Prior to major urban expansion during the 19th and 20th centuries, many smaller rivers and streams often ran through some of the larger towns and urban places. These freshwater bodies sometimes formed vital links and provided freshwater to communities.
As urbanism grew, however, many of these rivers were paved over and have become subterranean rivers that still run but are less visible.
In other regions, particularly karstic areas with underground cave systems, underground rivers and waterways are also naturally found. All of these water systems can form vital natural systems for ecosystems and help prevent against flooding.
London’s Subterranean Rivers
Some of the best examples of small and even medium size rivers that have become subterranean are found in London.
The names of the rivers often survive in street names or place names. For example, Fleet Street in central London has been known as a street populated by different press and newspaper firms. The street is named after the River Fleet, which use to flow into the Thames and has since been completed covered over.
Parts of the river are visible in places, but most of the river runs underground.
Many older maps show these paved over rivers, which has helped keep memory of where some of these rivers once ran.
Overall, there are about 21 small to medium sized rivers, and many other even smaller streams, that are classified as subterranean rivers today in London. Some are visible as part of the city’s wider sewer system or culverts, where they have also become part of the system moving wastewater since the 19th century.
New York City’s Subterranean Rivers
In New York City, a similar story emerges, where dozens of streams have been covered over the last two hundred years. This includes the Minetta Brook in Manhattan, Sunswick Creek in Queens, and the Wallabout Brook in Brooklyn.
Interestingly, engineers still often consult maps from the 19th century for New York, such as the Viele Map from 1874, as buildings are rebuilt or modified, where these places face flooding and other water-related damage issues.
The streams effectively still run and this forces careful planning when new buildings are placed. In cases, these steams can even be found inside buildings, such as in basements, where they go through the concrete. Some buildings have even created small channels for steams to run through them.
Hazards of Paving Over Rivers
While some of these streams and rivers are curiosities or remain alive in memory through street and place names, there is a more serious consequence of building over rivers or streams.
As flooding becomes a more significant problem for cities, particularly as climate change intensities rainfall, subterranean waterways also become hazardous for cities. Rivers that use to absorb excess rain or wash away rainfall are now more constrained but still to a degree running underground.
As rainfall intensifies, with more concrete around that does not absorb a lot of water, then normally quiet subterranean rivers can become inundated and underground structures such as subways or basements flood.
Even at the street level, such flooding can become evident. In fact, it can be deadly for major urban cities such as Guangzhou in China, where this problem has been well documented.
Mapping Subterranean Rivers
GIS specialists have begun mapping underground rivers and channels to get a better sense of flood risks within cities and planners could use such maps to developed urban reservoirs to hold excess water during times of greater rainfall.
Underground rivers and channels are not just potential hazardous but they can also be important sources of water for lakes and residents along these subterranean features. This is the case for such systems that are naturally occurring rather than having become subterranean due to human activity.
Mapping these waterways using electrical resistivity, for instance, is important to understand how these subterranean water sources can be best preserved.
This is the case in Kenya’s Kabatini Area, where the Kenyan Rift Valley system has many river channels that form vital water sources for surface features such as lakes and people using these sources. Geophysical techniques enable the identification and differentiation of water relative to background material such as rocks and sediments.
Conservation of Subterranean Rivers
Increasingly, conservation is emerging as an important goal for natural subterranean rivers and features.
Currently, the biggest example of an area with subterranean rivers that is being purposely preserved as a national park can be found in Puerto Princesa in the Phillipines. The area forms an important riverine region with an 8.2 km underground river that flows into the ocean. Biodiversity along the river and above ground greatly depends on the river.
In urban systems, there has been efforts to increase protection and even restoration of lost rivers. For instance, the creation of underground tunnels or using above surface drainages has allowed some rivers to return, at least in some state. There are also efforts to use green roofing and removing concrete areas to improve drainage areas within cities.
The European Centre for River Restoration (ECRR) is an example of an initiative that is large-scale and focused on Europe, with the effort supporting short-term and longer-term sustainability efforts, that are aimed at restoring rivers in urban zones.
While all underground rivers or streams cannot be easily resurrected, revitalisation of some of these waterways along the courses of their natural channels could help cities reduce flooding and even bring some wildlife back.
Some natural-based solutions in urban zones, such as creating green spaces and parks along formerly paved areas, could be part of the solution. For many other lost rivers and streams, creating channels for water to more easily move might be a better solution, which can also relieve potential flooding.
Video: Timelapse showing the revealing of the River Roch
The River Rock was covered in the 19th century beneath the Rochdale town center in the United Kingdom. The historical medieval bridge and sections of the river were uncovered in 2016.
This video shows a time-lapse of part of the excavation process for revealing this subterranean river.
Looking at our major cities, it is clear that hundreds and thousands of our natural rivers and streams have been paved over during the last two hundred years of urbanism.
These have become, in many cases, subterranean rivers and streams that can still be found today in some flowing state, even if they are not always visible. Some of these systems are better known, where old maps exist, while the use of geophysical methods such as resistivity can help map some of these lost rivers not only in our urban places but also in areas where subterranean rivers naturally exist.
It is clear that underground water systems play a vital role in recharge of lakes as well as providing vital water sources. In recent years, conservation efforts have been slowly developing to help restore, in places, old rivers and streams to help improve against flooding and improve wildlife.
 For more on London’s underground rivers, see: Bolton, T. London’s Lost Rivers: A Walker’s Guide; Strange Attractor: Devizes, 2014; ISBN 978-1-907222-03-0.
 For an example of how streams running under New York are still found and sometimes emerge in buildings, see: http://www.scoutingny.com/stumbling-upon-an-underground-river-in-manhattan/.
 For more on Guangzhou and flooding problems encountered, see: Lyu, H.-M.; Wang, G.-F.; Shen, J.; Lu, L.-H.; Wang, G.-Q. Analysis and GIS Mapping of Flooding Hazards on 10 May 2016, Guangzhou, China. Water 2016, 8, 447, doi:10.3390/w8100447.
 For more on mapping subterranean water channels in Kenya using resistivity, see: K. Waswa, A. Application of Electrical Resistivity Method in Mapping Underground River Channels: A Case Study of Kabatini Area in the Kenyan Rift Valley. ujg 2019, 7, 1–14, doi:10.13189/ujg.2019.070101.
 For more on Puerto Priccesa and its underground river, see: https://undergroundriver.puertoprincesa.ph/.
 For more on the Europan Centre for River Restoration, see: https://www.ecrr.org/.