Notes


Reservoirs

A-B: Northwest reservoir: water level is fixed by height of barrier at 10.
C-D: East reservoir: water level is fixed by height of outlet at 5.
B-D: southern quadrant: several pools whose levels are determined by heights of their barriers.
B:     barrier/weir at southwest point of ditch controls water level in northwest reservoir

  1. Inlet
  2. End of counterscarp (barely visible at northwest where only low counterscarp is needed)
  3. Counterscarp is higher here where ground level is lower and higher bank is needed.  (Break through banks is modern)
  4. Ground level is lowest here, and counterscarp is highest as required.
  5. Outlet at lowest point of ditch (as is appropriate).
  6. Cropmark of drainage trench from outlet. (downhill towards Stonehenge Bottom)
  7. More of drainage trench cropmark
  8. southern quadrant where several barrier/weirs maintain water level in basins along the south slope
  9. south causeway and culvert
  10. southwest : Ground slopes downward from about this point along south quadrant to the southeast where it levels from that point across the east quadrant

barrier/weirs

These structures are undisturbed ridges of natural chalk, occurring only in the sloping southern quadrant, that were left in place by the original builders of Stonehenge.  They extend fully across the ditch and provide the necessary dams to control the flow of water along the south by creating the several pools and low waterfalls.   The westernmost weir determines the water level in the northwest reservoir.  Other barrier/weirs stand about 3 feet or less above the floor of the moat and determine the depths of the water in the basins of the southern quadrant.  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.


Water Level at the causeway

This view (not to scale) illustrates the layout of the moat at the south including the south causeway and the culvert through the causeway. Water flows from west to east  (left to right) from seg. 18 through culvert and into seg. 17, passes over barrier and into  eastern quadrant reservoir. The views below are photos taken in the 1920s after the ditch had been opened by Col. William Hawley. Photos are of the south causeway as seen from the east  (segment 17) and from west (segment 18) "Stonehenge in its Landscape" English Heritage, 1995, p.87,89)

Source of information used in this design is "Stonehenge in its Landscape", English Heritage, 1995, p.87,89 (below)

"Stonehenge in its Landscape", English Heritage, 1995, p.87

"Stonehenge in its Landscape", English Heritage, 1995, p. 89


South

South unlike …

Page 68

‘The portion of the ditch excavated [i.e. C29, in 1926] was unlike any that had previously been encountered. The frequently occur­ring bays with lateral projections were more emphasised on the south than in any other area, the change appearing to begin at 40ft (12.2m) on the east side of the new causeway and to be continued on the west in more or less marked manner up to where the excavation of this season ended.’ (Hawley 1928,165)

("Stonehenge in its Landscape", English Heritage, 1995, p.68)

The slope of the south quadrant requires the “lateral projections” (barriers), and the south is the only area where the barriers are found. Orion


Scarp

###


Walker also comments on the importance of Col. William Hawley's work.

"Stonehenge in its Landscape", English Heritage, 1995, p.65, K.E.Walker

To consider the excavated length of Ditch as a single phenomenon would clearly have been possible only if a very general approach had been adopted; there is too much information to be easily assimilated. Treatment by excavation trench would have been reasonable but would have ignored the advantage of having such a long stretch of excavated ditch to study. It is rare to have a chance to view a prehistoric monument on such a scale and as much as possible should be made of the oppor­tunity, however flawed the site recording. Because of this the approach adopted here has been to attempt to view and discuss the Ditch in units which may have had some reality at the time the Ditch was constructed. This is clearly an ambitious and possibly presumptive ap­proach, the success of which is perhaps difficult to measure, but it has the merit of using divisions which are only potentially artificial instead of certainly so.
When the plan of the excavated Ditch is viewed as a whole its irregularity is immediately apparent, and this view is strengthened if the ditch profiles are also consid­ered. Lt-Col Hawley noted the irregularity of the Ditch in plan and section and he also drew a distinction between what he termed normal `ditch' and `craters'. The latter were rounded segments demarcated by changes in depth of the Ditch floor, usually including a ridge of chalk between each crater and the next, or between the crater and the ditch. These ridges did not usually reach the level of the stripped chalk surface but could reach a height of several feet (eg the ridge between Segments 16 and 17 is 3fr/0.9m high). Some lengths of Ditch, particularly those around the southern part of the circuit, have a markedly more segmented appearance than others and some at least of the terminals are clearly bounded in this way. It was initially considered that a division following Hawley's into bounded segments and unbounded lengths of Ditch would be a workable method of separating lengths for discussion, reflecting real differences in the way the feature was dug. Once this was attempted, however, it became clear that the lengths of Ditch not designated as craters by Hawley were also irregular and showed signs of having been dug as discrete lengths rather than in a single operation.


Struck Flint

At the north-eastern end of the segment there appears to have been a concentration of antler and animal bone in the primary filling on the bottom. It included an antler pick with part of the skull attached lying directly on the Ditch bottom, with at least three long-bones, four phalanges, and some other fragments. One of the long-bones was tentatively identified as human and two as pig (5/5/192 1). The layer of struck flint was only just present in the most easterly strip of this segment, strip `A', but was present westwards from B', and-the concentration was particularly marked in strips C and D. Here Hawley notes that `they are much trodden into the chalky mud about 1-1/2" to 2" [0.04-0.05m] thick covering the chalk floor of the ditch [1301]. They are so thickly coated with hard mud that it is impossible to see if any are implements until they have been well soaked in water' (25/4/1921). The concentration contin­ued into strip 'E' where Hawley notes that struck flints were found all over the bottom `but chiefly in the centre' (in E4 and E5) (20/4/1921).
("Stonehenge in its Landscape", English Heritage, 1995, p.84)


Opportunistic Knapping

("Stonehenge in its Landscape", English Heritage, 1995, p.68)

The earliest deposit on the Ditch floor was a layer occasionally mentioned by Hawley which he interpreted as foot-trampled mud on the open ditch floor, below the chalk rubble primary fill (eg in Segment 3). According to his description of Segment 3 this deposit was often associated with the `layer' of struck flint which he found in many segments (Table 8: Ditch phase 1). Deposits of chalky mud are not uncommon on the bases of chalk-cut ditches, and appear to be the product of the first winter's weathering (Chapter 1). The association of struck flint with this deposit suggests that the flint could represent opportunistic knapping of flint encountered during the digging of the Ditch. Harding (Chapter 9) suggests from his analysis of the little surviving flint assignable to the Ditch that some nodules are likely to have been encoun­tered during its construction and that some of the cores from phase 1 contexts in the Ditch had been made from `fresh' flint. This is also indicated by the presence of flint nodules in the Counterscarp Bank (Hawley 1923, 14).


Dark Layer

"Stonehenge in its Landscape", English Heritage, 1995, p.81”
A stratum of dark, earthy matter occurred near the bottom varying from In [0.08m] to Bin [0.20m] in thickness, which had the ap­pearance of decayed vegetable matter, possibly with some wood in it, and there was also a good deal of chalky clay compo. The dark matter contained no object [sic], and below it there was sedimentary chalky mud 6in [0.15m] thick, such as is usually found on the bottom but without the flint flakes' (1928, 155) (WA 2591). This may be equivalent to the dark layer found elsewhere in the' Ditch, although here there is no men­tion of the primary chalk rubble and its stratigraphic relationship to it. The more detailed description in the Diary makes clear that the usual layer of flint flakes was entirely absent here, nor were there any recognisable antler picks, though three small points of tines were found (Diary bid). Hawley speculates that the Ditch may have been disturbed but concludes that there was no evidence that the disturbance was recent and he notes that the very organic appearance of the dark layer was unusual in view of its apparent antiquity (ibid). He also makes the general comment, noted only in the Diary, that where there were recognisable barriers between segments they almost always had `a layer of clay over and at the sides of them' (Diary 1925, July-August, A17-Al8).


sediment

http://www.ies.wisc.edu/research/wrm00/educmorph.htm

When a free-flowing river meets an impoundment behind a dam, the river’s flow slows considerably. The river uses the energy of its flow to carry sediment in the water, so as the flow nearly stops in the impoundment, coarse silt and sand and gravel settle on the bottom of the impoundment. Finer silt and clay suspended in the water are carried out into the impoundment and past the dam. Woody debris, such as branches, collects in the impoundment behind the dam. This process results in large amounts of sediment accumulating in the impoundment, and consequently, the river downstream of the dam becomes “starved” for sediment and woody debris. This sediment carries nutrients vital to the food production for the biota of the river, and the woody debris provides habitat for the biota. The amount of sediment that builds up behind a dam depends on the number of years the dam has been in place and the amount of sediment that the river carries into the impoundment during that time. The geology, soils, vegetation, and topography or slope of a watershed are important in determining sedimentation rates. Even more important are land-use practices in the watershed. Agricultural, construction, and other activities and land-use practices can either mitigate or exacerbate sedimentation. Some impoundments store very little sediment because dam operation flushes out accumulations of sediment.


 Social Status of Diggers

("Stonehenge in its Landscape" English Heritage, 1996, p.109)
This is in contrast to, for example, the eastern length of the Ditch, where for most of the length from Segment 2 to Segment 16 the former exist­ence of segments has to be postulated from changes in Ditch plan, combined with changes in the Ditch floor, and Hawley's observations of slight, remnant ridges.

Although the analysis of the Ditch demonstrates beyond reasonable doubt that it was constructed in segments, it is not possible to establish with the same degree of certainty that there was ever a period at which all the segments survived in place with the ridges between them, rather than the ridges between segments being removed progressively as Ditch construction proceeded. Neither is it possible to be certain that the segments were a purely functional means of digging the Ditch. The use of segments in causewayed enclosures, for instance, is generally now considered as being likely to relate to construction by family groups, lineage groups, or other meaningful social divisions. The fact that the segments on either side of the main entrance are fairly clear ones (i.e. Segments 99 and 100, and 1 and 2) hints that they may have been recognised as important in more than purely practical terms. Why else should these have been preserved when most other segments were amalgamated? In the southern part of the Ditch on either side of the southern entrance, the terminals of the Ditch were also left as clearly defined segments (i.e. Segments 17 and 18). This is in contrast to, for example the eastern length of the Ditch, where for most of the length from Segment 2 to Segment 16 the former existence of segments has to be postulated from changes in the Ditch plan, combined with changes in the Ditch floor and Hawley’s observations of slight, remnant ridges. ("Stonehenge in its Landscape" English Heritage, 1996, p.109)


Layer of Clay

("Stonehenge in its Landscape", English Heritage, 1995, p.81)
The dark layer occurs here and appears to have been particularly pronounced and very organic (2590): `A stratum of dark, earthy matter occurred near the bottom varying from 3 in. [0.08m] to 8 in. [0.20m] in thickness, which had the ap­pearance of decayed vegetable matter, possibly with some wood in it, and there was also a good deal of chalky clay compo. The dark matter contained no object [sic], and below it there was sedimentary chalky mud 6 in. [0.15m] thick, such as is usually found on the bottom but without the flint flakes' (1928, 155) (WA 2591). This may be equivalent to the dark layer found elsewhere in the' Ditch, although here there is no men­tion of the primary chalk rubble and its stratigraphic relationship to it. The more detailed description in the Diary makes clear that the usual layer of flint flakes was entirely absent here, nor were there any recognisable antler picks, though three small points of tines were found (Diary bid). Hawley speculates that the Ditch may have been disturbed but concludes that there was no evidence that the disturbance was recent and he notes that the very organic appearance of the dark layer was unusual in view of its apparent antiquity (ibid). He also makes the general comment, noted only in the Diary, that where there were recognisable barriers between segments they almost always had `a layer of clay over and at the sides of them' (Diary 1925, July-August, A17-Al8).


Segment28

The final segment to be excavated by Hawley (part of C29) is the longest in this sector of the Ditch and appears to mark a change in the way the Ditch was originally dug. The floor of this segment was level with the top of the step up from the segment to the east (27) and it continued more or less at that level throughout (profiles 18, 19, and 20). The sides were more or less vertical and the width was c 14ft (4.3m) irt the east, contracting to c 9ft (2.7m) where the excavation ended in the west. It was also very shallow, only c 2ft 7in (0.8m) in depth towards its eastern end and about 18in (0.5m) at the end of the excavation.
Hawley notes that where the Ditch passed out of the excavated area it appeared to be set to continue at the same shallow depth but that probing beyond the end of the excava­tion indicated that within a short (unspecified) distance it was of a more typical depth.
The Ditch underlay the former roadway through the monu­ment, a fact which Hawley took to account for the great hardness of the Ditch filling here. There is little observation of the primary filling in either the Diary or the published report although he does note that `the level chalk bottom looks as if it had been patted down by feet passing over it' and there were `a few flint chips on the bottom', the latter throughout most of the length of the segment (1/7/1926; 1928,164-5).
("Stonehenge in its Landscape", English Heritage, 1995, p.92)


Elevation