Stormwater treatment is commonly performed with a combination of approaches including the utilization of natural systems and engineered devices. Before using a proprietary treatment instrument it is required to verify its performance and efficiency in reducing different pollution components including the TSS. Different states have developed strategies and regulations for accepting new instruments. In this thesis the stormwater management plan of the City of Portland, Oregon(2008), is analyzed in order to improve the current regulations. These rules apply to new technologies which are proposed by vendors to be used in Portland's stormwater treatment plans. Each requirement which should be met by the applying vendors is thoroughly analyzed followed by a comparison with the Stormwater management plan(2008)regulations of the state of Washington the so called Technology Assessment Plan-Ecology TAPE (Howie, 2011). Because of the similarities in the climate and land use between these two testing frameworks in order to evaluate the potential applicability of data submitted by vendors who had devices approved by Washington, to be utilized by Portland. The treatment of total suspended solids (TSS) is the focus of this thesis since it is central to the testing process and since most of the other pollutions are attached to TSS and will get treated if TSS is treated. The overall analysis shows that Portland adopts more restrictive requirements on the characterization of stormwater event samples to be treated by a technological instrument while Washington's restriction are more stringent on the efficiency of total suspended solid removal, in which it demands higher standards on the treatment of TSS compared to Portland's efficiency requirements. In order to study practical context in which regulations are administrated by Portland, rainfall data from 66 gauges covering the period of 1980-2011 was studied and the impacts of seasonality, land use, land form, periods of no rain before and after an event and Portland's Modified Performance line on the number of accepted rain events were analyzed. The results which were accepted by state of Washington were also compared with the results accepted by the city of Portland on Portland's Standard Performance line. Our seasonality study suggests that Portland's requirements are unnecessarily restrictive which results in the disqualification of many otherwise useful stormwater events, sometimes allowing no natural events to be available for testing in dry years. The analysis of land use showed that land use has no statistically significant impact on the concentration levels of TSS, thereby indicating that land use restrictions in the testing rules could be usefully relaxed. Decreasing the interevent no-rain period significantly increases the total number of events providing sufficient data to assess the performance of treatment facilities. We also showed that many more events become suitable for performance testing if events separated by one hours or less are considered a single, longer event. Finally we identified a statistical relationship between number of forecasted accepted stormwater events and the total average daily precipitation in a given year.

Rain-on-snow (ROS) occurs when warm, wet air moves into latitudes and/or elevations having vulnerable snowpacks, where it can alter water inputs to infiltration, runoff and erosion. The Pacific Northwest is particularly susceptible: winter storms off the Pacific cause locally heavy rain plus snowmelt almost annually, and disastrous flooding and landsliding intermittently. In maritime mountainous terrain, the effects seem more likely and hydrologically important where warm rains and seasonal snowpacks are liable to coincide, in middle elevations. Several questions arise: (1) In the PNW, does ROS affect the long-term frequency and magnitude of water delivery to the ground, versus total precipitation (liquid and solid), during big storms? Where and how much? (2) If so, can we determine which elevations experience maximum hydrologic effects, the peak ROS zone? Probabilistic characteristics of ROS are difficult to establish because of geographic variability and sporadic occurrence: scattered stations and short observational records make quantitative frequency analysis difficult. These problems dictate a modeling approach, combining semi-random selection of storm properties with physical rules governing snow and water behavior during events. I created a simple computer program to perform Monte Carlo simulation of large storms over 1000 "years", generating realizations of snowpack and storm-weather conditions; in each event precipitation falls, snow accumulates and/or melts, and water moves to the ground. Frequency distributions are based on data from the Washington Cascades, and the model can be applied to specific sites or generalized elevations. Many of the data sets were based on observations at Stampede Pass, where high-quality measurements of weather and snow at the Cascade crest have been made since the 1940s. These data were used to inform the model, and to test its reliability with respect to the governing data distributions. In addition, data from ROS events at Stampede, and at research sites in southwest Oregon, were used to confirm that the model's deterministic calculations of snow accumulation, snowmelt, and percolation (yielding water available for runoff) adequately simulate conditions observed in the field. The Monte Carlo model was run for elevations ranging from 200 to 1500 m, each over a hypothetical millennium. Results indicate that the presence of snow in some storms reduces the amount of water reaching the ground. This occurred more often in highlands but also at middle and lower elevations, affecting the long-term frequency-magnitude relations across the landscape. In these conditions, the rain-gauges overestimate the amount of liquid water actually reaching the ground. For many storms, however, ROS enhances water reaching the ground, most significantly at elevations between ~500-1100 m. At lower and higher elevations, the water available for runoff exceeds precipitation in ~2% of events, but this proportion rises to ~20-30% at ~800 m. Other metrics (e.g., series statistics, exponential regression coefficients, frequency-magnitude factors) also indicate that this middle-elevation band (around ~800 m) experiences ROS most often and with greatest water available for runoff. Of the west-central Washington Cascades study region, about one-third to one-half the landscape is susceptible to significant ROS influence. These results indicate areas where ROS currently has the greatest hydrologic consequence on ecosystems and human works, and possibly the greatest sensitivity to changes in land-use and climate.

Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This thesis contains two manuscripts that respectively investigate the (1) initiation processes of debris flows in these glaciated catchments, and (2) debris flow occurrence and its effect on valley bottoms over the last thousand years. In a 2006 storm, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount Rainier. Gully heads at glacier termini and distributed collapse of gully walls imply that clear water was transformed to debris flow through progressive addition of sediment along gully lengths. In the first study, we analyze gully changes, reconstruct runoff conditions, and assess spatial distributions of debris flows to infer the processes and conditions necessary for debris flow initiation in glaciated catchments. Gully measurements suggest that sediment bulking requires steep gradients, abundant unstable material, and sufficient gully length. Reconstruction of runoff generated during the storm suggests that glaciers are important for generating the runoff necessary for debris flow initiation, particularly because infiltration capacities on glacial till covered surfaces well exceed measured rainfall rates. Runoff generation from glaciers and abundant loose debris at their termini explain why all debris flows in the storm initiated from proglacial areas. Proglacial areas that produced debris flows have steeper drainage networks with significantly higher elevations and lower drainage areas, suggesting that debris flows are associated with high elevation glaciers with relatively steep proglacial areas. This correlation reflects positive slope-elevation trends for the Mount Rainier volcano. An indirect effect of glacier change is thus the change in the distribution of ice-free slopes, which influence a basin’s debris flow potential. These findings have implications for projections of debris flow activity in basins experiencing glacier change. The second study uses a variety of dating techniques to reconstruct a chronology of debris flows in the Kautz Creek valley on the southwest flank of Mount Rainier (Washington). Dendrochronologic dating of growth disturbances combined with lichenometric techniques constrained five debris flow ages from 1712 to 1915 AD. We also estimated ages of three debris flows ranging in age from ca. 970 to 1661. Run-out distances served as a proxy for debris flow magnitude, and indicate that at least 11, 2, and 1 debris flow(s) have traveled at least 1, 3, and 5 km from the valley head, respectively since ca. 1650. Valley form reflects the frequency-magnitude relationship indicated by the chronology. In the upper, relatively steep valley, discrete debris flow snouts and secondary channels are abundant, suggesting a process of debris flow conveyance, channel plugging, and channel avulsion. The lower valley is characterized by relatively smooth surfaces, an absence of bouldery debris flow snouts, few secondary channels, and relatively old surface ages inferred from the presence of tephra layers. We infer that the lower valley is deposited on by relatively infrequent, large magnitude, low-yield strength debris flows like an event in 1947, which deposited wide, tabular lobes of debris outside of the main channel. Debris flows during the Little Ice Age (LIA) predominantly traveled no further than the upper valley. Stratigraphic evidence suggests that the main Kautz Creek channel was filled during the LIA, enhancing debris flow deposition on the valley surface and perhaps reducing run-out lengths. Diminished areas and gradients in front of glaciers during the LIA also likely contributed to decreased run-out lengths. These findings suggest that changes in debris flow source and depositional zones resulting from temperature and glacier cycles influence the magnitude and run-out distances of debris flows, and the dynamics of deposition in valley bottoms. / Graduation date: 2013

Modern cities are often perceived as the antithesis of nature; the built environment is understood as the transformation of raw and untamed nature into a rationalized human landscape. However, a variety of scholars since the nineteenth century have noted the persistence of nature in cities, not only in providing essential services but also resisting human control. Most recently, urban geographers and environmental historians have argued that processes of urbanization do not entail the replacement of natural with artificial environments, but are more accurately understood as a reconfiguration of human/nature relations. In this dissertation, I employ this relational perspective to study a specific form of urban nature: stormwater flows. Urban drainage or stormwater management activities in US cities are a vivid example of the tensions between nature, society, and technology. In this study, I present a comparative case study of two US cities--Austin, Texas and Seattle, Washington--where stormwater issues have been a central focus of public debate over the last four decades. Using textual analysis, in-depth interviews, and experiential research methods, I argue that stormwater management practices involve not only the rational management of technological networks but also implicate a wide range of seemingly unrelated issues, such as local governance, environmental protection, land use decisionmaking, community development, aesthetics, and social equity. To describe the relational implications of urban nature, I present a framework of ecological politics to characterize drainage activities as rational, populist, or civic. I argue that the latter form of politics has the greatest potential to relieve the tensions between urban residents and their material surroundings by embracing a systems perspective of human/nonhuman relations and engaging local residents in the hands-on management of environmental flows. It is through the development of deliberative and grounded forms of civic politics that urban residents can forge new relationships between technology and nature, and in the process, understand their place in the world. / text