2 resultados para Critical point
em University of Washington
Resumo:
In November 2006, the flood of record on the upper Nisqually River destroyed part of Sunshine Point Campground in Mount Rainier National Park, Washington. The Nisqually River migrated north and reoccupied five acres of its floodplain; Tahoma Creek partially avulsed into the west floodplain, topping banks of an undersized channel and flooding the campground. I assessed hazards to infrastructure at the old campground location, where the Park proposes to rebuild the remaining campground roads and sites. This assessment focuses on two major hazards: northward Nisqually River migration, which may reincorporate the floodplain into the river destroying infrastructure; and Tahoma Creek avulsions, which may flood the campgroud and deposit sediment burying campground infrastructure. I quantify northward migration by: estimating migration rates and changes to channel width; evaluating river occupation of the pre- and post-2006 campground; and estimating scour depths at revetments protecting the campground. I digitized the Nisqually River channels and channel centerlines from maps and images between 1955 and 2013 into a GIS, which I used to estimate migration rate and river width changes. Centerline migration rates average 9 ft/yr along the length of the Nisqually River study reach; at Sunshine Point lateral migration rates average 11 ft/yr. Maximum migration along the study reach was 19 ft/yr between 2006 and 2009. Greater than average migration rates and channel widths correspond to river confluences and include the Tahoma Creek confluence at Sunshine Point. To determine historical channel locations and the frequency that the river occupied different parts of its floodplain, I digitized the river from maps and images between 1903 and 2013. The Nisqually River flows through Sunshine Point Campground in eight out of 15 historical images. I assess scour at revetments protecting infrastructure from the Nisqually River during a 100-year recurrence interval flood using measured cross-sections. During a 100-year flood, the Nisqually River may scour up to 10 feet below the bed elevation. These scour depths can destabilize critical revetments leaving loose unconsolidated riverbanks exposed to Nisqually River flows. To determine the causes, locations, and frequency of flood hazards from Tahoma Creek avulsions, I field map avulsion channels and compare the results with imagery and channel width changes between 1955 and 2013. Mapped avulsion channels occur with swaths of dead vegetation or nascent vegetation; both dead and recent vegetation are visibly distinct from surrounding vegetation in aerial images. Times of changes to these vegetation anomalies correspond to increases in Tahoma Creek channel width. Avulsions have occurred at least three times in the study period: pre-1955, between 1979 and 1984, and in 2006. The 1984 and 2006 avulsions both occur after increases in Tahoma Creek reach averaged width. The NPS is considering two options to rebuild Sunshine Point Campground, both at the same location. The hazards posed by the Nisqually River and Tahoma Creek at Sunshine Point will affect both construction options equally. Migration hazards to the campground may be reduced by limiting the proposed campground infrastructure to an elevated ridge that has not been occupied by the Nisqually River since 1903. The hazards of damage from migration may be reduced by revetments, which were effective in preventing northward Nisqually River migration in 1959 and 1965. Tahoma Creek avulsions are related increased of Tahoma Creek reach averaged widths, which are near a 58- year maximum, and occurred during a 10-year flood in 1984. The campground may be as susceptible to flooding from avulsions during as little as a 10-year flood. A large avulsion may occur with the next significant Tahoma Creek width increase. Glacial retreat has been shown to increase debris flow activity and increase sediment delivery to Mount Rainier rivers. Increased sediment discharge has been correlated with aggradation, which will further encourage Tahoma Creek avulsions.
Resumo:
Ethos is the spirit that motivates ideas and practices. When we talk casually about the ethos of a town, state, or country we are describing the fundamental or at least underlying rationale for action, as we see it. Ideology is a way of looking at things.It is the set of ideas that constitute one’s goals, expectations, and actions. In this brief essay I want to create a space where we might talk about the ethos and ideology in knowledge organization from a particular point of view; combining ideas and inspiration from the Arts and Crafts movement of the early Twentieth Century, critical theory in extant knowledge organization work, the work of Slavoj Žižek, and the work of Thich Nhat Hahn on Engaged Buddhism.I will expand more below, but we can say here and now that there are many open questions about ethos and ideology in and of knowledge organization, both its practice and products. Many of them in classification, positioned as they are around identity politics of race, gender, and other marginalized groups, ask the classificationist to be mindful of the choice of terms and relationships between terms. From this work we understand that race and gender requires special consideration, which manifests as a particular concern for the form of representation inside extant schemes. Even with these advances in our understanding there are still other categories about which we must make decisions and take action. For example, there are ethical decisions about fiduciary resource allocation, political decisions about standards adoption, and even broader zeitgeist considerations like the question of Fordist conceptions (Day, 2001; Tennis 2006) of the mechanics of description and representation present in much of today’s practice.Just as taking action in a particular way is an ethical concern, so too is avoiding a lack of action. Scholars in Knowledge Organization have also looked at the absence of what we might call right action in the context of cataloguing and classification. This leads to some problems above, and hints at larger ethical concerns of watching a subtle semantic violence go on without intervention (Bowker and Star, 2001; Bade 2006).The problem is not to act or not act, but how to act or not act in an ethical way, or at least with ethical considerations. The action advocated by an ethical consideration for knowledge organization is an engaged one, and it is here where we can take a nod from contemporary ethical theory advanced by Engaged Buddhism. In this context we can see the manifestation of fourteen precepts that guide ethical action, and warn against lack of action.