Buried Streams Research Articles

Buried but not dead: The impact of stream and wetland loss on flood risk in redlined neighborhoods

The United States government sponsored the Home Owners’ Loan Corporation (HOLC) in the 1930s to assess and grade neighborhoods based on perceived financial risk. The grades were influenced by the presence of minority racial groups, immigrants, and residents with lower socioeconomic statuses and, even though the practice was eventually outlawed, the impact on low income and underrepresented minorities is still prevalent today. This study was designed to assess spatial patterns and intensity of flood risk to (a) HOLC grade, (b) proximity to coastal zones, (c) intensity of vegetative cover, and (d) relationship to buried (ghost) streams and wetlands to determine which variable has the most impact on flood risk. Flood risk data, acquired from First Street Foundation’s Flood Factor dataset, was summarized by HOLC grade, and ghost streams and wetlands were digitized from historical maps and aggregated by HOLC grade. The results show flood risk is higher in C and D graded neighborhoods, compared to A and B. Regardless of HOLC grade, neighborhoods near the Detroit River and Lake St. Claire have 10 times higher flood risk than inland neighborhoods. Interestingly, B-graded neighborhoods exhibit minimal impact from buried rivers and wetlands, but that risk increases substantially if there is a history of stream or wetland burial within a D graded neighborhood. 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.

Urban Stream Corridors and Forest Patches—The Connections: A Case Study of Bloomington, IN

Streams and forests are ecosystems connected through hydrology, but few studies have looked at the connectivity between streams and forests in the context of urban development. City-made decisions affect connections between streams and forests by isolating both ecosystems. Streams are often channelized or buried to increase potential development areas. Forests often become fragmented and may be removed unless protected. Historical choices in land usage affect the sites and sizes of current urban streams, forests, and development. This affects the distribution of impervious surfaces, which separates streams from forests. Despite these barriers to stream/forest interactions, cities can experience stream/forest connectivity. Seven Bloomington watersheds are ranked on their proportions of buried streams, channelized streams, forested hydrology, forested streams, urban forest patch cover, and impervious surface cover, along with the historical presence of urbanization. Watersheds demonstrate stream/forest connectivity, with five watersheds containing 50% or greater forested stream segments. Bloomington canopy cover reduces stormwater runoff by approximately 127 kiloliters per year. These forested areas reduce flooding, reduce nutrient loading, and reduce stream conditions associated with urban stream syndrome. Understanding urban stream/forest connectivity can improve green infrastructure design and green space design, which improve urban resilience and better connect residents to the environment.

Back to the surface – Daylighting urban streams in a Global North–South comparison

Many urban streams have vanished from the surface as a collateral effect of urban growth. Often, these buried streams have been forgotten, and only street names remind us of their existence. Reasons for stream burial include the gain of space for road or house construction or the use of stream water to transport wastewater. Today, restoration efforts to bring back fully canalized streams to the surface and to restore their stream bed (so-called daylighting) are being increasingly integrated into urban blue-green space planning, recognizing the high ecological and social value of urban streams, especially to support resilience against climate change impacts in cities. In this paper, we briefly revise the impacts of stream burial, present a series of case studies of daylighting from Europe (France, Switzerland, and Germany), and compare them with case studies from Asia (China, India, Taiwan). We found that high real estate prices, limited buffer riparian zone and resistance by the inhabitants were the greatest obstacles to stream daylighting projects. In contrast, economic gains from separating wastewater from rainwater and revival of cultural linkages with water were the strongest drivers to restore these streams. We then present methods on how to identify buried streams as candidates for daylighting and deliver criteria to select the most promising candidates. Acknowledging that each restoration project requires to be adapted to the local biophysical and local setting, we deliver a preliminary decision support system and a guideline for identifying the best candidate streams for daylighting projects, including the arguments in favor of restoration, the caveats, the social processes of decision-making, and perspectives for the integration of stream daylighting into urban climate change mitigation and adaptation concepts, in a Global North-South comparison.

Event scale hydrograph responses highlight impacts of widespread stream burial and urban infrastructure failures

AbstractFast hydrologic responses to storms in urban areas are often attributed to high percentages of impervious surfaces; however, another factor affecting urban storm response is channel burial. No previous studies have documented storm event responses in buried streams despite how common stream burial is in urban areas, with some US cities having over 75% of all headwater channels buried. Understanding event dynamics is particularly important as climate change predictions suggest an increase in frequency of high intensity storms and urban flooding. This study used 15‐min precipitation and discharge data over a period of 6.5 years to categorize storm event responses in Nine Mile Run, an urban watershed in Pittsburgh, Pennsylvania where 98% of all channels are buried. Extensive stream burial led to lower watershed retention capacity and resulted in faster storm event responses relative to other urban streams with comparable imperviousness. Additionally, urban water subsidies in the form of sewer overflows, hydrant flushing, or water line breaks can have measurable contributions to flow event responses and result in seemingly unfeasible runoff ratios. This study demonstrates novel watershed runoff responses in systems dominated by subsurface infrastructure, which play a key role in urban water balance. Additionally, this study highlights the fact that stream restoration is not a universal solution to urban stream flashiness because downstream restoration cannot resolve the impacts of upstream burial.

Urban buried streams: Abrupt transitions in habitat and biodiversity

Stream burial, the rerouting of streams into underground culverts, is common in industrialized and densely populated urban areas. While stream burial is common in urban environments, direct characterization of the within-culvert environment is rare and it is unclear if buried reaches reflect neighboring open reaches regarding habitat, biota, and water chemistry. Additionally, for a buried stream, the entrance and exit of the culvert are abrupt habitat transitions within the stream channel, and it is unknown if these transitions lead to similarly abrupt responses in biotic and abiotic characteristics or if responses are gradual. Quantifying the within-culvert environment and transitions upon entering/exiting the culvert has rarely been done but can help inform management practices regarding how these systems are impacted and establish a baseline for evaluating daylighting or stream restoration projects. To understand how culverts affect longitudinal biotic and abiotic characteristics of urban streams, we evaluated longitudinal patterns of physical habitat characteristics, stream water physiochemistry, periphyton biomass, and macroinvertebrate density and diversity in two urban streams that included long (>100 m) culvert reaches. Abrupt transitions in a suite of abiotic and biotic variables were observed at the entrances and exits of the culverts whereas some variables showed no response to the culvert presence. Periphyton biomass and macroinvertebrate density were reduced by 98% and 92%, respectively, by culverts in the two streams. Within the culverts, we observed greater water depths (average of 10 cm outside vs 26 cm within the culvert), finer benthic substrate, and diversity of macroinvertebrates was reduced by 50%. Nutrient concentrations, in contrast, showed no response to the presence of a culvert. Within 60–90 m downstream of the culvert exits, most of the measured parameters returned to levels similar to those observed upstream of the culvert, suggesting that the ecosystem impacts of urban culverts, though dramatic, may be spatially constrained.

Urban infrastructure influences dissolved organic matter quality and bacterial metabolism in an urban stream network.

1. Urban streams are degraded by a suite of factors, including burial beneath urban infrastructure, such as roads or parking lots, which eliminates light and reduces direct organic matter inputs to streams from riparian zones. These changes to stream metabolism and terrestrial carbon contribution will likely have consequences for organic matter metabolism by microbes and dissolved organic matter (DOM) use patterns in streams. Respiration by heterotrophic biofilms drives the nitrogen and phosphorus cycles, but we lack a clear understanding of how stream burial and seasonality affect microbial carbon use. 2. We studied seasonal changes (autumn, spring, and summer) in organic matter metabolism by microbial communities in open and buried reaches of three urban streams in Cincinnati, OH. We characterised DOM quality using fluorescence spectroscopy and extracellular enzyme profiles, and we measured the respiration response to carbon supplements in nutrient diffusing substrata (NDS). We hypothesised: (1) that algal production would lead to higher quality DOM in spring compared to other seasons and in open compared to buried reaches, (2) lower reliance of microbial respiration on recalcitrant carbon sources in spring and in open reaches, and (3) that microbial respiration would increase in response to added carbon in autumn and in buried reaches. 3. Several fluorescence metrics showed higher quality DOM in spring than autumn, but only the metric of recalcitrant humic compounds varied by reach, with more humic DOM in open compared to buried reaches. This likely reflected open reaches as an avenue for direct terrestrial inputs from the riparian zone. 4. Extracellular enzyme assays showed that microbes in buried reaches allocated more effort to degrade recalcitrant carbon sources, consistent with a lack of labile carbon compounds due to limited photosynthesis. Nitrogen acquisition enzymes were highest in autumn coincident with riparian leaf inputs to the streams. Buried and open reaches both responded more strongly to added carbon in autumn when terrestrial leaf inputs dominated compared to the spring when vernal algal blooms were pronounced. 5. Our data show that stream burial affects the quality of the DOM pool with consequences for how microbes use those carbon sources, and that heterotrophic respiration increased on carbon-supplemented NDS in buried and open stream reaches in both seasons. Different carbon quality and use patterns suggest that urban stream infrastructure affects spatiotemporal patterns of bacterial respiration, with likely consequences for nitrogen and/or phosphorus cycling given that carbon use drives other biogeochemical cycles. Management actions that increase light to buried streams could shift the balance between allochthonous and autochthonous DOM in urban streams with consequences for spatiotemporal patterns in bacterial metabolism.

Urban Stream Burial Increases Watershed-Scale Nitrate Export.

Nitrogen (N) uptake in streams is an important ecosystem service that reduces nutrient loading to downstream ecosystems. Here we synthesize studies that investigated the effects of urban stream burial on N-uptake in two metropolitan areas and use simulation modeling to scale our measurements to the broader watershed scale. We report that nitrate travels on average 18 times farther downstream in buried than in open streams before being removed from the water column, indicating that burial substantially reduces N uptake in streams. Simulation modeling suggests that as burial expands throughout a river network, N uptake rates increase in the remaining open reaches which somewhat offsets reduced N uptake in buried reaches. This is particularly true at low levels of stream burial. At higher levels of stream burial, however, open reaches become rare and cumulative N uptake across all open reaches in the watershed rapidly declines. As a result, watershed-scale N export increases slowly at low levels of stream burial, after which increases in export become more pronounced. Stream burial in the lower, more urbanized portions of the watershed had a greater effect on N export than an equivalent amount of stream burial in the upper watershed. We suggest that stream daylighting (i.e., uncovering buried streams) can increase watershed-scale N retention.

Regional scale selenium loading associated with surface coal mining, Elk Valley, British Columbia, Canada

Selenium (Se) concentrations in surface water downstream of surface mining operations have been reported at levels in excess of water quality guidelines for the protection of wildlife. Previous research in surface mining environments has focused on downstream water quality impacts, yet little is known about the fundamental controls on Se loading. This study investigated the relationship between mining practices, stream flows and Se concentrations using a SPAtially Referenced Regression On Watershed attributes (SPARROW) model. This work is part of a R&D program examining the influence of surface coal mining on hydrological and water quality responses in the Elk Valley, British Columbia, Canada, aimed at informing effective management responses. Results indicate that waste rock volume, a product of mining activity, accounted for roughly 80% of the Se load from the Elk Valley, while background sources accounted for roughly 13%. Wet years were characterized by more than twice the Se load of dry years. A number of variables regarding placement of waste rock within the catchments, length of buried streams, and the construction of rock drains did not significantly influence the Se load. The age of the waste rock, the proportion of waste rock surface reclaimed, and the ratio of waste rock pile side area to top area all varied inversely with the Se load from watersheds containing waste rock. These results suggest operational practices that are likely to reduce the release of Se to surface waters.

Effects of urban stream burial on nitrogen uptake and ecosystem metabolism: implications for watershed nitrogen and carbon fluxes

Urbanization has resulted in the extensive burial and channelization of headwater streams, yet little is known about the impacts of stream burial on ecosystem functions critical for reducing downstream nitrogen (N) and carbon (C) exports. In order to characterize the biogeochemical effects of stream burial on N and C, we measured NO3 − uptake (using 15N-NO3 − isotope tracer releases) and gross primary productivity (GPP) and ecosystem respiration (ER) (using whole stream metabolism measurements). Experiments were carried out during four seasons, in three paired buried and open stream reaches, within the Baltimore Ecosystem Study Long-term Ecological Research site. Stream burial increased NO3 − uptake lengths by a factor of 7.5 (p < 0.01) and decreased NO3 − uptake velocity and areal NO3 − uptake rate by factors of 8.2 (p < 0.05) and 9.6 (p < 0.001), respectively. Stream burial decreased GPP by a factor of 11.0 (p < 0.01) and decreased ER by a factor of 5.0 (p < 0.05). From fluorescence Excitation Emissions Matrices analysis, buried streams were found to have significantly altered C quality, showing less labile dissolved organic matter. Furthermore, buried streams had significantly lower transient storage (TS) and water temperatures. Differences in NO3 − uptake, GPP, and ER in buried streams, were primarily explained by decreased TS, light availability, and C quality, respectively. At the watershed scale, we estimate that stream burial decreases NO3 − uptake by 39 % and C production by 194 %. Overall, our results suggest that stream burial significantly impacts NO3 − uptake, stream metabolism, and the quality of organic C exported from watersheds. Given the large impacts of stream burial on stream ecosystem processes, daylighting or de-channelization of streams, through hydrologic floodplain reconnection, may have the potential to alter ecosystem functions in urban watersheds, when used appropriately.

One-Dimensional Fully Developed Turbulent Flow through Coarse Porous Medium

A fully developed turbulent regime is considered as a specific case of non-Darcy flow, and an analytical approach has been developed to determine normal depth, water surface profile, and seepage discharge of the flow through coarse porous medium in steady condition. The results of a laboratory rock drain with length, height, and width of 6.4, 0.8, and 0.8 m, respectively, and longitudinal slope of 0.04 were compared with the analytical solution developed in this study, and the results showed a good agreement between analytical and experimental data. To see the compatibility of the solution, a Darcy-based form of the solution (Pavlovsky’s method) and a flow analysis of buried streams (FABS) model are compared with the proposed solution and experimental data. Compared with Pavlovsky’s solution and FABS model, the results showed a satisfactory agreement with experimental records from water surface profiles through rock drain.

Hydraulic performance and stability of coarse rockfill deposits

Open-pit coal mining operations often generate enormous quantities of waste rock. This is dumped into nearby valleys and the coarsest fraction ends up at the bottom of the deposit; the final result is often referred to as a ‘rock drain’. These ‘flow-through’ rockfill drains can be 100 m high, thousands of metres long, and usually have a stream flowing through their base. When the stream that supplies the rock drain floods, the ability of the drain to convey water is exceeded by its supply, and a large but temporary pool develops at the upstream end of the dump. More importantly, the free surface within the rock drain becomes elevated, as does the point of exit at the downstream face. Because of historic instances of failures at the downstream face, the management of these buried streams and the hydraulic behaviour of the rock drains through which they flow are of interest. The behaviour of homogeneous embankments comprised of coarse rockfill has many similarities to the behaviour of long rockfill drains. Methods for assessing the hydraulic performance of either are presented herein. Definition of the complete water surface ‘envelope’ and the tendency toward unravelling of the downstream face receive primary focus. It is demonstrated that the hydraulic gradient directly beneath the seepage face and small variations in its direction play a far greater role than seepage-face overflow in promoting unravelling failure, and argues that all such deposits are, in effect, embankment dams that should fall under the applicable national dam safety regulations.

Application of gradually-varied flow algorithms to simulate buried streams

This paper reports the underlying algorithm, implementation, and development details of the Flow Analysis of Buried Streams (FABS) hydraulic model. This model simulates water surface profiles for 1-D non-Darcy flow through buried streams. Buried streams are formed in open-pit coal mines due to the disposal of large volumes of coarse rockfill. In such buried streams the formerly open channel passes through very coarse porous media but the behavior of this flow does not follow Darcy's law. Rather, it behaves in a manner similar to that of ordinary open channel flow. The longitudinal variation in the depth of water along the stream is not, however, governed by the roughness of the stream-bed, but by the characteristics of the coarse porous media that now fills the channel. Such flow is governed by non-Darcy flow operating under the Dupuit assumptions. The performance of the model in simulating steady non-Darcy flow profiles was evaluated under laboratory experimental conditions and found to be satisfactory. The model uses either Wilkins' or Stephenson's equation to compute head losses. It was found that these equations performed equally well in simulating experimental water surface profiles. The performance of the model was also evaluated under three different friction-slope averaging methods, namely, the arithmetic, geometric, and harmonic average. Based on the results obtained in this study, it is suggested that any of these frictions-slope averaging techniques result in satisfactory flow profiles, provided that reach lengths are not excessive. Although there are certain limitations and definite possibilities for further improvement, it is believed that the FABS model represents a significant step forward in providing more explicit assistance in the non- Darcy water surface profile simulation process.

Uncertainty in Water Surface Profile of Buried Stream Flowing under Coarse Material

Non-Darcy flow occurs when a hydraulic gradient is set up across a matrix of coarse porous media, resulting in turbulence in the void spaces. Buried streams that are formed at open-pit coal mines in mountainous areas (due to the disposal of large quantities of waste rock in valley terrain) are good examples of this phenomenon. An overview of the sources of uncertainty associated with non-Darcy water surface profile computations is presented. Numerical and experimental examples are used to illustrate how the mathematical developments presented in this paper can be used to quantify some of the inherent uncertainties. A model buried stream built as part of this study was used to test these mathematical developments. The performance of an equation for optimizing cross-section spacing is described. Uncertainty equations developed using first-order uncertainty analysis are applied to a rectangular stream. A procedure for quantifying the probable error in the computed depth of flow is illustrated herein by applying a simplified form of the total uncertainty equation to a model buried stream. Based on these results, guidance is provided for the uncertainty analysis of water surface profiles for field-scale buried streams.

Measurement of the Density of Watercourses with Mesh Method

Method for measurement of the density of watercourses is developed to know whether people have watercourses in their neighborhood or not.Meshes of 500m*500m unit size are set on Iriegawa-Takinokawa basin in Yokohama city, and measurement of the length of watercourses per unit mesh is performed.Meshes are divided into four grades; A (0m/ha), B (0-10), C (10-20), D (more than 20), and classified as shown in Fig. 2.Most of meshes in Fig.2 are ranked A or B (under 0-10m/ha), and people in these meshes have scarce watercourses in their neighborhood.Renovation of the buried streams and ponds is necessary in these areas.