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5309Walking distance clarifications [was Re: Living in the desert]

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  • Ariel L. Szczupak
    Jun 5, 2007
      It seems from some offlist messages that my laconic numbers spread
      across several message didn't form a comprehensive picture. I'll try
      to correct that.

      First I should mention that the average numbers for walking distance
      per hour or per day are not desert specific. They are average
      numbers, and as such they average the conditions too. They depend
      more on human physiology than on topography or climate.

      Example: Walking a level path in central Sinai in July will be
      significantly harder than walking a much less level path along the
      top of the central mountain range in Canaan (e.g. Jerusalem to
      Shechem or Hebron). The situation will be reversed in April - the
      Sinai walk will be pleasant while the mountain walk will be through
      thick spring vegetation (no paved roads before the Romans). And the
      July walk in Sinai will be significantly easier than a July walk on a
      level path from Tiberias to Dan, because while the temperatures will
      be in the same range, the high humidity in the upper Jordan basin
      will increase the "heat factor" significantly.

      A normal person will average in non extreme conditions 5 km/h and
      will be able to go on indefinitely walking at such a speed for 10
      hours a day carrying a light load (I think the figure for the load is
      up to 20 kg). So the expression "a day's distance" or "a day's walk"
      usually means (when it doesn't have a defined meaning for a specific
      context) about 50 km (roughly 30 miles).

      It may seem strange that this average speed works for most climates.
      It seems obvious that walking a level path in a very hot desert is
      much harder than walking a similar path in e.g. Holland. But when you
      walk in the desert you'll split the 10 hours to the morning and
      afternoon-evening and rest in the middle of the day - you'll still
      get the same 10 hours of walking.

      A specific context for which there is another figure is a large
      infantry force, meaning hundreds or thousands or people with heavy
      loads. The figure, from various armies across various periods and
      geographical areas, is around 25 km/day. The more people you have the
      wider the fitness range will be and the slowest person determines the
      overall speed. The load carried by each person is significantly
      heavier. Unless the route conditions are extremely favorable, such a
      group will proceed as a single file column and the overall time will
      be from the moment the first person leaves until the moment the last
      person arrives. Etc.

      At the other end of the distance-per-day range are "elite" walkers,
      e.g. commandos. They can reach 100km/day. They do it both by walking
      slightly faster (averaging maybe 6-7 km/h) and especially by walking
      more hours per day. 16 hours per day at 6km/h is 96 km. This however
      is not a speed that can be maintained indefinitely.

      When a walking party includes pack animals it slows down and the
      figure is about 25 km/day. Again it's an average and a lot will
      depend on which animals are used. Humans are much more adaptable to
      various terrain and weather conditions than pack animals - a donkey
      is not adapted to sandy dunes and a camel is not adapted to mountain
      passes. Caravans will be slower, but they won't need more watering
      spots than a group of only humans walking at 50 km/day. The pack
      animals can carry significantly more water than a person so that both
      people and animals can proceed with watering stops every two days.

      So for people-only and for caravans the distance between watering
      "pit stops" that determines if a desert can be crossed is about 50km.

      [Again, it's an average figure, a general indicator, that has to be
      adapted to the specifics of each case. It shouldn't be used as a
      magic number. For example walking dune "waves" length-wise is within
      normal walking conditions but crossing those same dunes, i.e.
      climbing dunes up and down, would be extreme walking conditions. It's
      the same terrain, but the direction in which it is crossed will
      determine the distance per day. When you look at a map it will be
      obvious if the path is along a mountain ridge or crosses it, but a
      map might fool you to think that crossing a dune area will be done at
      the same speed in any direction]

      Pit stops that are 50km apart are a problem for a large infantry
      group proceeding at 25 km/day. In order to drink and refill every
      other day each person will need to carry the extra day's water. That
      will be about 10 kg added to an already heavy load. That would either
      slow the speed per day even more, or require recuperation days at pit
      stops. Adding pack animals is a partial solution, but if you have
      thousands of soldiers you'll need hundreds of animals and every pit
      stop will have to provide a lot more water. And even when the pit
      stops are nearer to each other, what may be an adequate pit stop for
      a caravan may not have enough water for thousands of men. And an army
      can't reach its destination and ask the enemy to wait patiently
      several days for the exhausted soldiers to recuperate ...

      All this should be familiar to ANErs - people and caravans have
      routinely crossed the NE deserts in various paths, but military
      forces had a much more difficult time and were limited in their
      choice of routes. E.g. practically all military expeditions to and
      from Egypt used the "sea route" along the northern part of the Sinai
      because it has a lot of watering pit stops, because the terrain is
      mostly flat, and because the proximity of the sea makes the climate
      more clement. The trade route going through central Sinai is a
      perfectly good route for caravans but is practically impossible for
      large infantry forces.

      With livestock herds the desert crossing strategy, in the rare cases
      when such a crossing must be done, is to force march them between
      several pit stops and make a long recuperating stop at an oasis where
      they have both water and food.

      I hope this made the picture somewhat clearer.



      Ariel.

      [100% bona fide dilettante ... delecto ergo sum!]

      ---
      Ariel L. Szczupak
      AMIS-JLM (Ricercar Ltd.)
      POB 4707, Jerusalem, Israel 91401
      Phone: +972-2-5619660 Fax: +972-2-5634203
      ane.als@...