Condition of 1882 Santa Margarita River Railroad Bench in Temecula Canyon in 2001


Introduction
Data
Analysis


Introduction

In 1882, a bench ~16' (?) wide was constructed along the banks of the Santa Margarita River in Temecula Canyon for the railroad tracks from Fallbrook to Temecula. This was a remarkable feat for the time, accomplished by "hundreds of Chinese coolies". The Gorge is narrow, with walls that are nearly vertical in places, and the route required ~4 crossings of the river in the 5 miles of the Gorge. For the history of the railroad, see The Fallbrook Line and Perris and its Railroad.

The bench was constructed far too close to the River, typically ~25' above the bottom of the Canyon, and hence has been subjected to flooding events where the water reaches the top of the bench. Washouts of 30 miles of track occurred in 1884, which was repaired later that year. In 1891, washouts caused the abandonment of this segment of track.

We have begun a project to measure the precise locations of the remaining segments of the bench and note their condition. Analysis of these data will reveal the extent of erosion along the banks of the Santa Margarita River over a period of ~110 years. The erosion will be correlated with location of the benches relative to bends in the river and distance downstream, along with any other variables discovered to be significant.

These data will also serve as a benchmark for measurements of erosion in the future.

Significantly, this location is essentially natural, without significant development along the River. Further, flows in the river are also essentially natural, without major dams upstream that disturb the natural flow of water. Hence these measurements will reflect the "natural" rate of erosion in similar systems. They can thus serve as a baseline to compare erosion measurements elsewhere in areas that have been significantly modified by humans.

Finally, these measurements of the surviving railroad bench will be of interest to historians interested in such remnants of the past.


Data

An initial survey of the location and condition of the remaining benches was done on 3 January 2001 by Tom Chester, Jim Jenks, John Hogan, Carline (Luke?), Claudia Luke, Carl Nelson and Mark VanScoy. We hiked along the Gorge from just above the Via Tornado Crossing to the remaining Railroad Trestle, and recorded the location and condition of the remaining benches.

Note that the Santa Margarita Ecological Reserve is not open to the public, and is open to researchers only after approval of their research program by SDSU. Furthermore, there is no trail along the Gorge and considerable poison oak is present, including many unrecognizable broken branches of dormant poison oak in debris. Several of us, who were never previously allergic to poison oak, came down with cases of poison oak from this and previous trips, all in the cause of Science!

Table 1 presents the raw data, tagged by "river mile" measured along the bench from the beginning of the Santa Margarita River at the junction of Murrieta and Temecula Creeks. The river mileage for the first point is the approximate mileage along the river to the point in the river closest to the beginning of this survey. Most of the subsequent mileages below are the straight-line distance from the previous point. A few of the mileages were calculated using intermediate points following the river trend, and hence are slightly longer than would be calculated using the straight-line distance from the previous point.

Latitude and Longitude coordinates are in the NAD27 datum, and were measured using a Garmin Etrex receiver, which typically quoted an error of 30-40', presumably a 95% confidence error, for most of the measurements.

Table 1

River MileageLatitudeLongitudeComments
2.18033.45669-117.16752Begin survey. Bench begins after small side canyon had cut away bench in its side canyon.
2.19233.45664-117.16771Bench is somewhat protected by rock on river side. The cut here measures 17' between rock walls. The minimum width of the bench is 12' (due to erosion). The bench is 20-25' above the river.
2.22033.45642-117.16812Begin rockfall on bench.
2.22333.45640-117.16817End rockfall on bench.
2.29533.45594-117.16929Bench ends at Via Tornado Road. Road and Aqueduct construction may have removed bench here.
2.34333.45560-117.17000Via Tornado and Second Aqueduct crosses River (position estimated, not measured). First aqueduct still downstream.
2.43533.45497-117.17140Begin bench, with only solid rock left (fill on top of solid rock is gone).
2.47033.45455-117.17173Bench is 15' above river.
2.48133.45440-117.17177End bench
2.53333.45379-117.17221Large rockfall from overhang above probable bench location
2.54133.45370-117.17230Approximate end of rockfall.
2.57133.45334-117.17259Bench reappears, with only solid rock left (fill on top is gone)
2.62433.45271-117.17312End most traces of bench
2.66733.45227-117.17363Begin bench. 30' above river, 5' at narrowest, 8' at largest
2.71133.45188-117.17424Bench continues, but path goes down to river since bench is overgrown with vegetation
2.80033.45083-117.17509Still below bench - stacked boulders above us to support side of bench.
2.89633.44947-117.17543Just past RR crossing of a side stream, ~6' (?) gap, lined with rocks on both sides of the side stream. Bench ~10' above water.
2.93533.44892-117.17558Guess at end of bench (not recorded)
2.99033.44856-117.17637East end of cut in cliffside for rr, after crossing river. (Rock on both sides of cut)
3.02133.44852-117.17690West end of cut in cliffside. Train crosses again after this. Approximate location of picture 11126.
3.08933.44890-117.17791Start edge of bench on other side of river.
3.12633.44901-117.17854~35' east from top of trestle
3.13433.44905-117.17867Trestle. End survey.

A rough understanding of the overall condition of the bench can be obtained by classifying each section using the categories in Table 2, and computing the total length in each category. Table 2 gives the percentage of the 0.95 miles surveyed that falls into each category. In addition, each category is assigned a line type and color, in order to graphically show the condition of the bench vs. location.

Condition of BenchPercent of Surveyed Mileage in CategoryAssigned Line Type and Color for PlotAssigned Numeric Value for Plot
Good43Solid, Pink1.0
Bench eroded to less than 8' in width5Solid, Rose0.7
Bench has only its solid rock foundation, with its top fill removed32Solid, Tan0.9
Bench is covered with rockfall1Solid, White1.1
Bench is gone10Dashed, Gray0.5

The bench is missing, or heavily eroded, along only 15% of its length surveyed here.

The numeric value is used to illustrate the condition of the bench vs. river mileage (Figure 1). This plot shows at a glance that the bench is largely intact for the short distance above the Via Tornado River Crossing at mile 2.3, as well as from mile 2.7 to the trestle at mile 3.1, except for the missing river crossing segments. Between mile 2.3 and 2.7, the bench is either significantly eroded, or missing.

Figure 2 shows a map of this entire segment. The eroded segment from mile 2.3 to 2.7 corresponds to the outside bank of the river as it curves slightly to its right, whereas the intact segments correspond to the inside bank of the river. The eroded segment from mile 2.3 to 2.7 corresponds to where the river is straight, although this first part of this segment is the portion modified by road and aqueduct construction.

The following maps show in finer detail the individual segments:


Analysis

(Section TBS after more data are taken)

We speculate that the bench was typically ~16' wide, since we measured a 17' distance between rock walls at one cut along the route.


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Copyright © 2001 by Tom Chester, Jim Jenks, Claudia Luke, Carl Nelson, Mark VanScoy, and John Hogan.
This is a private webpage solely for the use of the docents
http://tchester.org/sd/places/smer/docents/rrbench/index.html
Comments and feedback: Tom Chester
Updated 6 January 2001