Editing Log flume (section)

==Flume construction==
[[File:High-Trestle-Sanger-Flume.jpg|thumb|The high trestle on the Sanger Flume was over {{convert|300|ft}} tall.<ref name="Valley Flumes">{{cite news |author=<!--not stated--> |date= |title=A look back at the history of the Valley's log flumes |url=https://abc30.com/sierra-nevada-central-valley-fresno-county/56206/ |work=ABC 30 (KFSN) |location=Fresno, California |access-date=November 19, 2022}}</ref>]]
Flume routes were surveyed by engineers using the same methods as a railroad survey. However, flumes had several advantages to logging railroads in steep terrain. They could span [[gulch]]es using much lighter trestles and they took up less space, fitting inside narrower canyons where there wasn’t room for a railroad. The main disadvantage of the light construction was they were damaged more easily by fire, floods, wind, and falling timber. But they could be repaired more cheaply.<ref name="Logging Principles" />{{rp|394}}

Flume sites were mostly in rough, undeveloped wilderness. Unlike railroad construction, this required lumber and supplies to be carried in by hand. Flume boxes and trestles were built onsite. Construction crews included six to eight workers. On trestles, four worked aloft continuously. One low man handled and sent up the lumber.

Working on the flume was a dangerous job. [[Occupational fatality]] statistics are unavailable. But reports suggest that falls resulted in many injuries and deaths.<ref name="Valley Flumes" />

Square lumber was often provided by a temporary, portable sawmill erected at the head of the flume. Other times, round timber trestles of {{convert|8|in|cm}} to {{convert|12|in|cm}} diameter were cut and finished from along the route.

Some trestles achieved staggering heights to maintain a desirable grade. Three percent was ideal for a straight flume. Sometimes grades of up to 75 percent were used on short stretches. The steeper the grade the more gradual the curves had to be, or else lumber would jam or go over the sides. The maximum curve was 8 degrees.<ref name="Logging Principles" />{{rp|395–396}}

===Box flumes===
[[File:Log Flume Box Cross Section Box for Small Logs.jpg|thumb|Flume box cross section.]]
Early logging flumes were square wooden chutes known as box flumes. These were prone to jams that could cause damage and required constant maintenance. They were also costly to build. A square box carries much more water compared to a V-shaped flume. The greater weight of the water required a sturdier structure, especially heavier trestles.<ref name="Logging Principles" />{{rp|399}}

===V-flumes===
In 1867, James W. Haines first built the V-shaped log flumes that allowed a jammed log to free itself as the rising water level in the flume pushed it up. These efficient flumes consisted of two boards, {{convert|2|ft|m}} wide and {{convert|16|ft|m}} feet long, joined perpendicularly, and came in common use in the western United States during the late 19th century.<ref>{{cite book |last=Fregulia |first=Carolyn |date=2008 |title=Logging in the Central Sierra |location= |publisher=Arcadia Publishing |page=50 |isbn=978-0-7385-5816-5}}</ref>

Box flumes were not made obsolete. They continued to be built when a large volume of water was desired for a secondary use, such as irrigation. Box flumes were also more capable of handling materials uneven in size and weight simultaneously. Lumber, [[pulpwood]], shingle bolts, and whole logs move at different speeds and were prone to double-up in a V-flume’s low grades and curves. Finally, box flumes could move an unprecedented amount of material, up to a maximum capacity of {{convert|300000|board feet|m3}}, or three times as great as the maximum for a V-flume.<ref name="Logging Principles" />{{rp|400}}

<gallery mode=packed heights=120px>
Log Flume Cross Section V-Box.jpg|V-Box flume cross-section for large logs.
Log-Flume-Cross-Section-V-Box-for-Lumber.jpg|V-Box flume cross-section for lumber.
Madera Sugar Pine Flume.jpg|Water flowing down a V-flume near [[Madera Sugar Pine Company|Sugar Pine, California]].
Madera Sugar Pine Company China Store Flume Trestle.jpg|A tall V-flume trestle around 1900.
</gallery>