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research: urban streams Responses are listed below, unedited except to correct obvious typographic errors. The list of questions that you sent around was great. I note that there wasn't anything about nutrients though. There is great interest in many parts of the world in the ability of urban streams to retain nutrients. And to restore this ability. Is there a major driving factor of ecological degradation in urban streams? If so, what is it and how can we manage for it? How to we tease apart the cumulative effects of multiple stressors in urban streams? Is it "worth it" to attempt restoration in urban catchments? If so, what types are most effective? Is it possible do catchment scale research and manipulations to test some of these hypotheses (i.e. implementing structures/flow management in new developments)? Biogeochemical and microbial effects. Relationship between riparian vegetation and those. Monitoring the efficacy of stormwater control measures.How to conduct effective biological restoration under constrained circumstances. Teasing out water quantity (hydrograph modifications) vs quality in terms of what are the major factors behind degradation of the biotic community. Impact of storm water discharges as a stressor and impact of urban roadways on chemistry and flows, not currently regulated. Restoration results in urban streams, especially 319a projects. Following up on the results of hypothesis generating observational studies with hypothesis testing laboratory/controlled studies Since I'm an engineer/hydrologist/geomorphologist hybrid, I'll go with the 1st two bullets in your proposed framework as being the most important to me. In particular, 1) Importance of contaminants versus physical impacts (hydrologic and morphologic/habitat). Which is most important to biota? If we fix physical issues, will contaminants still keep biota down? 2) We need to know more about exactly how the hydrologic changes impact channel morphology and physical habitat. This, obviously includes sediment inputs increasing (from development runoff) and decreasing (since we've paved everything, do upland sediment inputs actually decrease?), and sediment from channel erosion (downcutting and widening). Based on past research, we know quite a bit about the impacts of urbanization on rivers and streams. Of particular interest to me - urbanization drastically changes watershed hydrology, sediment production and, eventually, channel morphology (enlargement). Unfortunately, there is still much we don't know. We don't know the rates and timing of channel change. We don't know how long it will take for the stream channels to stop enlarging and reach a new steady state (or if they in fact do). Both of these questions need to be answered in order to-- 1) inform urban stream restoration design (When should we do the restoration?; and What should the new steady state channel look like?); and 2) to fully understand sediment dynamics (When will the channel stop enlarging and, thereby, seize to be a source of sediment production from bank/bed erosion?).3) Finally, how do urbanization/hydrologic/morphologic changes translate into aquatic habitat changes? By habitat, I'm talking about flows, hydraulics, substrate, and bed stability issues that matter to fish and macroinvertebrates. If we can understand how the habitat has changed for the worse, perhaps we can do "restoration" to improve habitat, even though we can't get rid of the impervious surfaces. Can these impacts be mitigated by conserving/restoring wetlands and forests, implementing stormwater treatment practices, etc.(and to what extent)? The chemical and biological impacts in different places and situations. 1. Ecoregional/provincial differences of urban impacts in terms of major drivers of biota and the generalized biotic response (i.e. which urban impacts are the most determinant to which organisms/processes, and where?). Along with this, teasing apart the different drivers to determine which ones are truly influential(and rank their importance)2. Effective and practical ways to reduce overland flow impacts in urban areas with current infrastucture (or minimal change in infrastucture). 3. Can (should?) urban stream communities and ecosystems be restored to some semblance of pre-urban conditions? If so, by what measures do we attain this? (IMO, just fixing what caused the problem will not necessarily make the system "return"). If not, what then is our target in terms of community structure and ecosystem function? How does this change with ecoregion? 4. Increased public knowledge and awareness of the issue. Restoration or development of best management practices to reduce or mitigate impacts of urbanization Development of unique management and regulatory criteria specific to low-gradient, urbanized streams (you can't expect them to live up to the standards of small headwater streams; how can you manage them more effectively, given certain physical/chemical/anthropogenic constraints?). I.e., what community structures or ecosystem services still exist, and how do we best protect them? Changes in benthic and fish assemblages; Nutrient processing; Urban stream restoration Erosion and sediment control - evaluate the engineering. How effective are practices in E and S manuel (green book) Stormwater management - evaluate engineering (how effective are BMPs in Bluebook)Can we economically capture and reuse stormwater How to retrofit problems from the past - stormwater quantity and quality are relatively new - can we retrofit to help solve problems of the past. A better understanding of the impacts of urbanization and various stormwater management strategies on the full stream hydrograph (i.e. not just peak and low flows) and how that influences aquatic ecosystems. The relative influences of changes in water quality, hydrology, instream hydraulics and sediment transport, and the food web on ecosystem integrity. The cumulative benefits of sound site and building design and innovative stormwater management, as compared to traditional designs (i.e. what is the least impact we will cause if we use the best development tools we have) at the (small) watershed scale. In addition to mechanisms, I think we need to think more about how human decisions, socioeconomics, and cultural perceptions influence urban ecosystems. The disconnect from watershed inhabitants and the watershed itself may exacerbate some of these problems, and until this is overcome how much of a difference can management alone really make? What are the long term responses of stream channels (dimensions) to changing hydrology? How do urban impacts propagate/attenuate through entire river networks? What is the long term response of terrestrial processes to urbanization, and how might changes in these influence streams in the future? Long-term affects of urbanization (heat islands) in relation to global climate change and associated changes in water-use / allocation patterns. i.e., balancing the water needs of a growing population while maintaining ecosystem integrity under scenarios of changing rainfall / runoff patterns. How do deal with spatial aspects of urban systems within stream/river networks. Coupling between water flow / water level (or lack thereof) and nutrient processing - e.g., stream component linkages (hyporheic, riparian, lateral retention zones). Urbanization and sediment movement (sediment availability a critical issue in coastal wetlands) How can urbanization take place with minimal impacts on streams? One thing that seems like it needs more synthesis is the biotic/geomorphic response patterns of conversion of lands to urban landscape from a prior impact such as agriculture uses, a better understanding of these types of systems is crucial for designing new studies and prescribing restoration efforts. The effects of multiple stressors. Urban streams may be subject to several impacts including "end of pipe" type and strom water runoff, relating ecological response may be difficult to pinpoint. More research is needed on effective adaptive watershed management, i.e. involving multiple disciplines, designed conceptual frameworks, selection of most appropriate monitoring activities. Will follow up Can we restore ecological functioning to streams impacted by urbanization and to what degree? For my area, it is: How does urbanization effect spring-fed river systems?
Disentangling cause and effect, so that corrective actions (stream restoration, riparian revegetation, detention ponds, etc) can have a high likelihood of achieving the desired outcome in the stream Threshold responses (physical, chemical, biological) to impervious surface. Evaluation of stormwater management practices. Partitioning contributions of various mechanisms of cumulative impact, e.g. hydrologic fluctuation, contaminants, thermal pollution, nutrient loading, etc. |
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