Swale in Cross section

I went in search of topographic maps that might help me answer two questions: what could the confederate soldier see, and how much protection did a union soldier have if he were in the swale?  Online, I found fairly modern standard US Geological Survey maps with a ten-foot contour interval. These had various dates, some back to the 1930’s. While this was a start, it certainly was not conclusive nor detailed enough to analyze. There would be no way to tell if there was a dip or was the slope constant between the 60 and 70 foot contours?

At the Fredericksburg City Engineering Department, I found five-foot contour mapping dating from the 1990’s.  This was more helpful, but was there anything more detailed available? Finally, with the assistance of the Planning Department and Graphics, I discovered digitized two-foot contour mapping.  Something I could use in my quest to answer “what could the confederate soldier see?”  This is available on the City of Fredericksburg website at;

 http://fredericksburgva.gov/index.aspx?NID=515

Using this Geographic Information System (GIS) data, I then decided to create several cross sections of the terrain. It seemed best to use the existing roads and alleys matching my photographs, a total of six in all. All of them start at the Sunken Road, where the confederate soldier stood. Only Mercer Street actually shows a complete unobstructed view.  The remaining five views are blocked by trees within the National Military Park and then by two continuous rows of houses between Willis and Shepherd Streets.

Considerations.

First, the average soldier in the Civil War is reported to have been 5 foot 7 inches tall. Some online sources say 5 foot 8-1/4 inches tall is more correct. For additional information see: http://www.historynet.com/civil-war-soldiers, or http://www.civilwarhome.com/themen.htm, or http://hubpages.com/hub/Myths-and-misconceptions-about-history-people-were-shorter-back-then. From this, I derive that his line of sight starts with him standing on the Sunken Road. His rifle is 5 feet above the ground to keep things simple.

Second, Marye’s Heights slowly pulls back away from the city, as one goes south. The distance from the Sunken Road, located at the bottom of the slope of the heights, and Littlepage Street also increases. The distance is 225 yards at Mercer Street and approximately 300 yards at Lafayette. This is a small but noticeable increase in range and could possibly decrease accuracy of a rifleman in the heat of battle.

Third, as described by both confederate and union participants, just beyond Littlepage Street, the land dips or falls off. From that point where the swale begins until the land again comes back into the field of vision, some or all of a union soldier might remain hidden from view. This area is known as being in defilade. How much protection was provided by this defilade remains to be seen.  For the union soldier, at a minimum, he needed enough vertical height in defilade to be out of the line of sight. This, hopefully, with sufficient vertical freedom to enable him to roll over and maybe crawl or walk, even if in a crouch, laterally along the Swale while remaining in defilade. Obviously at some point he might break the plane of the line of sight and be in the vision of the confederate soldier.  For additional information, see;  http://usmilitary.about.com/od/glossarytermsd/g/defilade.htm.

Fourth, urban development of the area in and surrounding Mercer Square occurred in an era before modern times when bulldozers substantially altered the terrain. This is important in an attempt to “see” the terrain as it was in 1862. The sooner a particular parcel of land was developed following the civil war, the more likely its relative elevation would resemble what it was like in 1862.

Cross-Section-Map-cropped-wMap of the cross sections

The six cross sections from north to south are as follows:

Mercer-St-CS#1-webMercer Street & Littlepage – Cross-section #1

Haw-St-and-Alley-CS#2-webHaw Street & Alley – Cross-section #2

Charlotte-St-CS#3-webCharlotte Street & Littlepage – Cross-section #3

Charlotte_Wolfe-Alley-CS#4-webAlley between Charlotte and Wolfe  – Cross-section #4

Wolfe-St-CS#5-web Wolfe Street and Littlepage – Cross-section #5

Wolfe_Lafayette-Alley-CS#6-web Alley between Lafayette and Wolfe – Cross-section #6

My term Zone of Protection is used to indicate the area in which a union soldier might not be seen.  I measured the area in which a soldier in defilade might hide.  I ignore for the time being the fact that a person has depth, so each side of the zone is suspect.  Given that no one is one inch thick, one’s head and upper body would need more space in which to stay hidden than ones legs or feet.

The elevation along the Sunken Road also varies.  At the junction of Mercer Street and the Sunken Road the elevation today is 94 feet. The confederate soldier’s eye would be at 94 plus 5 feet or approximately 99 feet of elevation. The lip of the swale on Mercer Street closest to the Sunken Road is approximately 74 feet of elevation. Where the soldier’s line of sight strikes the terrain on the far side of the zone of protection is at an elevation of approximately 68 feet. The distance in defilade in the zone of protection is about 180 feet. This ignores the fact that on Mercer Street, the roadway is built up, making today’s actual depth available to hide questionable. What would it have looked like in its unimproved condition in 1862? The distance from the Sunken Road to the closest lip of the swale is approximately 700 feet or 230 yards.

At the second cross-section identified as Haw Street and Alley, the swale is quite enlarged when compared with that along Mercer Street and so on along each different cross-section.  The critical measurements with this preliminary investigation are summarized in the following table:

  1. Swale-Cross-Section-dataMy findings to this point are;The swale does exist.
  2. The swale most likely provided some defilade protection for union soldiers
  3. This being true, a significant number of union lives were probably saved during the battle due to the swale. They had some place to hide.

In the next blog, I will put photos and the topography together.

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About Peter Glyer

I am retired with a lifelong interest in history, primarily the Civil War and WWII - Europe. I was an Army engineer, hence my interest in terrain. I graduated with a degree in City and Regional Planning and a Masters in International Relations.
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