Stream daylighting refers to the practice of bringing formerly buried or culverted streams back to the surface. The term may also be used to refer to the decommissioning of storm sewer drains and creating new surface channels or bioswales for managing stormwater.
Restoring streams to the surface and creating healthy riparian communities along them creates opportunities for restored wildlife habitat, recreation, groundwater infiltration and greenhouse gas sequestration.
Developing an urban watershed plan can help guide the protection of perennial and seasonal (ephemeral) streams. Elements of an urban watershed plan can be enshrined in municipal bylaws, design guidelines and design standards.
Residents, businesses and industries can be made aware of the benefits of urban stream daylighting through public education and awareness campaigns.
As a preventative measure, municipalities should develop bylaws that prevent the burying of streams and storm drains, where possible. Some streams dry up in urban areas because of human impacts on the surrounding hydrology and runoff systems. One option for mitigating this effect is to divert stormwater runoff to constructed wetlands (link to stormwater wetlands) and then use filtered outflow from these systems to restore flow into streams.
Restored streams do not necessarily have to follow their original course, although restoration efforts may be more successful if some semblance of the original topography remains. In highly developed areas, daylighted streams can be directed to run through constructed channels such as laneways, pedestrian streets, schoolyards, city parks and vacant lots where possible.
Municipalities should try to ensure that daylighted segments of streams are connected to adjacent water bodies to allow for migration of aquatic organisms and wildlife movement.
It may not always be practical to restore the stream to an earthen bottom and fully vegetated banks, although this is the ideal.
There are several technical considerations when undertaking a stream daylighting project. These include the design, performance, water quality objectives, pollutant load and construction logistics. Detailed engineering and hydrology assessments need to be conducted to determine the appropriate configuration of the daylighted stream given its projected water volume, flow rate and contributing watershed area.
Institutional considerations include ownership, maintenance, liability, permits and leadership.
Local residents may have concerns about the appearance of the restored stream and possible risks to public safety from having newly created open water. These can be mitigated through public education and awareness campaigns on the benefits of stream daylighting. The process of public engagement and participation in restoring a buried stream can foster a strong sense of community and civic spirit. Involving residents, businesses and government and gaining their support for the project is essential to its success.
The Business Side
Easier to be proactive than reactive. It is more cost-effective to avoid burying streams when possible and to use surface drainage systems rather than underground storm sewer systems. The economic costs of undertaking a stream daylighting project can be significant. Often the project is located in a highly urbanized area where dense development and high land costs restrict the amount of land that can be acquired for restored stream courses.
Leveraging funds. Costs for stream daylighting can be managed by leveraging in-kind support and donations and by engaging community volunteer support.
Opportunity for daylighting during repairs and upgrades. Costs will be higher if the stream has been culverted through a combined sewer overflow pipe (i.e., requiring the municipality to create a dedicated sewer pipe while bringing the stormwater to the surface). In many cases, however, stream daylighting can be conducted concurrently with storm drain infrastructure upgrades or when repairs are needed or when culverts have collapsed. In this case, the costs of daylighting may be comparable to or slightly more than replacing or repairing an underground conveyance system. Furthermore, many municipalities are in the process of replacing combined sewer overflow (CSO) conveyance systems with dedicated stormwater and sewer conveyance systems. These upgrades provide a cost-effective opportunity to replace CSO systems with a dedicated sewer pipe and a daylighted storm drain.
Extend storm sewer and CSO systems. In cases where stormwater and sewer water are together in combined sewer overflow systems (CSO), daylighting can help to extend the existing capacity of these systems and reduce the chances that heavy rainfall events will cause the sewer overflow to enter rivers.
Replacing deteriorating culverts with an open drainage system allows the system to be more easily monitored and repaired if damaged.
Despite higher capital costs, daylighting buried streams or storm drains provides numerous environmental benefits and ecosystem services as detailed in the following section.
The Nature Side
Potential for improved water quality in receiving water bodies. Daylighting creeks and restoring their streambank (riparian) vegetation and floodplains (where space permits) supports biological water filtration. Vegetation along the streambank and the floodplain slows the surface water, thereby allowing sediments to settle out. Riparian plants also take up nutrients (e.g., fertilizer in runoff) from the water, potentially reducing problems with excessive algae in the receiving water and eutrophication. Exposure to the air, ultraviolet radiation, microbial activity and soils also helps to transform, bind or otherwise treat contaminants. The reduced stream flow velocity also protects channels and downstream water bodies from bank erosion. This configuration can actually provide greater hydraulic capacity compared to confining water to concrete pipe systems, providing relief from “choke points” and flooding problems caused by under-capacity culverts.
Wildlife habitat. Restoring streams and riparian vegetation in urban areas can provide valuable wildlife habitat to an otherwise habitat-deficient landscape. When streams and adjacent habitat areas are of sufficient size and quality they can also be effective corridors for wildlife movement through cities. Reconnecting streams with major rivers allows for upstream migration of fish to spawning habitat as well as downstream fish passage.
Infiltration. Removing storm drains and streams from the confines of concrete allows for groundwater infiltration, restoration of aquifers and subsoil irrigation in urban areas.
Daylighting streams and restoring riparian zone vegetation also increases biodiversity and carbon sequestration.
The Community Side
Restored urban watercourses can support new recreation areas and provide opportunities for residents to interact with nature, including wildlife and bird viewing and fishing. When flowing through or close to school grounds or university campuses, daylighted streams provide outdoor “laboratories” for students to engage in hands-on learning about aquatic and riparian ecosystems.
Daylighting streams brings more nature to communities and this has a positive impact on mental, physical and social health in the surrounding area.
This example of NBS can help revitalize and beautify neighbourhoods and increase public engagement. The presence of a restored stream and associated green space can also boost the property value of adjacent properties and surrounding neighbourhoods.
 &  Rocky Mountain Institute. 2000. Daylighting: New Life for Buried Streams. Rocky Mountain Institute.
Primeau, S., Bell, M., Riopel, M., Ewaschuk, E., & Doell, D. 2009. Green Communities Guide: Tools to Help Restore Ecological Processes in Alberta’s Built Environments. Land Stewardship Centre of Canada.
Rocky Mountain Institute. 2000. Daylighting: New Life for Buried Streams. Rocky Mountain Institute. Available online at: https://rmi.org/insight/daylighting-new-life-for-buried-streams/.