mississippi River. After housing was removed following the turn of the century, the city created Swede Hollow Park and placed some of the stream flow in a storm sewer pipe to complete its path to the river.”
Image of Phalen Creek burial in the 1920s. – via Minnesota Historical Society
As is the case with most places, the story and names is often told in European terms (i.e. Swede Hollow). The creek name as well comes from Edward Phalen, one of Saint Paul’s original colonists, who settled on the banks of the creek in 1838. Prior to this arrival, the history of place stretched far earlier as referenced in the Lower Phalen Creek Project, a native-led project:
“This creek served as a corridor for the Dakota people who lived here, as they made their way up the chain of lakes by canoe to White Bear Lake – one of many areas where they gathered wild rice.”
The daylighting has both ecological and cultural benefits. In the Star Tribune, Lower Phalen Creek Project Executive Direction Maggie Lorenz, who is both Dakota and Ojibwe, mentions: “[Phalen Creek] is an essential part of the community — it will bring more natural habitat and it means more opportunities for recreation and stormwater management. And, from a cultural perspective, we are really interested in restoring the land and taking care of the land according to our traditional teachings.”
While the goal is to extend daylighting all the way to the Mississippi River, one the first legs connects from Lake Phalen and Maryland Avenue as shown in this enlarged plan, highlighting the ecological benefits, including fish passage and enhanced in-stream habitat, establishment not just of the creek but adjacent floodplain wetlands to provide resilience and habitat for amphibians, and upland prairies that provide native riparian habitat supporting birds and pollinators.
“Consultants at Inter-Fluve, Inc. produced this visual to represent the proposed location, general design elements, and predicted habitat benefits of a restored stream channel of Phalen Creek at the Lake Phalen / Maryland Avenue project site.” via Lower Phalen Creek Project
A ton of additional information is at the LPCP site, including graphic summary of the project is found in a brochure that connects the dots between the cultural and ecological.
A project from artist Cristina Iglesias (see a post of some of her previous work here) again dives into the idea of hidden hydrology, this time in New York City. Entitled Landscape and Memory (referencing the title of one of my favorite books by Simon Schama), the work unearths a buried stream in Madison Square Park.
From The Architect’s Newspaper: “Manhattan is crisscrossed by streams and rivers that have since been buried but continue to flow, flooding their banks and the basements above when it rains. For Landscape and Memory, Iglesias will exhume an impression of Cedar Creek, which once flowed beneath where the park now stands today.”
From the Madison Square Park Conservancy, some more info: “Nodding to historian Simon Schama’s major 1995 volume of the same name, which surveyed the history of landscape across time and terrain, Landscape and Memory is informed by Iglesias’ research into the history of the site. For the project, Iglesias located and studied antique maps that documented the water flow beneath Madison Square Park, where the Cedar Creek and Minetta Brook once coursed for two miles before flowing into the Hudson River. With nineteenth-century industrialization, streams like the Cedar and Minetta were buried underground to create additional land for building sites, underground drains, or sewers. Through Landscape and Memory, Iglesias renders this buried history visible again, inviting viewers to contemplate centuries of transformation of urban sites that were once natural.”
Excited to hear more about this and see more images, as the sketch is a bit… sketchy. You can check out the full press release here for more info. Based on some of her previous work it will be wonderful in execution. The work will be installed from May 23, 2022, through December 4, 2022 so those in New York City go check it out and report back.
It’s more of a deep dive into some of the research, but the general thrust is that water intrusion in systems has reduced capacity, and that the intentional encasement of streams and springs in pipes reduces the capacity of infrastructure which has a significant economic, environmental and social implications for the infrastructure, as it reduced the baseflow reduces the overall effectiveness of gray infrastructure.
The typical mechanism for intrusion into pipes is related to cracks, which is assumed to be residual groundwater entering pipes in ‘dry weather’ times, where there should be no flow into the system. Groundwater intrusion should not be discounted, but there are other sources of intrusion that are typically not considered, specifically “capture of streams and springs” that impact combined systems capacity.
The figure below shows the change in baseflow and runoff response due to the intrusion of the additional water from streams and springs.
The paper continues to identify the issue, also highlighting the lack of research on this topic, and answers some fundamental questions about how this capture occurs, how to identify it, what is the magnitude and impacts, and ways to manage it. Always interested in language, one item of interest explores key terminology – culverting, extraneous water, groundwater infiltration, sewer inflows and the key element, stream and spring capture. The wordplay is compelling, with some uniquely evocative terms emerging such as parasite flow, misconnected surface waters, sewer leakage and illicit connections all telling a story of water that is in a sense, ‘out of place’.
The how and why is interesting. The most basic version is to take a free flowing stream and incorporate it into a pipe (Type A in graphic above). “Urban streams were frequently culverted and buried, especially during the period of rapid urban expansion in the 19th century.” It’s not a stretch to show that the literature confirms that “old sewers were frequently the covered channels of brooks”, as early development merely hid the streams, but didn’t generate as much additonal flow to overwhelm the piped streams. This happened with additional development and expansion of cities and impervious zones. Often the buried streams become the names for the sewers themselves, such as those specifically mentioned in the article like Garrison Creek Sewer in Toronto and Minetta Brook Sewer in New York.
The baseflow in the streams, unlike sewage, is clean, so the incorporation into pipes and transportation to wastewater treatment plants means additional strain on purification infrastructure with water that doesn’t need treatment. This relates to the original conceptual idea of the Tibbetts Brook example today, with a clear path to remove ‘clean’ water that is reducing combined capacity and overall resilience to deal with larger storms.
Additional capture happens by interception (Type B in graphic above). The most visible example is the massive interceptor sewers in London developed by Bazalgette in response to the ‘Big Stink’ in the the 1850s, acting as a divertor to sewage entering the Thames. This model was copied around the globe, with numerous examples of streams disconnected from their outfalls and no longer making it to their original destinations in the name of water quality. Portland has a large, expensive example of this called the Big Pipe. Many other cities have similar interceptor systems.
Another mode of is by directly capturing and draining spring and seeps in combined sewers, in this case through leaky pipes with cracks and joint openings. Beyond being shoddy construction, this was intentional, designed as deliberately leaky to provide drainage in areas of perched or high groundwater. The 3 types are summarized graphically above, showing variations of combined sewers and stream capture typologies.
The connection here to lost rivers is outlined in the article: “Not all streams and springs are fully captured by these modes of entry. London’s lost rivers diverted into the High, Mid and Low Level Interceptors to the WwTW, (wastewater treatment works) such as the Walbrook, Fleet, Tyburn and Westbourne, do still discharge to the River Thames during heavy storm events, where the original courses of the rivers serve as CSOs.” This is also a pattern in the United States (New York) and Asia (Tokyo) where many of the piped streams never make it to their original drainage water bodies.
The 19th Century was a historic time for burial of waterways, as the rate of urbanization outpaced the ability of natural streams to remove wastes. Thus: “Urban streams that had become open sewers were frequently culverted and buried to provide more sanitary conditions, and this concept is a popular narrative predominantly explaining the conversion of many smaller watercourses to combined sewers (type A).” Beyond the main drivers of pollution reduction and removal of the streams to create land for development, the introduction of seeps and springs provided some necessary baseflow to ‘flush’ sewers as a method of ‘self-cleansing’, and thus was in common practice in sewer design.
It is obviously difficult to identify these captured streams, as they exist under the surface and the original hydrology has been erased. This is where hidden hydrology methodology, using mapping and other primary sources to show where routes of surface flows used to run. Often these were parts of combined sewers, but in some cases the streams were just dumped into pipes. While still important, it is less impactful to combined systems and wastewater treatment facilities as they are often just draining into the same waterbodies that the original creek flowed in to.
Urban exploration is another method of finding routes of streams mentioned (which I’ve covered in depth here in many cities). Mapping of sewers and streams supplement this work, with many cities having robust sets of maps dating centuries in the past to fill in gaps of knowledge of what was there and what was replaced. More sophistical modeling can be helpful, but simple cues like place and street names and other subtle clues can also be extra data to be used to pinpoint old routes of waterways. As mentioned:
“Relevant information on lost urban watercourses helps to establish the pre-development hydrology, but the usefulness of historic maps depends strongly on spatial and temporal coverage, with many older towns and cities having altered the hydrological landscape before the first available maps. The smallest streams and springs may also not be marked on maps at certain scales, particularly intermittent and ephemeral channels.”
The ability to quantify these captured streams is equally challenging – there is adequate knowledge of the phenomenon but lacking in specific data on volumes, routes and baseflow contributions to the systems. While even knowing the levels would be helpful, measuring current flows will yield radically different results today versus pre-development conditions. When quantities can be estimated, the economic benefits can be modeled to see impacts, but this is not common. How the water is distributed is also variable and depends on unique qualities of each stream.
The major consequences are two-fold. First, the introduction of clean stream water increases the amount of water handled by treatment plants, which has larger infrastructure costs in terms of facility construction and operations. Second, loss of surface streams has impacts to habitat, less ecological connectivity, and overall less ecosystem services, including amenity value. It can even have secondary impacts on urban heat by reduction of linear corridors of riparian vegetation. While the anecdotal benefits of ‘flushing’ using the streams was developed early-on, it’s not understood if there’s actual value of these approaches.
A summary of the impacts on the industry are included:
More land and costs needed for wastewater treatment infrastructure
Additional operational costs and use of chemicals
External impacts, such as public health impacts of CSOs, impacts due to loss of ecosystem services due to diversion of local streams, and economic losses.
There’s a more detailed cast study from Zurich, Switzerland that’s worth exploring more. In summary, the authors mention the city as a pioneer through “innovative management of capture streams and springs in combined sewers,” typically through separation using daylighting. This was driven by understanding the “lost social ad environmental values of watercourses that had become culverted and had historically been used as wastewater sewers.”
The benefits to the public include amenity spaces, and also more efficient infrastructure through additional capacity. This dual benefit is key to the Stream Concept, and became codified into planning policy and laws. The dramatic reducing in streams due to urbanization is similar to other cities, with development displacing larger areas of open space and burial of streams, many of which were converted into combined sewers between 1850 and 1980 as seen in the figure below.
The transformation of streams from this point in 1980 shows the changes in approach used by Zurich in the Stream Concept. This is outline in the existing condition (1) which includes stream capture in a traditional combined sewer system, a severing of the hydrological system and piping; the first transformation (2) consisting of separation of the combined systems to removed capture streams, and eventually the final phase of the Stream Concept (3) “separating captured streams and springs into daylighted urban watercourses.”
An important aspect which reflects my approach allows for hybrids of ‘daylighting’ without and zero-sum outcome of daylight or nothing, but allow for a continuum of potential options – as I’ve discussed, between art and science (abstraction vs. pure restoration) or more specifically, interventions that can be located in a triad of artistic, design, or engineering. The street streams, per the articles:
“Naturalistic stream channels and riparian corridors are used where possible, but where space is limited, engineered “street streams” are installed. The latter may have a lower ecological potential, but nevertheless offer architectural value in urban areas.”
The two different typologies seen above show a ‘naturalistic’ approach in a more suburban location (Albrisrieder Dorfbach), versus the more urban ‘street stream’ in Zurich (Nebelbach). The street streams may mimic green infrastructure solutions like green streets as linear corridors, with the conceptual difference of being able to be hydrologically connected from source to outfall to re-connect the old stream corridor, versus merely being site specific insertions.
The article concludes that there is value in disconnecting streams and springs from combined systems (or if we could spin time back, not connecting them in the first place), with economic, environmental and social benefits. The diversion of clean, constantly flowing water out of combined systems provides capacity, and by daylighting (vs. piping) these streams, we have the additional ecosystem benefits. The need for more research is mentioned: “By using daylighted urban streams to convey the clean water baseflow, highly promising social and environmental benefits have been suggested; an independent peer-reviewed appraisal of this approach would be strongly recommended.” Since this is a 2013 article, I’m curious what additional scholarship has emerged in the last decade.
I also am intrigued by two of the US examples identified in the article were in Portland and Seattle, both of which mention combined sewers with springs running in them. Worthy of more exploration, but both of these do related to a location where a stream was buried and integrated into the pipe infrastructure of the city, which was common in many streams in both cities (for instance Ravenna Creek in Seattle, or Tanner Creek in Portland). Perhaps with the continual increasing impacts of climate change on these systems would drive another look at some daylighting to increase the resilience of the pipes to handle more capacity, while also providing habitat, amenity, recreation, and a range of other essential urban ecosystem services?
Full Citation: A.T. Broadhead, R. Horn, D.N. Lerner, Captured streams and springs in combined sewers: A review of the evidence, consequences and opportunities, Water Research, Volume 47, Issue 13, 2013, Pages 4752-4766, ISSN 0043-1354, https://doi.org/10.1016/j.watres.2013.05.020
Header Image: Figure from the article: Historic loss of Zurich’s streams (water in blue) with increasing urbanisation (grey).
I feel like I’ve been overcomplicating my explanations of the connections of climate change and hidden hydrology and Sanderson just nailed the concept in a few words. While the explanation is simple, the complex interactions between that hidden (buried) strata beneath the surface that have been erased from our urban areas and how these areas are poised to re-emerge in the urban sphere in dangerous ways as zones of flooding during extreme weather events is a topic worthy of more examination.
We have plenty of extreme events and flooding here in the Pacific Northwest to see this phenomenon play out in similar ways, causing water levels to rise in creeks or streams, or with high-precipitation rainfall that accumulates faster than it can drain in cities. Hurricanes, however, seem to be a special case in exacerbating issues just by the sheer scale and concentration of impacts in a short duration. These continual, cyclical events along the Eastern Seaboard ad Gulf Coast highlight the danger or urban flooding and as Sanderson points out, offers clear connections with the current flood events in locations of historical, now buried, waterways.
Hurricane Sandy opened many eyes to the risks. At the time there were a number of articles that caught my eye, particularly the idea that inundation and flooding at the margins were related to the idea of land filling and shoreline creation and the margins, replacing natural shorelines with hardened urban edges and bringing development out into these areas. In this June 2013 article in the Daily Mail, “How Hurricane Sandy flooded New York back to its 17th century shape as it inundated 400 years of reclaimed land.” the .
Expanded Shoreline of Manhattan from 1650-1980 – via Daily Mail
Looking at the extent of flooding in Hurricane Sandy (map below) and a number of studies on flood risk, it’s possible to do a quick mental overlay ad show the vulnerability related to the ‘made land’.
This is obviously not unique to New York City, and I’m interested in researching other places where flooding and made land has a similar correlation. In these cases, the conceptual connection started to take shape in the impacts of flooding at the edges, and how filled land can become a marker for shoreline flooding, which will inevitably be impacted more by sea-level rise in cities that have claimed1 this land from their adjacent water bodies.
The most recent events, during Hurricane Ida, Sanderson points out, go even more fine grain to individual inland areas where historic creeks or wetlands intersect with, such as Central Park (where wetlands were removed in construction of the park) and various other areas, including fatal incidents of basement flooding, in areas of where creeks, streams, wetlands and tideflats existed even up the the early 1900s.
A specific example of flash flooding in the subway in Manhattan at 28th Street and 7th Avenue (see video on Twitter post which is bonkers for both the intensity of the flooding and the utter lack of reaction from New Yorkers watching on the platform). As the article mentions the location of the flooding: “Right in the middle of a wetland clearly shown on 18th-century maps, the headwaters for The Old Wreck, a stream that fed Sunfish Pond, on the south side of Murray Hill, before reaching the sea at Kip’s Bay.”
18th Century Map showing location of wetland in area of 28th Street Station – via NY Times
The takeaway of cause and effect is summed up by Sanderson:
“The city even has a map where the extreme flooding happens, compiled from 311 reports and official observations. It is, for all intents and purposes, a map of the old streams.”
The action here is simple – avoid damage and loss of life from these events, because they are not going to stop any time soon. Increase resilience (both social and eco/hydrological) helps, and as the OpEd mentions, there are many other socio-economic factors involved that increase risk. But Sanderson looks for solutions (the old ways of knowledge) and points out “The losses are mainly the result of our inability to read the landscape where we live and conceive fully what it means to live there. We need to see the landscape in new, by which I mean old, terms.”
Where we location development must respect the hydrological history, as we’ve seen time and time again our inability to overpower nature, and ultimately the failure of forgetting what we buried. Worth a read for the article is a great explication of a terribly absent land consciousness and ethic, but at a practical level, there are some hints that allow us to connect historical ecology to solutions such as making room for water and using Nature based solutions such as wetland restoration and tree planting, many of which are continuing to take a rightful place in climate and resilience plans.
Perhaps the ending, again, for all of our complex machinations, allows us to think more simply about the solution and find opportunities for this simple action:
“Let’s let the streams run free.”
Endnotes
Maybe my own rant, but there’s a whole series of posts and discuss related to the concept of ‘reclaiming’ land from the sea, which is the common parlance in this case. I do prefer ‘claiming’ and the idea of ‘made land’, as it’s really impossible to reclaim something you never possessed in the first place.
Header image – NY Times – photo by Anthony Behar/Sipa – Associated Press
After bit of a break I’m hoping to write more frequently on all things Hidden Hydrology. For some context, in this time away I have been researching more deeply Portland’s Hidden Hydrology, delving into archives for stories of my local disappeared streams, buried creeks, and filled wetlands around the metropolitan area. I’ve also compiled a composite map of Portland spanning the 1850s through the 1900s to piece together the most complete version of the hidden hydrological layers that existed pre-settlement. I’ve kept up doing research more informally in the broader and mostly sharing on Twitter and Instagram, which are both simpler media for messaging, but also seem lacking in depth that more expansive writing can capture. While it may be true that blogging is no longer a viable medium, I feel a need to write more deeply, and more often, and more personally about my home, my history, and my places. This will hopefully lead to writing more broadly as well in journals, and culminate in my ultimate goal — to write a book (or more than one) on hidden hydrology.
A few recent thoughts, ideas that I take with me into the next journey.
Every story has a uniquely human interface and the phenomena of hidden hydrology is no different, with a variety of actors involved in the discovery, use, manipulation, destruction, protection, and restoration that are all story arcs of urban streams, wetlands and other water bodies. I have always seen the people involved in more broad strokes, as populations and groups acting against nature and natural processes, or conversely communities and coalitions being often negatively acted upon and attempting to preserve and protect systems. Rarely did I connect people to places in a meaningful way beyond faceless groups, only rarely placing individuals and their stories and essential ingredients to unlocking the true history of place.
Sketch of Indians Fishing by Willamette Falls – 1841 by Joseph Drayton (Oregon History Project)
As origin stories, the native Chinookan people have occupied and shaped the waters of Portland for centuries. There are specific narratives of leaders, like Concomly as part of the larger Chinook territory in the late 1700s and early 1800s and Kiesno (aka Cassino) who was located near Portland on Wapato Island, who was also an important figure through the early to mid 1800s , The native stories and start to take shape via early explorers, whereby they drift into settler narratives told about those indigenous people and never told by them. Thus we remember ‘discovery’ and the snapshots of what written narratives and maps were documented, but know less about the life and the interaction with many of the places in the region beyond a few major areas of significance that were spiritual centers and places of food gathering and trade. I challenged myself to weave these stories into the narratives, and although I feel more informed, I’ve barely scratched the surface, so the next steps are to engage and learn from descendants and hear stories of places that were of significance to Chinook people in the past, and those that are still resonant today.
In Seattle, I walked and wrote about Licton Springs, which explored the deep indigenous connections to place in a remnant urban stream – weaving together the long and contentious history, which was recently given protection as a landmark of cultural significance to Coast Salish people. Many of these stories need to be told, and the opportunity to connect our diverse history to water places – the water stories and human stories, continues to intrigue me.
Licton Springs (Photo by Author)
Broadening the cultural lens, I’ve written about Tanner Creek and the Chinese farmers who cultivated lands adjacent to the creek using the amazing resource by Marie Rose-Wong on early Chinese residents of Portland, documenting the erasure of the creek and the Chinese farms in tandem, both slowly disappearing from Portland in the wake of ‘progress’ that wanted neither the Chinese people, nor the messiness of flooding, steep gulches that stood in the way of a modern metropolis.
View of Chinese Farms in Tanner Creek Gulch – circa 1892 (Portland Archives)
The narratives feature places like Guild’s Lake, a contested area with a variety of actors working to destroy, displace and erase historic waterways to pave the way for development and industrialization, with little thought to the impacts ecologically and socially to these actions. As you map out the timeline of erasure for many waterways, it’s never one person or one big move, but a variety of consistent, incremental actions, driven by the need for progress and growth, that privileged the needs of few over the impacts to many. The missing piece of this is again the human dimension, the root of all of these stories were the people who occupied these places, and how they, and their actions, gave life to the unique water places in the community. And as other forces removed the waterways, how they were impacted by the places are lost. The places are not coming back, but but hopefully through the stories some idea of that experience can re-emerge and remain.
Chinese man fishing in Guild’s Lake – circa 1890 (Oregon Historical Society – OHS-bb016278)
Another significant narrative in Portland’s water history is the intersection with the African American story, told through the emergence and eventual destruction of Vanport City. There are many narratives as to the cause of the flooding and destruction of in the1940s worth exploring, and the eventual displacement and segregation that happened after the city was destroyed continues to shape the city today.
As my post documenting the amazing OPB documentary “Vanport” shows, these, too are human stories, with interviews and first person accounts of the development and occupation of this novel community, and the lead up to the destruction and displacement of larger populations of people that had lasting impacts and left an indelible mark on the racial history and social structure of Portland.
CLIMATE CONNECTIONS
While Vanport was not a result of climate change per se, this larger narrative of catastrophic flood events also provides a hint at more extreme future scenarios that intersect with my research on hidden hydrology: the connections between the lost and buried streams, wetlands, ponds and water bodies, along with made-land through filling and manipulating shorelines, and how these ultimately give clues to and exacerbate our present impacts related to climate change.
Stories in the mainstream media are reinforcing these connections, and through recent research, and continues to gain prominence and momentum as a dimensions of climate change evolve and the impacts are played out in communities more frequently and in more extreme forms.
There are a number of drivers for the ‘creative destruction’ of water systems in cities. Making land for development by piping creeks, filling gulches, ponds, wetlands and shorelines to make developable land offers the chance to grow and continue to build. Much of this was also an element of the modern safety movement that was concerned with life and property damage from flooding creeks, and the related sanitary movement was driven by public health concerns, often by removing access to polluted waterways. In short term and in earlier times, these efforts may have seemed good approaches but come with some unfortunate baggage in loss of ecosystem function, and lack of resilience.
Flooding is obviously not a new thing, and is not always the result of removal of waterways not of climate change. However it is not difficult to make general connections that flooding often follows the historical shape of water in cities, and that removal, filling, and piping of creeks, streams, wetlands and ponds has lasting impacts to the hydrology and that the impacts will be more evident as climate change raises sea levels, increases extreme precipitation and storms, and increases urban heat.
A recent NY Times editorial by Eric Sanderson makes this case, unpacking impacts of recent extreme weather and hurricanes and tracing that to lost streams that wove through New York City. The simple statement of “Water will go where water has always gone.” sums up the phenomenon, while giving us an interesting new (old?) methodology for predicting impacts by using historical hydrological systems in new ways. Beyond that in the past year, my Twitter feed is filled with stories of flooding in Europe, UK, and around the US, a global climate change induced impact all traced back to the link between historical waterways and current, human-caused climate change. Lots more on this topic to come.
EVOLUTION
As I researched more from the archives of local newspapers and uncovered more unique, human stories, the narratives became less about places and the lost waterways, but how these created a tableau of life. Rarely were stories these idyllic and utopian, but painted a picture of daily life and the struggle to build a city carved out of the forest at the confluence of two rivers. Often they were narratives of greed, racism, and exploitation, focusing on power and money which were allowed to run rampant in a time of very little environmental policy and awareness of impacts.
The water stories become stories of native people who developed thriving communities that were in a short span of time decimated by disease, violence and displacement from their lands and waters. The stories of Chinese farmers who lived on the margins of gulches and ponds in Portland, who contributed to the building of the community and were rewarded with racism and erasure from their places of productivity and community. The devastation of a flooded African American community of Vanport left ship workers and their families, engaged in supporting the war effort while building a life in Portland left many without a place live and led to a continuing and marginalization that continues today.
These historical water stories connect people to place and add a human dimension to an ecological history. When woven together with more contemporary climate stories, it also provide a solid foundation for why this work matters in design and planning for the future. It is far from a nostalgic looking back of what’s lost, but rather an opportunity to think about lessons learned related to how we can live and thrive together while growing a diverse community. It is also a blueprint for action on climate resilience, a future-focused approach to planning for urban heat, flooding, and other key resilience measures to make our communities more livable. Call the preliminary phases of this project a good information gathering, understanding what hidden hydrology is. The evolution becomes how to use this information to shape our communities in positive ways. Look forward to exploring and continuing to evolve.
