This article is dedicated to the memory of Professor Gerald S. Hawkins who freely provided help in the form of information, suggestions, advice and encouragement, over the years, in the development of this hypothesis.

The authors of "Stonehenge in its Landscape" English Heritage, 1995 express the hope that their publication may:

"… provide the necessary firm foundation on which to build future theories and to construct new research designs, for as with any archaeological site, the project has raised questions which will require an answer in the future.”
("Stonehenge in its Landscape", English Heritage, 1995, p.492)

Below is such a theory:

Plate coloured to show proposed line of feed trench and moat.

The Surrounding Moat
of Stonehenge I

This hypothesis differs from others in that it views Stonehenge as being surrounded by a water-filled moat rather than by a dry quarry-ditch as is commonly believed to be the case. The realization that the Ditch of Stonehenge I may have been a reservoir grew out of research into a larger hypothesis concerning the transport of the stones, one requirement of which is that a large supply of water needed to be available at the level of Stonehenge. It is one of many conditions required by the hypothesis that are confirmed by the records of various archaeological excavations in and around Stonehenge. However, a model of Stonehenge surrounded by a water filled moat (as opposed to a dry quarry/ditch) is noteworthy for its own sake, since it contrasts substantially with any view of the monument previously proposed.

If, as claimed by many writers, the surrounding ditch of Stonehenge I were nothing more than a dry quarry ditch, many of its features have gone without reasonable and coordinated explanation. There has not been a single unified theory that has explained many of the conditions known to exist in the ditch. Only when viewed as a major and important part of the original monument of Stonehenge I do the various pieces of the puzzle fit together to form a single and coordinated view of the surrounding ditch/moat.

Until now, it has been supposed that the ditch surrounding Stonehenge I was nothing more than a dry, ugly, quarry/ditch whose sole purpose was to supply material for the building of the surrounding bank. Writers too numerous to mention have claimed that it is only the bank that was important and that the ditch was merely the inevitable by-product of the building of the bank.

R.J.C.Atkinson “Stonehenge”, 1965, p.23 writes:

“Irregular ditches of this kind, like the outline of a string of very badly made sausages, are characteristic of neolithic earthworks in southern England. Their apparently unfinished state does not mean that the work was abandoned before it was completed, but that the builders regarded the ditch merely as a quarry for material to build the bank. It was the bank which was the important element of the earthwork, and the ditch had no meaning, in itself as a structural or symbolic feature.”

However, there is considerable evidence that the surrounding ditch ranked at least equally with the bank in its importance to the structure of Stonehenge I.


Thanks to the discoveries of Col. William Hawley during his excavations of the 1920s in combination with other known conditions at Stonehenge, it can be said with some measure of certainty that the surrounding ditch of Stonehenge was originally a moat, filled with water that flowed from an inlet at the northwest to an outlet at the east, and which, except for the causeway at the northeast, encompassed the entire site of Stonehenge I.

The surrounding moat of Stonehenge comprises three distinct parts:

  1. The northwest reservoir occupies the north and west quadrants of the ditch. It extends from the northeast causeway to the southwest point of the ditch – about 180 degrees of the periphery. It includes the northwest inlet where water flows into the moat (possibly from an elevated aqueduct) and flows southward. The water level of the northwest reservoir is maintained by a barrier/weir across the moat at the southwest over which the water flows into the south quadrant.

  2. The south quadrant comprises several basins through which the water flows filling each basin to the level of a barrier/weir over which it flows into the next and lower basin to its east.

    A twelve feet wide causeway cuts across the moat at the south. A culvert through the causeway allows the water to flow from west to east through the causeway. The culvert is below the surface of the water and keeps the water level equal on both sides of the causeway. The water level at the causeway is maintained by a barrier/weir some distance (about 40 feet) to the east of the causeway. The water overflows the barrier into the east quadrant.

  3. The east quadrant is on relatively level ground and forms a single reservoir extending from the southeast point of the moat to the eastern side of the northeast causeway. The east quadrant of the moat includes the outlet through which the water flows from the moat and is directed into Stonehenge Bottom via a trench stretching eastward from Stonehenge.

    The northern and southern quadrants are on sloping ground requiring the barrier/weirs at the south to provide the several pools along that quadrant and requiring embankments (dikes) on both sides of the moat at the north. The water level at the west, south and east is below the ground level at those locations, but the water level at the north, because of the sloping ground, is higher than the ground level and so dikes are required to contain the water there. The bank that surrounds the site just inside the moat provides the required dike on the inner side of the moat. There is also an outer bank at the north (a counterscarp) that provides the required dike on the outer side of the moat. This north counterscarp is the only real counterscarp at Stonehenge; the low bank outside the other three quarters of the ditch/moat is insignificant compared with this major feature at the north. Obviously, due to the slope of the land, the north is the only area where such a bank is required of a moat.

    The writers of "Stonehenge in its Landscape" refer to the irregularity of the ditch at the south. It is noted that the ditch is more segmented at the south and that the depth of the floor of the ditch changes from one segment to the next and that barriers separate the segments when there is a change in the floor levels. Actually these changes in the elevation of the ditch floor are not surprising, since the surface slopes, and the elevation of the surface changes correspondingly. Strategically placed barrier/weirs maintain the water levels of the various basins along the southern quadrant. When the purpose of the ditch as a moat is taken into account, it is to be expected that the sloping southern quadrant will be divided into distinct segments. It is not surprising then that Col. William Hawley found barriers of chalk separating the segments.

No barrier/weirs are required in the other three quarters of the moat, and none have been discovered there. The north and west quadrants have not been excavated, and so it has not been determined whether any barriers exist there. At some time in the future, non-invasive means may be developed and applied to determine the conditions of the moat at the north and west. If this moat hypothesis is correct it is unlikely that any barriers will be found there, since none are required.
The irregularity of the ditch pointed out by K.E.Walker in "Stonehenge in its Landscape", p.65, is particularly pertinent to this discussion, since conditions are just as expected of a moat on that landscape. Walker also comments on the importance of Col. William Hawley's work.

There is no counterscarp required at the west, south and east and there is none such as the counterscarp at the north. There is, however, a low outer bank composed of material (sod, soil and turf) removed from the site of the moat prior to digging out of the chalk and the building of the bank, presumedly so the bank would be built of only clean chalk from the lower levels of the ditch, but the counterscarp at the north is more substantial than the low outer bank and is composed of the same clean chalk as is the inner bank. There is no doubt that the counterscarp at the north represents a major effort of labor and was important to the monument

R.J.C.Atkinson, "Stonehenge", 1990, p.25, writes:

Besides the main bank on the inner side, there are slight but indubitable traces of an outer, or counterscarp, bank as well, which can best be seen immediately north (that is, anti-clockwise) from the entrance to the earthwork. Curiously enough, this feature has seldom previously been recorded, and has otherwise passed unnoticed, although it must once have been substantial, with a width of perhaps 8 ft and a height of 30 in., since excavation has shown that here, as under the main bank, the surface of the natural chalk has been protected from weathering.

The Flint Layer

Since the bedrock underlying the site is quite permeable, it was necessary to provide sealant to the bottom of the moat. A sealant composed of a mixture of clay and chalk with considerable quantities of struck flint added has been applied to the bottom and into crevices on the bottom. Col. William Hawley refers often to a “flint layer”, and to a layer of “purposely applied foot trampled clayey mud” (compo) filling crevices and covering the bottom of the ditch directly atop the natural chalk bottom of the ditch. This durable material, compo mixed with flint, is taken (here) to represent an effective means of sealing the bottom of the moat, much the same as clay is applied today to the bottoms of canals and reservoirs in the area around Stonehenge.

Col. William Hawley refers often to a ‘ubiquitous layer’ of ‘foot trampled clayey mud’ with ‘much struck flint’ mixed in and ‘purposely applied’. It is known as the “flint layer”. There is no doubt that the bottom of the moat was deliberately lined with the artificial, concrete-like material (compo) and that it provided a seal to the bottom of the moat against water seepage, whether or not that was the reason for it. Whatever the intended purpose of the flint layer, it may not be argued that permeability of the underlying rock precludes the possibility of a moat.

The matter of “compo”, “flint”, “reservoirs”, and “sealant” is not without modern parallel. Here is a link to Arthur Becket’s, about dewponds that bear remarkable similarities to the Stonehenge moat. It seems that many “dewponds” exist on the chalk plains of southern England. These are artificially made ponds most of which are situated at the tops of hills and have no streams or springs feeding into them, yet they manage to stay filled with water, even after ponds at lower elevations go dry. The dewponds run dry only when their sealants fail or during most severe draughts.

The ponds often serve to provide the water requirements for several hundred head of sheep and cattle. The linings of the bottoms of these dewponds are identical in many respects to the linings of the Stonehenge moat. The linings are composed of puddled compo containing much flint and are applied in layers directly on the chalk floor of the pond. The mix of compo and flint is used to fill any cracks or crevices in the floors of the ponds just as it is in the floor of the moat. The compo and flint is quite effective in preventing leakage from the ponds. It is made quite clear in Becket’s article that flint is an important ingredient of the sealant, just as Col. William Hawley emphasized the flint layer at the bottom of the moat. While some of the ponds are known to be modern (nineteenth century), some are believed to have neolithic origin (that view is unconfirmed, however).

More About Dewponds: (Link 1) (Link 2) (Link 3)

The authors of "Stonehenge in its Landscape", English Heritage, 1995, p.68 suggest that the flint layer may represent scraps left over from the “opportunistic knapping” of flint discovered in the process of the digging of the ditch. There is some argument against the flint layer having been the result of opportunistic knapping, however.

The Dark Layer

As occurs on the bottoms of bodies of water (ponds, rivers, canals and moats etc.) there is resting directly on the bottom of the moat a dark layer of decayed organic matter. Col. William Hawley reports this ‘ubiquitous dark layer’ throughout his excavations of the ditch. At some places the dark layer was as thick as 8 inches and rested directly on the bottom or, as usual, directly on top of a ‘purposely applied’ layer of compacted trampled clayey mud (compo) that covers the bottom. This dark layer resting on top of the layer of compo and below the primary fill is interpreted to be the natural deposit of organic sediment that invariably accumulates at the bottoms of such bodies of water.
Col. Hawley refers to the "very organic" nature of the dark layer and the possibility of "wood in it". This compares with the kind of sediment that accumulates on the bottoms of impoundments behind weirs.

Deep Craters

The deep craters at the terminals of the ditch to either side of the northeast causeway have given rise to speculation by some writers. It is suggested by the authors of "Stonehenge in its Landscape", English Heritage, 1995, p.109 that the reason for the craters being different from the rest of the ditch may relate to the social status of the diggers. Another possibility may be:, since the ditch is the source of the chalk for the bank, and since more material would be required at the ends of the bank if it were to wrap around the ends so as to enclose the ends of the ditch within the bank, that the deeper craters at the ends of the ditch could be accounted for by the requirement of a larger amount of material there. How else could the material for the extra length of bank be obtained than to go deeper? Apparently the bank did indeed originally wrap around the ends of the ditch and was at a later time deliberately redeposited back into the ditch. Col. William Hawley reports finding deliberately redeposited chalk near the ends of the ditch on both sides of the northeast causeway.

Clay on Barriers

The most efficient method of providing the required weirs in the southern quadrant was to simply leave the natural material undisturbed wherever the weirs were needed. Since the natural material is chalk and, since the chalk is subject to rather rapid erosion by the flow of water, the weirs are protected by a layer of clay on the tops and sides of them. The soft chalk would have been eroded rapidly by the water passing over it, whereas a layer of clay would have withstood the effects of the water and indeed the clay has endured and was evident to Col. William Hawley in the 1920s.

Southwest Barrier

The barrier at the southwest point of the moat determines the water level in the northwest reservoir. At the end of his digging, Col. William Hawley reports a condition unlike any he had encountered up to that point. Segment 28, the final segment of Col. William Hawley’s excavations was found to be much shallower than any others. It is at the southwest point of the moat beyond which the ground surface levels off and the northwest reservoir begins. At the point where Hawley ended his work the ditch was a mere 18” below surface, but by probing, Hawley discovered that shortly the ditch returned to the normal depth. Hawley reports the filling of the ditch to be of “great hardness” and that the “The level chalk bottom looks as if it had been patted down by feet passing over it.” – a condition Hawley reports finding throughout his excavations of the ditch – and there were “… a few flint chips on the bottom”.

This final segment, #28, of Col. William Hawley’s excavations is interpreted as the barrier/weir at the southwest that maintains the water level in the northwest reservoir. It would have provided a water level in the reservoir somewhat less than 18” below ground level. The water would have overflowed the western end of the barrier and flowed down the sloping surface and into the basin of segment 27, somewhat lower than segment 28. In modern times the shallow depth of the ditch at segment 28 probably led to its becoming a thoroughfare and possibly to the great hardness of the surface, or possibly the surface may have been deliberately made hard by the builders to prevent erosion by the flow of water over it. In any case it would seem that the 'foot patted' bottom of the ditch was deliberately conditioned to withstand erosion.

Eastern Quadrant

There are no barriers in the eastern quadrant. Since the eastern section of the moat lies on level ground, no barrier/weirs are required there and so none are expected. The eastern reservoir includes the lowest point on the periphery of the monument and so an outlet from the moat is required there. There is an outward opening of the ditch at the lowest point to allow for the flow of water from the ditch. From the exact point where the outlet needs to be and evidenced by obvious cropmarkings a, now filled in, trench leads off from the edge of the moat and runs downward toward Stonehenge Bottom.

The Inlet

As mentioned above, water would have been fed into the moat at the northwest inlet, possibly from an elevated aqueduct. This ditch/moat theory is a part of a larger theory that requires the moat, or at least some body of water at the elevation and location of Stonehenge. The moat has become apparent as the result of research into that larger theory. For now, we may say that there is, externally, compelling reason to believe that the water was fed into the moat from an elevated aqueduct. There is also within the moat some indication that the water entered the moat from some height, as from a waterfall.

When water falls, as with all falling matter, of course, it develops some momentum the velocity of which, due to the acceleration of gravity, depends on the distance it falls. The water falling into the reservoir will create turbulence and will stir up any small or light particles on the bottom of the reservoir and carry them away with the current. They will be carried away in the direction of the flow, as will other particles that happen to be on the bottom as the turbulent waters pass over them. The washing away of the small and light particles will create a depression (plunge pool) on the bottom of the reservoir, and the depression will be elongated in the direction of the flow. The size of the depression will depend on the height from which the water falls, the depth of the water in the plunge pool, the rate of flow, the nature of the rock, etc. The larger and heavier chunks will remain and will occupy less space than was occupied by both the large and the small particles. This is all very obvious and no one should have a problem with it. It is just that it is important to the idea of an elevated aqueduct feeding water into the moat. It is the kind of evidence that should be expected of such a system. Amazingly, even after fifty centuries, there is clear evidence at the inlet of exactly the shape of depression to be expected if water had fed into the moat from some height.

In his book “Beyond Stonehenge”, 1973, Gerald S. Hawkins published the elevations at Stonehenge at one-foot intervals. The map of elevation contours has proven invaluable to the development of this theory and especially in verifying the expected elongated depression at the inlet. The map also indicates the subtle differences in elevations that verify the need for diking at the north and for barriers at the south.

Where from here?

Certainly this hypothesis does not answer all of the questions that need to be answered, such as the source of the water and how much water would be needed to keep the moat full considering the permeability of the underlying chalk rock, etc. Also, it remains to be established whether some of the features that are interpreted as necessary parts of a moat are in fact what they appear to be, for example the feature taken to be a culvert through the south causeway. It needs to be determined if the hole in the wall of south causeway actually extends through the causeway to segment 17. Ground radar should be able to resolve that question.

Further testing (core drilling) could be undertaken to determine if there is molluscan evidence of water having been present in the moat.

Noninvasive probing (ground radar for instance) could establish whether or not barriers were left in the unexcavated western & northern quadrants of the ditch (the hypothesis predicts there will be none there, since none are required there by the proposed moat). Barrier/weirs are required only in the southern quadrant by the hypothesised moat, so to show that any exist in the north or west could cast doubt on their purpose, and to show they are absent in those quadrants would strengthen the argument that they were for the purpose proposed here.

Ground radar or other noninvasive means could show if there is evidence that water has been fed into the hypothesised inlet at the northwest. If the moat has ever been filled with water, the water must have been fed into it at precisely its highest point, i.e. the northwest where (coincidentally) there is an outward opening through the bank. Ground radar or other noninvasive means could detect any trenches or other means of directing water from the watershed into the moat. Ground radar could also show whether or not a trench for the purpose of carrying water away from the moat and into Stonehenge Bottom has ever existed. The exact point where such a trench would originate is at the precise lowest point on the moat where (coincidentally) there is an opening through the outer bank, just as at the northwest inlet.

Segment 28 at the southwest point in the ditch, that was never deeper than 18” below grade, is precisely where a dam is needed to contain water in the northwest reservoir. Col. William Hawley, whose excavations ended with segment 28, determined by probing that the ditch just west of segment 28 returned to normal depth. If segment 28 were indeed what is proposed here (a dam), then core drilling immediately to the west of that segment should yield considerable organic sediment at the bottom of the ditch. Such a deposit of organic sediment would be the result of water having been impounded in the northwest reservoir and having overflowed the dam and into the southern quadrant. It is predicted by the hypothesis that there will be a considerable, thick deposit of organic matter on the bottom of the ditch just west of segment 28.

Thanks go to English Heritage, Gerald S. Hawkins,
R.J.C.Atkinson, Col. William Hawley, Christopher Chippindale,
and the many researchers and writers of Stonehenge
without whose work this hypothesis would not have been possible.

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To be continued

(c) Orion J Beadling 2003.