DEPLOYMENT OF CURRENT METERS AND/OR SEDIMENT LOAD SAMPLERS DURING HIGH-STAGE STREAM FLOWS IN FIELD SITES REQUIRING LEAVE NO TRACE AND SHORT-TERM OR SAME-DAY SETUP AND REMOVAL OF INSTRUMENTATION: PRELIMINARY RESULTS FROM A PORTABLE CABLEWAY SYSTEM USED AT JOHNSTOWN FLOOD NATIONAL MEMORIAL

Measurements of stream discharge or sediment load that can be readily obtained in streams with current meters and samplers during lower flows via wading methods, can pose significant logistical, safety, and budgetary hurdles during high-stage intervals. In unwadeable streams, a common approach is to use a cable system to ferry instrumentation across and into the stream (Turnipseed and Sauer, 2010). Nearly all of the commonly used systems and those in the literature require emplacement of poles, cables, and systems that remain on-site, typically for years. Other systems, designated as portable, are often intended for deployment of several months and tend to cost multiple thousands of dollars when sounding reels are included (Paradiso, 2000).

We give a schematic for workers to construct their own portable, lightweight cableway system that can be easily and inexpensively assembled from commonly available materials. Considerable cost savings are realized by replacing a sounding reel with a winch and handline. The system is suitable for sites in which it is not desirable to leave instrumentation on-site due to leave no trace requirements, security concerns, or only periodic data collection. System weight is 42 kg and no component exceeds 20 kg. It can be readily portered by two persons to remote or rugged sites. The system can be used to deploy sediment samplers (e.g. US BL-84) and/or current meters following standard methods (e.g. Gray et al., 2010).

The cableway has been tested and deployed at the Johnstown Flood National Memorial as part of a study to gauge the South Fork, Little Conemaugh River at the historical abutment of the former South Fork Dam, which failed in 1889 killing more than 2,200 people. To date, no modern empirical study has been performed on the watershed that fed the reservoir. The stream is unsafe to wade following moderate precipitation events and NPS regulations require leave no trace. The site is accessed by a moderately steep (10 percent slope), grassy 200 meter trail. Cableway setup times averaged 50-75 minutes and disassembly 40-60 minutes. Total on-site times were 4-5 hours when collecting a discharge measurement. Low-stage data collected via the cableway (with AA meter) fit well on the stream rating curve constructed by wading and pygmy meter data and fall well within the 95% prediction interval.