Category Archives: Individual Movement

Crossing Rivers and Canals

MC1 Peter Lewis

MC1 Peter Lewis

10/10/14
To Do Today:

  • PT – Cardio – 1hr Swim // Strength – Leg group
  • Friday rules in effect 1730

Rivers and Canals

A river is a large, natural stream of water that empties into a larger body of water. The slope of the riverbed and the volume of water in the river determine its current. Canals resemble small rivers or streams in their width and depth, but usually lack any significant current. Climbing out of these waterways can be difficult if the canal is flanked by steep banks.

Fording

A ford is any site in a river, stream, or canal where the water is shallow enough for people or vehicles to cross without using flotation devices. Canal bottoms are usually too soft to support fording vehicles, and waders frequently stumble. The tactical situation dictates the  location of the fording site. Seek fords that are protected from enemy observation and that allow for adequate supporting fires if available. A night fording takes at least one and a half times as long as a daylight fording. The term “river” refers to rivers, streams, and canals.

The following table identifies desirable fording characteristics:

  • Concealment. The ford hides personnel and vehicle movement from enemy observation.
  • Accessibility. The ford should have low banks with gentle gradients. This allows a free flow of traffic at both the entrance and the exit.
  • Slow Current. The fords current should not exceed 1.5 meters per second if possible.
  • Firm Footing. The ford’s bottom, entry, and exit composition should be firm enough to support  traffic. Do not drive a vehicle over any bottom composition that a 2-inch diameter stick can be pressed into more than 1 or 2 inches.
  • Gently Sloped Channels. The ford’s entry and exit points should be gently sloped. If possible, locate a  portion of the stream where the channel is not actively shifting.
  • Depth. The fording depth is less than or equal to the least capable vehicle.

Determine Waterway Slope

Units move into and out of water faster and more quietly if entry and exit points are not steep or muddy. Slope is the amount of change in ground horizontal distance (run) and in vertical elevation (rise) from one point to another. Slope is usually expressed as a percentage. You can use a clinometer, map, or line of sight and pace to measure the percentage of a slope.

  • Map. A map measures the horizontal distance along a desired path. Determine the difference in elevation between the path’s starting and ending points. From a map’s scale, you can determine the distance between two points. From a map’s elevation lines, you can determine the difference in height between the same two points. Both figures must be in the same unit of measure (e.g., feet, meter). Divide the elevation (rise) by the distance (run) and multiply by 100.

map

  • Line of Sight and Pace. To determine line of site and pace, stand at the bottom of the slope, keep your eyes level, pick a spot on the slope, then pace the distance. The number of paces  multiplied by a standard measure of 0.75 meter determines the run. The eye-level height (usually1.5 to 1.7 meters) determines the rise. Repeat this procedure until you have covered the entire distance you want to measure for each spot (vertical and horizontal). Add the vertical distances to provide total rise and the horizontal distances to provide total run.

Determine Current Speed

Current speed increases as channels narrow. It may be necessary to locate a wider ford location to obtain a slower stream current. The following steps are used to calculate the speed of the current:map2

  • Determine points A and B along a channel. Then measure the distance between those two points.
  • Sight directly across the water from points A and B to locate points C and D.
  • Throw a floating object (e.g., a stick) upstream from points A and C. Observe the object as it floats toward points B and D.
  • Subtract to find the time it takes for the object to float from start to finish.

Do not attempt to swim across currents unassisted that are moving faster than 1.5 meters per second. Equivalents of this speed include:

  • Quick-time march rate of 120 counts per minute with one, 30-inch step at each count.
  • 5 feet per second.
  • 3.5 miles per hour.
  • 5.5 kilometers per hour.

Measure Waterway Width

A river’s width can be estimated from the width of its symbol on a scaled topographic map. If this is not possible, use the following compass techniques:map3

  • Stand at the water line (A).
  • Shoot an azimuth to a point on the opposite bank (B).
  • Move upstream or downstream until you are at a point (C) where you can shoot an azimuth 45 degrees larger or smaller than the original azimuth.
  • Measure the distance between points A and C. The distance calculated equals the river’s width.

Calculate Downstream Drift

A river’s current will cause personnel and equipment to drift down-stream. If personnel and equipment are aimed straight across the river, they will sideslip downstream as they move across the current to the other shore. Therefore crossings must compensate for the effects of a river’s current. Water entry is usually made upstream of the desired exit point. Use the formula below to calculate downstream drift:

map4NOTE: The crossing speed for a swimmer across a river may vary but is generally limited to 1 meter per second. All measurements must be in the same unit of measure (e.g., meters, feet).

The Buddy System

Whenever you must enter into or operate on the water, a “buddy system” should be employed in which each swimmer is paired with another. The buddy system matches an experienced swimmer with a weak swimmer. The experienced swimmer assists and encourages the weaker swimmer and bolsters confidence during night crossings. If a group has an odd number of swimmers, place the extra person with another pair to form a three person team.

Care of Weapons

Most modern weapons and munitions are designed to be able to operate after immersion. However, protect your weapons from moisture whenever possible. A gas-operated weapon can malfunction if water travels down the barrel and enters the gas tube. To protect the gas tube:

  • Close the weapon’s bolt before entering the water.
  • Seal the muzzle with a condom, balloon, plastic spoon wrapper, or other form of waterproof material.
  • Tie or melt the protective cover to create a watertight seal.

When the muzzle’s protective cover is no longer needed, remove it. Open the bolt and inspect the barrel. If the tactical situation permits, swab excess moisture from the barrel. Test fire automatic weapons, if possible. Field strip and clean weapons as soon as possible. If time does not allow for a complete inspection, rinse inaccessible areas with small amounts of diesel fuel, then dry.


 

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