Channel Migration and Avulsion Hazards at Sunshine Point Campground, Mount Rainier National Park, Washington

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.

Ultrasound Mapping of Stimulated Finger Flexion During Infra-Clavicular Brachial Plexus Nerve Blockade for Elbow Arthroplasty and Its Correlation To Postoperative Analgesia

Background: Infraclavicular brachial plexus nerve blockade (ICNB) is a very common anesthetic procedure performed for upper extremity surgery at the elbow and distally, however the rate of adequate analgesia is variable among patients. Ultrasound guidance (US) has not been demonstrated to increase the success rate of ICNB when compared to nerve stimulator (NS) guidance. Combined US and NS guided ICNB have not been reported, although there is a call for more trials comparing the two techniques. This study was performed to observe if a specific anatomic region near the axillary artery of the brachial plexus identified by finger flexion with nerve stimulation results in improved postoperative analgesia. Method: Patients undergoing elective elbow arthroplasty received a postoperative ICNB. The angle of the nerve stimulator needle tip and the radial distance from the center of the arterial lumen at which an optimal finger flexion twitch response was observed were measured with ultrasound imaging. Pain scores and postoperative opioid dosages on discharge from the post anesthesia care unit and at 24 hours after surgery were recorded. Results: 11 patients enrolled in this study. Adequate finger flexion response to nerve stimulation that resulted in complete analgesia was more frequently observed when the needle was located in the postero-superior quadrant in relation to the axillary artery. Identifying a specific point near the brachial plexus in relation to the artery that consistently provides superior analgesia is desirable and would lead to improved analgesia and faster onset time of nerve blockade and would reduce the need for other approaches for brachial plexus blockade with their associated disadvantages.