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science and policy research: urban streams 2nd Symposium on Urbanization and Stream Ecology Note: Links are to powerpoint presentations in PDF format. Friday, May 23 Presentation of conceptual model (SJ Wenger) I. Stressors A. Is Impervious Cover Still Important? A Review of Recent Research The Impervious Cover Model (ICM) has attracted considerable attention in recent years, with nearly 250 research studies testing its basic hypothesis that the behavior of urban stream indicators can be predicted on the basis of the percent impervious cover (IC) in their contributing subwatershed. The majority of research published since 2003 has confirmed the basic premise of the ICM, but has also revealed important caveats and limitations to its application, and tested the possible effect of watershed treatment, such as stormwater treatment practices and riparian forest cover. The ICM continues to be a useful planning and forecasting tool, and provides a useful foundation for designing regional subwatershed management classification systems. The paper concludes with recommendations for improving the consistency of future stream research studies, and testing the watershed treatment hypothesis. B. Hydrologic and Geomorphic Change in Urban Streams: What We Know, What We Don't Know, and What We Need To Know The United Nations predicts that the world's population from 2005 to 2050 will expand from 6.5 billion to 9.1 billion inhabitants. With such extreme population growth, continued urbanization of the world is inevitable, severely impacting our aquatic ecosystems by increasing degradation of our rivers and streams. In the last half a century, much research has been conducted to help us understand the impacts humans have on stream channels. Changes in watershed hydrology often lead to channel enlargement, which in turn impacts channel sediment dynamics. However, there is much site-to-site variability and in-stream impacts have been found to vary depending on age and type of upstream development. In addition, many questions remain concerning the time period of channel adjustment due to urbanization, and whether or not they eventually reach a different, but 'stable' geometry. The evolution of streams undergoing urbanization is difficult to observe, and rarely documented. This review attempts to summarize the current state of knowledge regarding urban hydrology and resulting physical impacts on streams. In particular, the focus will be on where there is the most uncertainty and what we really need to know in order to understand, protect, and restore urban streams. C. Urban Stream Water Quality- a Product of "Urban Karst"? Urban streams have long been known to have poor water quality due to stormwater runoff and sewer/illicit connections. However, understanding how these impacts modulate aquatic ecosystems requires a highly interdisciplinary, multi dimensional approach. Just as aquatic ecologists have come to realize the importance of hyporheic and watershed influences on stream ecological structure and function, we are realizing that urban systems are not simply runoff conveyance systems, but affect streams at an additional level of complexity. Of great importance is the degree of connectivity between civil infrastructure and urban streams, which goes far beyond the routing of stormflow and includes flow augmentation by potable water networks as well as upland and riparian influences from sanitary sewers. Almost every hectare of the urban landscape is underlain by this dense network of pipes which create a kind of "engineers karst" which not only affects hydrologic processes, but creates a previously under-appreciated "gutter subsidy" for organic matter and other material to urban streams. Moreover this extension of the stream network extends to almost every drainage feature in the landscape, essentially making every gutter and rooftop a zero order stream. We discuss various aspects of these complexities with respect to how they create a new "urban stream continuum" and determine water quality in urban streams and constrain their aquatic communities. D. The Tao of Stormwater: Water Quality and Hydrologic Changes are Inseparable, Complementary Impacts of Stormwater Runoff There is ample evidence in the literature that stormwater alters stream ecosystems through diverse water quality and hydrologic impacts. The question, 'is stormwater more a problem of hydrology than of water quality?', is often posed with an underlying assumption that stormwater's most important hydrologic impact is the increased size of large storm events, consistent with management responses that focus on reduction of pollutant loadings and peak discharges. Less commonly considered, the increased frequency of small runoff events from conventional stormwater drainage, and the reduction of dry-weather flow produce a cascade of ecological impacts beginning with a decline in many aspects of water quality between large storm events. Addressing water quality between large events requires retention and treatment in the catchment of stormwater from small events, which in turn demands a new focus on reduction of water volume running off urban impervious surfaces. Thus water quality and hydrologic effects of stormwater are not only tightly bound as a problem, but also in its solution. E. Stressors: recent research 1. Pick Your Poison: The Relative Effects of Climate Change and Urbanization on Stream Hydrology Climate models predict an array of changes to streams including hydrologic change. Climate impacts, however, occur over a template of land use changes, including urbanization. An important question is the extent to which climate impacts will overwhelm, interact, or counteract urbanization impacts. Climate predictions for the Mid-Atlantic US vary, but a common prediction is for the same amount of precipitation to occur in fewer, larger storms. We used historic precipitation data to identify years with normal (± 1 sd) precipitation which occurred during fewer than normal (< 1 sd) storms. We then used historic hydrologic data to compare normal climatic years with "future climate" years in terms of hydrologic response. To contrast the climate effects with land use, we compared predominantly forested catchments with predominantly urban catchments. Urbanization had an overwhelming impact on high-flow indicators relative to future climate. In contrast, future climate had a stronger effect on low-flow indicators, frequently overwhelming any impact from land use. We infer that urbanization will continue to result in high-flow mediated stresses in Mid-Atlantic streams and this affect will overwhelm any climate impacts, while climate change will result in strong effects on low flow hydrology which pose a serious threat to stream ecosystems. 2. Suburbanization and Water Quality in SE New Hampshire - the Lamprey River Hydrologic Observatory The Lamprey River Hydrologic Observatory (LRHO) was established in 2000 to address to address the effects of land use and increasing population density on water quality. A major focus is to understand the effects of suburbanization on hydrology and biogeochemical cycles throughout the basin. Sub-basins have been instrumented, and we have established long-term sampling sites in headwaters and main stem throughout the basin. Results to date show strong variation in surface water and groundwater nitrate with human population density, chloride levels in surface and groundwater that are close to exceeding EPA drinking water or aquatic health criteria, and increasing nitrate concentrations in the main stem Lamprey over the past seven years. Despite the obvious human imprint on the landscape, overall N flux from the basin is moderate, with apparent N retention/loss in riparian zones, wetlands, or due to in-stream processes. 3. High Resolution Mapping of Spatial and Seasonal Water Quality Variability in Urban Rivers: An example from the Hillsborough River, Tampa Florida Urban rivers, estuaries, reservoirs, and lakes are multi-use systems that supply water for agricultural, industrial, and human use. Existing methods of collection (grab sampling or point monitoring with field meters) are limited to viewing water quality as snapshots in space or time, leaving the desired comprehensive, large scale overview missing. A ccelerating the integration of off-the-shelf technology - in situ sensors (CTDs, YSI sondes©), geospatial display techniques (GoogleEarth©, ArcView/GIS), and autonomous sampling platforms (tow bodies, profilers, ROVs) - can provide improvements in assessment and mitigation activities at the site to reach scales through high resolution data collection and visualization. We provide a demonstration of this integration in the Hillsborough River, a dammed and navigable coastal river flowing through the second largest city in Florida. Results include 2-D maps of temperature, conductivity, salinity, turbidity, chlorophyll florescence and chromophoric dissolved organic matter (CDOM). These kriged maps show small scale influences of significant features missed by snapshot or grab sampling techniques: from tributary confluences, submarine groundwater plumes, floodplain/riparian connections and other patchily distributed hydrogeomorphological features. 4. Hydrology and Nitrogen Biogeochemistry in the Hyporheic Zone of a Geomorphically Degraded Urban Stream Few studies have investigated the relationship between hydrology and nitrogen biogeochemistry in hyporheic zones of degraded urban streams despite significant national efforts to restore such streams. We examined relationships between hydrology and biogeochemistry in Minebank Run, a geomorphically degraded urban stream near Baltimore, Maryland, that exhibited "urban stream syndrome" characteristics including steep bank incision and flashy hydrology stemming from altered runoff from surrounding impervious surfaces. Hyporheic NO 3 ¯ was inversely related to DOC ( R 2 = 0.64, P = 0.01) but not to any other chemical variable. The redox environment of the subsurface was closely linked to ground water elevation ( R 2 = 0.96, P = 0.004). Hyporeheic NO 3 ¯ was positively related to mean water table elevation ( R 2 = 0.69, P = 0.01), DOC was inversely related to water table elevation ( R 2 = 0.5, P = 0.05), whereas Cl, a conservative natural tracer in this system, was not related to ground water level. Thus, NO 3 ¯ concentrations in the hyporheic zone of this degraded stream were strongly influenced by both DOC availability and ground water topography. Stream restoration efforts that increase DOC availability and which address flashy hydrology (e.g. reduce stream flow velocities and/or increase ground water residence) are likely to improve the nutrient uptake capacity of urban streams. 5. Dissolved Organic Matter and Emerging Contaminants in Urban Stream Ecosystems We investigated the effects of urbanization on the sources, bioavailability and forms of natural and anthropogenic organic matter found in streams located in Maryland, U.S.A. We found that the abundance, biaoavailability, and enzymatic breakdown of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved organic phosphorus (DOP) increased in streams with increasing watershed urbanization suggesting that organic nutrients may represent a growing form of nutrient loading to coastal waters associated with land use change. Organic carbon, nitrogen, and phosphorus in urban streams were elevated several-fold compared to forest and agricultural streams. Enzymatic activities of stream microbes in organic matter decomposition were also significantly altered across watershed land use. Chemical characterization suggested that organic matter in urban streams originated from a variety of sources including terrestrial, sewage, and in-stream transformation. In addition, a characterization of emerging organic contaminants ( polyaromatic cyclic hydrocarbons, organochlorine pesticides, and polybrominated diphenyl ether flame retardents), showed that organic contaminants and dissolved organic matter increase with watershed urbanization and fluctuate substantially with changing hydrologic conditions. Elucidating the emerging influence of urbanization on sources, transport, and in-stream transformation of organic nutrients and contaminants will be critical in unraveling the changing role of organic matter in urban stream ecosystems. II. Responses A. The Urban Stream Food Web: Synthesis of Recent Investigations and a Look Ahead Research has repeatedly demonstrated declines in assemblage richness, diversity, and biotic integrity with increasing urbanization. Benthic macroinvertebrates are among the most widely studied organisms and have exhibited consistent responses to urbanization. Some recent macroinvertebrate studies have focused on spatial (longitudinal and habitat-specific) and temporal (seasonal) differences, and using species traits to identify mechanistic response. For fish, assemblage responses to urbanization are often linked to geomorphic and temperature shifts; where urbanization only affects water quality, fish responses are inconsistent. Macroinvertebrate and fish assemblages exhibit a range in threshold responses (declines have been shown from 4-13% imperviousness), and studies also report linear and curvilinear responses, highlighting the extreme variability in response patterns. Although less studied, diatom indices show consistent, negative responses to wastewater effluent and nonpoint urbanization sources. Many recent studies have reported increases in algal biomass with urbanization, and this response is often attributed to increased nutrients, rather than increased light. The limited studies on stream amphibians and reptiles and riparian birds suggest they may also be good indicators of habitat and stream quality. This synthesis will discuss uncertainty in ecosystem structure responses, and highlight important areas of future research to advance our understanding of urban stream ecosystems. B. Ecosystem Function in Urban Streams: Consistent and Variable Responses Ecosystem function describes processes that integrate transformations of materials or energy flow of multiple biotic and abiotic elements at the scale of whole ecosystems. In streams, ecologists have focused on ecosystem metabolism and nutrient transport, transformation and retention. In the face of urbanization, multiple stressors affect stream ecosystem function via changes in inputs, ecosystem structure, and disturbance regime. For each of these drivers of change in function, we consider which responses are consistent across streams within different biomes, and which are more context-specific. We rely for this analysis on literature reports primarily in the past five years. C. Spatial variation in ecosystem responses to urbanization 1. Overview of the USGS National Water Quality Assessment Program Study on Effects of Urbanization on Stream Ecosystems As land areas urbanize, stream ecosystems can be substantially altered. Watershed urbanization may cause changes in stream hydrology, water quality, physical habitat, and water temperature that, in turn, are known to have profound effects on aquatic communities of algae, invertebrate and fish. The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program study on the Effects of Urbanization on Stream Ecosystems (EUSE) examines the magnitude and pattern of response in stream biological communities, hydrology, habitat, and water chemistry as watersheds are urbanized in nine U.S. metropolitan areas. EUSE has focused on three questions. Do physical chemical, and biological factors associated with stream ecosystems respond to urbanization? What is the form of that response? How does that response vary across the United States? 2. Responses of Benthic Macroinvertebrates to Environmental Changes Associated with Urbanization in Nine Metropolitan Areas of the Conterminous United States The effects of urbanization on benthic macroinvertebrates were investigated in nine metropolitan areas as a part of the U.S. Geological Survey National Water Quality Assessment Program. Invertebrates showed strong, linear responses to urbanization when forest or shrublands were developed. Responses were difficult to discern in areas where urbanization was occurring on agricultural lands because invertebrate assemblages were already severely degraded. There was no evidence that assemblages showed any initial resistance to urbanization. Ordination scores, EPT taxa richness, and the average tolerance of organisms at a site were the best indicators of changes in assemblage condition. Richness metrics were better indicators than abundance metrics and qualitative samples were as good as quantitative samples. A common set of landscape variables (population density, housing density, developed land cover, impervious surface, and roads) were strongly correlated with urbanization and invertebrate responses in all non-agricultural areas. The instream environmental variables (hydrology, water chemistry, habitat, and temperature) that were strongly correlated with urbanization and invertebrate responses were influenced by environmental setting (e.g., dominant ecoregion) and varied widely among metropolitan areas. Consequently, landscape variables were better predictors of invertebrate responses than were instream environmental variables. 3. Changes in River-Channel Characteristics Due to Urbanization in Nine Metropolitan Areas of the United States From 2000-2004, the U.S. Geological Survey conducted a study of urbanization effects on stream ecosystems in nine metropolitan areas across the U.S. as part of the National Water-Quality Assessment Program. A rural to urban land-cover gradient approach was used. Geomorphic characteristics of river channels were compared to indicators of urbanization, watershed land cover, physiography, climate characteristics, and hydrologic-condition metrics. Information on channel engineering (channelization, bank stabilization, and grade control) and presence of bars and bedrock also was compiled. Channel size increased (through incision or widening) as total impervious surface and frequency of high flow events increased in three metropolitan areas. The lack of increased channel size with urbanization in other areas was likely because of preexisting drainage modifications, unstable channels, and presence of low head dams. The relation of channel shape, amount of bars, and streambed substrate with urbanization was complex, likely because the type, amount, and source of sediment may vary with phases of urbanization. Subtle variations in reach slope affected streambed substrate and habitat complexity (percent of riffles and runs) more so than urbanization. Bank erosion increased with increasing urbanization in some metropolitan areas, but responses were potentially affected by presence and age of local channel engineering (bank stabilization and grade control) and the qualitative nature of the measurements. 4. The Response of Algal Assemblages to Urbanization and Environmental Factors in Nine Metropolitan Areas of the United States From 2000 to 2004, the National Water-Quality Assessment (NAWQA) Program of the USGS conducted studies to determine the effects of urbanization on stream ecosystems in nine major metropolitan areas across the U.S. At about 30 sites in each study area, various biological, chemical, and physical components of stream ecosystems were assessed. Benthic algae were one of the biological components surveyed, and a primary objective of the study was to determine if changes in their assemblages (i.e., algal response) could be directly related to urbanization as characterized by an urban intensity index (UII), or if the algal response was more clearly related to environmental factors at either the watershed (distal) or reach (proximal) scale. PCA ordination site scores were used to characterize environmental factors at the two scales: (1) watershed-scale factors were derived from landcover, infrastructure, and census data; and (2) reach-scale factors were derived from habitat, streamflow, water-chemistry data. Algal responses were characterized as changes in the values of: (1) selected metrics that represented algal structure and function attributes; and (2) site scores derived from n onmetric m ulti d imensional s caling (NMDS) ordinations of the algal assemblages. The results indicated that across the U.S., diatom assemblages differed more strongly by geographic region than by any response driver within a study area. Of the response drivers, ambient water quality, rather than urbanization, was most strongly correlated to the algal response in six study areas. Landuse and hydrology were the most important response drivers in two other study areas, whereas one study area had experienced a severe drought over the sampling season that was believed to have suppressed any clear relation of the algae to urbanization or to water quality. 5. Relation of Urbanization to Stream Fish Assemblages and Species Traits in Nine Metropolitan Areas of the United States We examined associations of fish assemblages and fish traits with basin-scale urbanization and reach-scale environmental variables, including flow, habitat, and water quality, in 9 major metropolitan areas across the United States. The strongest relations between fish assemblages and urbanization effects on streams were found in the metropolitan areas of Atlanta, Georgia; Birmingham, Alabama; Boston, Massachusetts; and Portland, Oregon. In these areas, environmental variables were highly correlated (r s = 0.70) with both fish assemblages and the extent of urbanization. Overall, fish assemblages correlated more strongly with urbanization than fish traits. Fish assemblages and traits were poorly correlated with urbanization in Denver, Colorado; Dallas-Fort Worth, Texas, Milwaukee-Green Bay, Wisconsin, and Raleigh, North Carolina. Differences among areas in responses of fish assemblages to urbanization may be related to previous landscape disturbances, such as agriculture. Given the complexities of urban landscapes, our results suggest that caution is warranted when generalizing about biological responses to urbanization based on results from different metropolitan areas. Management in metropolitan areas with streams in good condition will likely focus on maintaining existing ecological conditions. Well planned urbanization of previously disturbed landscapes may offer resource managers the opportunity to improve previously degraded streams. D. Ecosystem responses: recent research1. Hydraulic Metrics Using HEC-RAS: A Tool for Determining Mechanisms and Management-Oriented Variables Aquatic biological conditions may be influenced by both hydrologic (i.e. magnitude, duration, frequency, rate of change) or hydraulic (i.e. depth, Froude number, shear stress) conditions. In a 2004 NAWQA Effects of Urbanization on Stream Ecosystems study we utilized a 1-dimensional hydraulic model (HEC-RAS) with habitat and continuous stream stage data to calculate hydraulic characteristics at 30 small (11-119 km 2 ) Western Lake Michigan watersheds. Utilizing correlation and multivariate regression tree modeling we evaluated the association between aquatic communities (fish, invertebrates, and algae) and hydraulic characteristics based upon hourly and daily time series resulting from 1-dimensional hydraulic modeling. Conceptually, the hydraulic characteristics provide insight about the link between watershed change, instream physical conditions, and stream biology. Furthermore, the hydraulic time series variables may provide deterministic or process insight not obtainable from the more general flow regime hydrologic metrics. Values of hydraulic variables may also reflect modifications at the immediate reach scale thus providing a potential link between channel modification and biology. Hydraulic characterizations of reach conditions should be considered as one quantification approach in a much larger tool box. 2. Suburban impacts on nitrogen fluxes at the scale of river networks Suburbanization is a widely distributed phenomenon that leads to relatively diffuse local impacts compared to high density urbanization. Impacts may however accumulate as these distributed suburban areas become linked through the river network draining a region. Alternatively, impacts may become attenuated in transit through the river network by dilution or biological activity. River network models are needed to explore these interactions. In this study, a river network nitrogen (N) removal model was used to explore the ability of river systems to attenuate N fluxes associated with increased suburbanization. The model was applied to the 400km2 Ipswich R. watershed (a 5 th order river network) in northeastern MA, which consists of 30% suburban land use resulting from the proximity to Boston. The model accounts for the distribution of elevated N inputs, hydrologic conditions, and aquatic biological processes that can remove N from water (i.e. denitrification). The model predicted that between 15 and 33% of annual DIN inputs were denitrified annually by channel processes. The model was used to explore how the distribution of land use and future increases in N loading might influence river network capacity to attenuate nutrient fluxes. Because denitrification process saturates, the proportion of inputs removed by the river system is expected to decline at increasing rates with continued suburbanization. 3. Effects of urbanisation on the diversity of bacteria and ciliates in stream biofilms Bacterial and ciliate diversity were compared in biofilms collected from rock surfaces in forested, urban fringe and fully urban stream sites over several seasons. Population diversity was assessed by ARISA (automated intergenic spacer region analysis) and T-RFLP (terminal restriction fragment length polymorphism) molecular community profiling techniques for bacteria and ciliates respectively. Community profiles were analysed by multidimensional scaling to assess similarity. Distinct differences in population structure were identified between each of the 3 sites for most seasons for each group of organisms. The urbanised site showed the greatest community separation distance from the other sites but, interestingly, showed a similar level of bacterial and ciliate diversity at genus level. Parallel studies using 16 and 18sRDNA sequencing showed that the dominant populations of organisms at were largely different, at species or genus level, between the sites. Initial experiments to assess the drivers of the population differences between the urban and forested streams suggest that heavy metals from storm water are an important selective factor of both ciliate and bacterial diversity in urban stream biofilm communities. This research is ongoing and will further assess the functional role of bacterial subpopulations in the stream food web. 4. Effects of Urban Development on Headwater Stream Condition: An Assessment Using Relationships among Land Cover, In-stream Physicochemical Features, and Benthic Macroinvertebrate Community Attributes Urbanization is associated with declining stream condition, reflected by several indicators of reduced water and habitat quality. Stream degradation is exacerbated by lack of knowledge about consequences of urban development. Impacts of development on headwater streams can be severe but also relatively easy to detect. We are assessing urbanization effects on condition of headwater streams in central Iowa by quantifying stream physicochemical and biological (macroinvertebrate community) features at agricultural and urban locations, and relating these features to land cover characteristics. Early results suggest that streamwater concentrations of total phosphorus increased with urban development, whereas highest nitrate concentrations and turbidity were found at agriculturally-impacted sites. Ecologically sensitive macroinvertebrates appeared to respond negatively to urban development. In particular, EPT (Ephemeroptera, Plecoptera, Trichoptera) family richness, and percentage of total macroinvertebrate abundance composed of EPT, declined with increasing percentage of urban land cover in the surrounding landscape. At both agricultural and urban sites, EPT family richness was positively related to abundance of coarse substrate (e.g., cobble, boulders) on the streambed. Several management practices that can maintain and increase availability of coarse substrate (e.g., erosion control through planting of streamside vegetation buffers) are being installed at our study sites to improve water and habitat quality. 5. The Adult Assemblage of Aquatic Insects Indicates Recruitment Limitation in Urban Headwater Streams The ontogenetic shift between aquatic and terrestrial habitats is a key feature of aquatic insect life cycles, yet its role in population dynamics has received little attention, particularly for inhabitants of urbanized streams. Poor in-stream habitat quality lowers larval survival for intolerant species in urban streams, but impacts to adults and habitat fragmentation may constrain recruitment of the next generation of larvae and intensify the impact of watershed urbanization. Our work examining insect assemblages and community similarity in urban and rural headwater streams suggested that impacts to larvae from in-stream habitat degradation is not the sole determinant of stream insect community composition. Greater similarity between the main-stem and headwater insect communities suggested that the main-stem may be a source of recruits for the headwater. Further preliminary work examining adult Trichoptera activity indicated that a lack of adult immigrants may contribute to low diversity. Overall, diversity of the adult assemblage was lower for urban headwaters. Some taxa however, may not be experiencing constrained recruitment from a lack of adults. Several larval taxa absent from the urban headwater were found to be present as adults. III. Management A. The latest generation of policies for managing urban stressors 1. Is Impervious Cover Still Important? Watershed Management Implications The ICM has engendered considerable debate among planners, engineers and regulators. Many communities struggle on how to influence the location and intensity of subwatershed impervious cover (IC) and/or apply techniques to mitigate its impact. This paper evaluates the broader implications of the ICM for local watershed management efforts and reviews the full range of watershed planning, engineering, economic and regulatory tools that can manage the intensity, location and impact of IC on receiving waters. The strengths and weaknesses of each of these tools are assessed. It is argued that only the combined application of multiple planning, engineering, economic and regulatory tools can provide maximum protection or restoration for a given subwatershed when subwatershed IC is forecast to increase to future growth and development. 2. Towards New Objectives for Stormwater Management Hydraulic connection is likely the most important attribute of impervious surfaces determining their impact on receiving streams. The steep decline in ecological condition of streams with very little percentage impervious cover that is directly connected to streams suggests that protection of stream ecosystems requires a base objective of zero connected impervious cover. This shifts the focus of stormwater management objectives to the adequate disconnection of all impervious surfaces. We propose a new index, retention capacity (RC), which can be applied as an objective at a range of scales, from land parcel to region. RC quantifies the degree of hydraulic connection of impervious surfaces, and is scaled to the frequency (and, implicitly, the magnitude) of storm event required to form a direct hydraulic connection between an impervious surface and the nearest drain or stream. RC emphasizes the importance of mimicking natural runoff behaviour, at least for small, frequent storms, and provides a conceptual link between catchment- and regional-scale models predicting response of in-stream ecological indicators to connected imperviousness, and the small-scale design requirements for treatment systems. Its application requires a focus on near-source retention of small rain events, to reduce the volume and frequency of stormwater delivery to waterways. 3. Targeting Landscape Features for Urban Stream Policy Urban stormwater policy commonly targets stormwater discharges into receiving water bodies either through point or nonpoint source standards and controls. These types of regulatory approaches indirectly may lead to changes in the landscape as the regulated community meets water quality or quantity standards through modified development designs or engineered stormwater controls. A complementary approach is to design policies that directly target landscape characteristics to manage stressors to urban stream systems. We briefly discuss three forms of this type of regulation: riparian buffer management, erosion and sediment control, and the use of government incentives to encourage green infrastructure protection. From these examples, we identify guiding principles that can help make landscape policies more effective for protecting urban stream systems.
Combining stormwater standards with these landscape-scale approaches helps policy-makers comprehensively manage urban landscapes to protect aquatic ecosystems. B. Do We Understand What's Broken? Current and Future Challenges to Restoring Urban Streams Watershed urbanization degrades draining streams in a variety of ways. The predictable effects of increased impervious cover on stream hydrographs and the resulting alteration in stream geomorphology are well known. Similarly, the loss of sensitive macroinvertebrates and increase in nutrient concentrations associated with watershed development are also well described. Yet the effects of urbanization on stream ecosystem function are both less studied and less clear. Urban stream restoration efforts typically set goals of improving water quality and providing improved habitat, yet there is little evidence to date to suggest these goals are met. In this talk I will discuss the current limitations of the field of dreams approach to urban stream restoration, and the research challenges we must overcome in order to effectively improve stream water quality and minimize urban impacts on downstream ecosystems. C. Re-inventing Urban Streams As humans have adapted natural systems to their needs, the variability so characteristic of stream ecosystems has been greatly reduced. This is particularly true in urban environments where landscapes are often designed to conform to rigid specifications. For example, urban streams are not free to move across the landscape unimpeded by infrastructure even though in their native state, they constantly 'adjust' to changes such as altered sediment and water fluxes. Such adjustments allow rivers to absorb disturbances and act to buffer their biota and the river corridor from the impacts of acute stress, anthropogenic activities, and, even, environmental "surprises". If we view urbanization as a stressor that progressively constrains the ecological, geomorphic, and hydrologic character of a stream, what is reasonable to "ask" of our rivers and streams? I argue that contrary to current views and practices, we can not expect to benefit from all or most of the ecosystem services we typically associate with running-water systems. Instead, we must prioritize what we want/need from urban streams and develop novel strategies for achieving those goals. This will mean a fundamental re-conceptualization of urban stream design and restoration - we must re-invent them to meet societal needs and to be more self-sustaining than they are at present. Instead of using templates or reference reach approaches, I argue for design, conservation, and restoration approaches that promote the functionality and resilience or urban streams as socio-ecological systems. D. Urban stream management: recent research1. Impacts of Land Disturbance on Aquatic Ecosystem Health: Quantifying the Cascade of Events for Use in Ecological Risk Assessment Research has shown a correlation between land use and decline in biotic integrity in aquatic systems. Land use changes in a watershed frequently result in physical stressors, such as changes in flow regime and habitat that affect the ecological integrity of the stream. The objective of this study was to quantify the mechanisms of aquatic ecosystem degradation in a stream as the watershed undergoes urbanization. By quantifying the development level and the changes in the physical parameters of the stream, the effects of land use change can be evaluated using a traditional ecological risk assessment framework. Three first-order streams near Greenville, SC at various stages of land development were examined. A disturbance index to quantify the monthly changes in the planned land use change was developed. Changes in habitat, stream morphology, flow, total suspended solids (TSS), and benthic invertebrate indices were related to a normalized disturbance index for the watershed land area. Quantitative negative relationships between the development level in the watersheds stream habitat, median bed sediment size, and the Benthic Index of Biotic Integrity (B-IBI) were established. Runoff volumes, TSS concentrations, and the North Carolina Index of Biotic Integrity (NCBI) had positive relationships with development level. Through stepwise regression modeling, the most influential physical stressors on ecological integrity of streams are identified for development of regulatory criteria and incorporation into decisions regarding land use. 2. Addressing Urbanization in CADDIS CADDIS, the U.S. EPA's Causal Analysis/Diagnosis Decision Information System, is an online application designed to help users find, access, organize, use and share information relevant to causal assessments in streams and rivers. Much of the information presented on CADDIS focuses on specific stressors; for example, candidate cause modules in CADDIS contain key summary information for eight common stressors (e.g., sediment, nutrients, temperature). However, many users are faced with suites of multiple, co-occurring stressors that result from specific sources, suggesting that development of source-based material may be useful. In many regions, urbanization is a significant contributor to stream impairment. We propose to test a source-based approach in CADDIS by developing a prototype urbanization module for the website. A key component of this module will be a conceptual diagram illustrating linkages between sources, stressors, and biological effects commonly associated with urbanization, which will serve as a structural framework for organizing and displaying information and research on urban streams. We hope to make this diagram the framework for a pilot collaborative platform, whereby individual users collectively populate the diagram with relevant information, including stressor-response relationships, methods and measurements, and supporting references. 3. Retrospective Assessments of Streams Draining Ideal Developments: Unplanned Experiments to Explore the Upper Boundaries of Stormwater Mitigation In the early 1990s, several mixed-use Urban Planned Developments were proposed in King County to create small cities on forested glacial ridges drained by sensitive headwater streams. King County required the most stringent stormwater controls of the time: maximum infiltration, flow duration control to prevent stream erosion, large riparian buffers, and significant forest and open space preservation. Streamflows were modeled and mitigations were designed with continuous hydrologic models (HSPF) calibrated with on-site flow and climate data. Development of these projects took more than a decade, and during that time most monitoring was suspended. The developments are now nearly completed, and in October 2007, authors visited streams draining these developments to consider approaches to the fundamental question, "did the mitigations protect the streams as intended?" Visual inspection suggested the hydrologic mitigations have been largely successful as the streams showed no signs of instability typically accompanying such developments, despite experiencing an exceptional winter storm in November 2006. These UPDs present an excellent opportunity to assess whether best-available stormwater management in the early 1990's was sufficient to protect downstream water quality and biological integrity. The pre-development monitoring was not rigorously designed to answer questions about stream responses to development, and a BACI design is not possible for this assessment. Strengths and limitations of several possible retrospective study designs will be discussed. 4. Local Participation in Storm Water Management and Urban Stream Restoration Efforts in Iowa Local residents, city officials, and developers in urban areas differ with respect to their levels of knowledge and concern about urban impacts on stream ecosystems. In Iowa, even though all of these stakeholders express that urban streams are very important to them, they often have a limited understanding of best management practices (BMPs) designed to protect urban streams from the impacts of storm water generated in their municipalities or even on their own properties. We are conducting a study that integrates implementation and evaluation of urban stream BMPs with outreach to local partners, focused primarily on one urban headwater stream. The project includes installation of infiltration gardens on private property, a vegetated riparian buffer on public property, and a surface sand filter on a university campus. Impacts of these best management practices on stream channel condition, water quantity, and water quality are being studied over time, and compared to those of an unmanaged stream. Outreach efforts with local residents indicate that ongoing and sustained interaction using a variety of mechanisms is important, and that higher levels of engagement occur when activities are conducted on-site and include hands-on components (participatory design, project tours, and on-the-ground maintenance activities). 5. Restoration and Remediation of Urban Streams: Are We Missing the Point? Management agencies have made considerable investments into restoring and re-mediating urban stream networks. Most notably, these include riparian replantings and the use of stormwater control wetlands to moderate hydrological and water quality effects. Using streams in the metropolitan area of Melbourne we investigated the potential for riparian plantings and stormwater wetlands to restore invertebrate communities and remediate water quality. We found some evidence for a positive effect of riparian plantings on invertebrate diversity, particularly in a very heavily degraded site. There was no evidence of a positive effect of stormwater wetlands on either invertebrates or water quality. We conclude that while there may be some minor improvements in streams from these measures, the dominant influence of water quality and hydrology requires much more far-reaching management than is currently undertaken. Saturday, May 24 I. Presentation of research questions (SJ Wenger) II. Management panel: What are top priority state and local research needs? A. Dave Courtemanch, State of Maine Bioassessment Group (biologist) B. Ron Bowen, Director of Public Works, Anne Arundel County, Maryland (engineer) C. Bill Stack, Chief, Water Quality Management Section, Baltimore City Department of Public Works, Maryland (engineer) (Note: presentation given without powerpoint) D. Joseph MacDonald, Program Development Senior Associate, American Planning Association (planner) |
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