The idea of Detroitโs 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 โredliningโ maps. For a little background, the Home Ownersโ 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 โhazardousโ or โhigh-riskโ 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 โโฆ to determine whether a history of waterway burial and/or redlining influenced the overall flood risk of communities today.โ 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:
โFlood risk is very intricately linked to history, and by ignoring history we may be missing some clues that help us move forward.โ
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: โIf communities want to protect residents from flooding, itโs crucial for them to map and understand their โhidden hydrology.โ
Buried But Not Dead
More in-depth exploration of the research is found in the journal article โBuried but not dead: The impact of stream and wetland loss on flood risk in redlined neighborhoods.โ (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 Ownersโ 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:
โAlthough 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.โ
Using data from First Street Foundationโs 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: โFlood 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.โ
Figure from the article, showing flood risks by type of area โassociated with inland, coastal zone, ghost streams, and ghost wetlands within redlined neighborhoods.โ
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
โ[The]โฆrole 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 โhidden hydrologyโ may play in increasing flood risk.โ
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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 โgreenโ solutions over โgreyโ, 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. โHow Rainways Could Restore โRaincouverโโ (The Tyee, August 24, 2023) highlights some of the recent work in Vancouver. What they refer to as โRainwaysโ 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 arenโt 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 โVancouverโs Old Streamsโ, published in 1978 with a sweet hand-drawn version of the map below (read more about this in my 2016 post โVancouverโs Secret Waterwaysโ).
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
Itโs 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 โNeighborsheds for Green Infrastructureโ, where I made a case for using the routing of buried streams as a framework to implement green infrastructure solutions in Portland, Oregon. Iโll 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 โEcological Inspirationsโ 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 โlost suburbsโ 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 โlost suburbsโ, 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-Gabrieleรฑo 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: โWe 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.โ
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 โ but our people are still here… now, the challenge is to restore the environment, and rebuild our nations.โ
โDescriptions 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.โ
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:
โThis project is unique because a commonly shared, detailed map of the historical ecologyโthe flora, fauna, hydrology, and landforms, that evolved within Southern Californiaโs 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.โ
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 โโฆvegetation 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.โ
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. Thereโs 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.
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 Montrealโs Saint-Pierre River in the 1930s (Archives de la Ville de Montrรฉal – 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 Vancouverโs Secret Waterways (November 2016) and Torontoโs Lost Rivers (July 2017), and also a more in-depth discussion of the great documentary Lost Rivers (November 2016).
Thereโs 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:
โClimate change and urbanization are heating and flooding our cities. Restoring buried waterways โ and their riverbanks โ 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.โ
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 waitingโ 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 Montrealโs Saint-Pierre, Torontoโs Mud Creek and Vancouverโs 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.
The article โTracing Tokyoโs Hidden Riversโ (The Japan Times, March 2024) was a fascinating dive into hidden hydrology mapping and urban exploration through the lens of Japanese culture and added a new term to my lexicon. The concept of ankyo, ๆๆธ . which at a basic level translates in English to something akin to โculvertโ, โconduitโ or โsubterranean drainโ. These features have been removed from the city’s original landscape, yet still reveal themselves in numerous ways. This is the starting point for Hideo Takayama and Nama Yoshimura, who together started โAnkyo Maniacsโ, a group focused on exploring these urban remnants of buried and hidden streams in the City of Tokyo.
Tours of the ankyo reveal waterways flowing under manholes (The Japan Times)
The explorers rely on what they call โankyo signsโ, which include a wide range of markers that help clue us into the hidden hydrology, including place names, objects, and drains (such as shown above) which allow the visual and auditory connections to flowing water. There are also urban remnants such as barriers and old bridges that were previously in place to protect from open waterways but were never removed, or prevent access to areas that have been covered over. More obvious are places focusing on water, including baths, pools, and fishing ponds. The Ankyo Maniacs and others have refocused attention on these liminal spaces, as mentioned in the article:
โWhile they may be out of our sight, Takayama says water still flows through many ankyo, while others have become part of local drainage systems. โItโs as if theyโre telling us, โWeโre still here,โโ he says. โBy getting to know them, we can appreciate the past dignity of these rivers.โ
The basis for the exploration relies on several maps and the history of Tokyo spans many years. The Tokyo Ankyo Sanpo (Tokyo Ankyo Stroll) map, edited by So Honda, provides the go-to for locals exploring the city with ankyo and other features mapped in detail. Another more modern resource is the Tokyo Jisou, or Time Layer Maps, available as an iPhone and iPad app, which is a map viewer that shows maps of the city at different periods, spanning the Meiji to Heisei Eras from the 1800s to present time.
Images from the Tokyo Jisou Maps – by the Japan Map Center (App Store)
Beyond the specifics of mapping and exploration, the language of hidden hydrology is also fascinating, the Japanese term โankyoโ providing a case study of the hidden poetry of the terms. At a basic level, ankyo describes these places in practical terms, as drains and culverts that work to convey water underground. When you look at the underlying meaning of the characters, it hints at ideas like โdarkness, shade, disappearanceโ which allude to the more mysterious nature of the network of underground features that compel us to explore. The Tokyo Ankyo Sanpo map mentioned previously also includes the opposite features โkaikyoโ ๆตทๅณก, which are the still-visible open channels, evoking lighter ideas like โcheerful, pleasant, and agreeableโ.
An example of one of the tours is found on the Experience Suginami Tokyo site, providing self-guided instructions in the area of Ogikubo Station following the route of the former Momozonogawa River and portions of the Zenpukujigawa River, including โankyo signsโ such as alleys and paths that act as covers to the buried streams, curving walkways mimicking the previous channels, and other hints at the hidden histories underneath.
The heart of the process isnโt just about the learning or processing of information, but about the experience. The prompt by the explorers: โDonโt Think. Walk and Feel!โ is imbued with ideas about slow time, and the benefits of connecting to places more deliberately. It also connects to larger ideas about experiencing places, observing and connecting to the signs and features of the urban landscape, expressed in the Japanese concept of โwabi-sabiโ, allowing appreciation of nature, along the way.
The language barrier does limit my full understanding of the content, (including what seems like some great publications) so if any Japanese speakers have more to add, I would love to hear it. For some bonus content, this short video with Takayama and Yoshimura in Tokyo outlines their work exploring the ankyo.
The idea of revealing the locations of hidden places is compelling for all who study hidden hydrology in its many forms. As summed up in the video: โAnkyo hunters say they enjoy the idea that at any moment you could be standing over a piece of forgotten Tokyo.โ
Note: This post was originally posted on Substack on 04/18/24 and added to the Hidden Hydrology website on 04/18/25.
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 Paulโs 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 โ 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,ย flooding their banks and the basements aboveย when it rains. Forย 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 Schamaโs major 1995 volume of the same name, which surveyed the history of landscape across time and terrain,ย Landscape and Memoryย is informed by Iglesiasโ 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. Throughย 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. Londonโs 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 โstreet streamsโ 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 Zurichโs streams (water in blue) with increasing urbanisation (grey).
The recent article in the New York times on the daylighting project at Tibbetts Creek reminded me, based on some of the comments, of the poem by Robert Frost called “A Brook in the City”. I knew of the poem, but hadn’t really made the connection to hidden hydrology, but the tones of industrialization that . Some analysis of the poem explains the context, as the poem “wasย written somewhat in earlyย 1920 when history was witnessing Industrial Revolution and urbanization. It was at that time man became an evil and the outcome was the devastation and extinction of nature.”
West Running Brook No. 3 – J.J. Lankes (via Book Porn Club) – one of the woodcuts of another Frost collection of poems ‘West Running Brook’.
The brook becomes the symbol for that devastation, and the domination of nature the culprit: “…because of manโs modernization the brook which was a symbol of force is now nothing more then a weak and meek sewer. At night it still flows. Aย time would comeย when people would forget that there was a brook which existed. It would only exist on maps. The poet wonders if man could ever ever understand his mistake.”
An interesting piece of poetry that hits at the root of loss, memory, and the essence of hidden hydrology. Sad and beautiful, be still resonant a century after it was written, and somewhat poignant to consider as we daylight and restore the brooks… reversal of some of that old wounds made right. Enjoy.
A Brook in the City – Robert Frost
The farmhouse lingers, though averse to square With the new city street it has to wear A number in. But what about the brook That held the house as in an elbow-crook? I ask as one who knew the brook, its strength And impulse, having dipped a finger length And made it leap my knuckle, having tossed A flower to try its currents where they crossed. The meadow grass could be cemented down From growing under pavements of a town; The apple trees be sent to hearth-stone flame. Is water wood to serve a brook the same? How else dispose of an immortal force No longer needed? Staunch it at its source With cinder loads dumped down? The brook was thrown Deep in a sewer dungeon under stone In fetid darkness still to live and runโ And all for nothing it had ever done Except forget to go in fear perhaps. No one would know except for ancient maps That such a brook ran water. But I wonder If from its being kept forever under, The thoughts may not have risen that so keep This new-built city from both work and sleep.
Header image – excerpt of woodcut from J.J. Lankes from another Frost collection of poem, “West Running Brook” – via Book Porn Club
The connections between climate and hidden hydrology is a continuing theme, and inevitably will result in more examples that can be documented making the connections between present and future impacts and historical ecological systems. Each of these has a specific context, which influences the extent of impacts (urban/rural) and the hydrological dynamics (lakes, rivers, shorelines). The recent flooding in November of this year in the town of Abbotsford, which lies near the border of Washington State and British Columbia is one recent example. The connection was made via Twitter by @tornadodc (Lisa Genialle), who posted the following image of flooded highway overpass with the quote “Anyone who knows their local Fraser valley history, this used to be a lake back in the day. Before it was drained to make way for settler farming.”
I had little reference for this particular region or the Sumas Lake specifically, however was supplied with more context via the subsequent thread of responses, many of which yielded Chad Reimer’s 2018 book “Before We Lost the Lake” which explores the ‘biography’ of the lake and its ‘natural and human history’. This provided some much-needed context for what existed and how the flooding takes the shape of this lost lake.
Reimer outlines a similar story found in many locations, a waterway that had been a vital and ecological benefit to the surrounding environment and a resource to milennial of indigenous people, and was summarily ‘reclaimed’ for farmland through drainage, canalization and pumping in 1924. From the review in the Chilliwack Progress: “For thousands of years, Sumas Lake sat near the centre of local culture and life. Then, nearly 100 years ago, engineers drained Sumas Lake, built a canal to harness the Vedder River, and, in the process, radically transformed the area.” A big missing piece of the narrative also covered by Reimer’s book is the displacement of the indigenous people, who have sought compensation for the lost cultural resource, both as a place of hunting, fishing, and gathering that was eliminated when the lake was filled.
Beyond the Sumas First Nation people, the lake is forgotten by most, or at best a historical footnote. As mentioned on the publisher’s site: “Today, few people are aware that Sumas Lake ever existed. The only reminder is a plaque erected on the old lakeshore, at a rest-stop along the Trans-Canada Highway just east of Whatcom Road, on the historic trail blazed to BCโs gold fields. Yet for millenniums, Sumas Lake was a dynamic, integral part of the regionโs natural and human landscape.”
The narrative that hidden hydrology is gone but not forgotten is both a cultural phenomenon (in histories and place names for instance), and ecological one (the loss of ecosystem services by removal of function and resilience), and a hydrological one (systems impacted yet still wanting to function and flow as they once did). The extreme storms exacerbated by climate change take shape in these old patterns. For Sumas Lake, a series of maps show the devolution and the impact of the most recent flooding. The first from Wikipedia is an animation of the lakes removal over the years between 1827, the filling in 1924 and the development through the 1940s. It includes the extent of devastating 1894 flood, which was the impetus for the eventual drainage.
From the Fraser Valley News, an undated map (pre-1924) of the lake shows the original extent of the historic shoreline (referenced here as Lake Sumass) which covered between 9,000 and 11,000 acres inside the valley.
The area had been developed over time, starting with transformation into agricultural fields and while mostly rural productive lands, have also since been developed with some other residential and commericial uses. The map below from an extensive analysis of the flooding by the Tyee as part of an article “Mapping the Flood in Abbotsford“, show the original lake, and also showing the dashed line outlining the extent of the 1894 flood within the confines of the valley as well.
The extent of flooding in 2021 came from the Nooksack River and breached the Sumas River dike. The amount of water overwhelmed the series of pumps, which are able to move 250,000 gallons per minute of water, which became unable to keep up with the sheer amount of flooding and the area was quickly inundated, cutting off roadways and stranding people and livestock. The shape of this water corresponds to the former lake bed, with significant depths estimated in a 2020 study to map worst-case flood scenarios, proved to be a hint at what impacts were to come in an extreme event.
The actual flooding is not as bad as the map scenarios above, but did expand into many areas outlined in the former lake bed, the deepest sections potentially inundating more than 3 meters. The post from the Fraser Valley Current shows many of the scenes of flooding near Abbotsford (seen below) which cut off some routes of evacuation, with some people rescued via helicopter. Sparsely populated, the impacts were severe but could have been much worse in a zone of higher population density.
The impacts to property and life are not to be dismissed and my goal here was not to extensively cover the events at Sumas Lake. The bigger picture was that we do need to make the connection between areas where the historical draining and filling waterbodies for progress and development (and often, ironically for flood protection) does have the potential to give hints at the future impacts of extreme events such as the flooding at Sumas Lake, beyond the loss of habitat and other ecosystem services and the lost resource for indigenous people. The photo below, circa 1900 shows the original lake from Daily Hive (which also is a great overview of the lake’s history), which looks remarkably similar to the photo above of flooding here in 2021 (with another major flood in 1990).
The case in point, that water will inevitably ‘find the level’ and create massive impacts, the memory recall I used to outline this post, and this has implications for life and property with real economic and social impacts. As noted in the Daily Hive story: “A 2016 study by the Fraser Basin Council on the Lower Mainlandโs flood management strategy estimated that a repeat of the severity of the 1894 flood would currently cost about $23 billion in damages, including $9 billion in losses to residential, commercial, public, and institutional buildings; $7.7 billion in interrupted cargo shipments; $4.6 billion in infrastructure losses; and $1.6 billion in agricultural losses.”
It’s probably too early to tell how large of an impacts was absorbed by the events fall, but history can instruct us in perhaps knowing the location of impacts and using this as a guide for prevention. This is a more rural example, and I’m working on similar urban examples, which, as climate change continues to impact rainfall and other weather events, will be more and more useful in helping us understand, and plan, for what’s next.
