SCY125 : Politiko Kannouris

Ancient Check Dam

Grid reference: 519440/3874520Cadastral plan:
SIA: SIA 7 (Politiko Kokkinorotsos)
Survey unit: 3164

This POSI is a small check dam constructed of large stones preserved on a ridge about 100 m upstream (southwest) from Politiko Phorades (SCY100). Large (0.3-0.6 m diameter), sub-angular to sub-rounded stone boulders of basalt, diabase and gossan are arranged in nested, stacked courses, approximately 3 m high and 8 m wide (including what are likely collapsed blocks at its perimeter); its preserved length is about 20 m. The uppermost course is two boulders wide. The lower courses are permeated with a fine-grained (sand to silt) matrix.

This structure is clearly of human manufacture. Many of the boulders are exotic to the Kouphos River drainage. Most of the stones reveal little sign of water wear, which is interpreted to indicate that they were not carried by and collected from the Kouphos. Large, sub-angular blocks of gossan came from quarries located several hundred metres to the northwest on or around Politiko Kokkinorotsos. Other sources of these types of stones derive from an even greater distance.

The Kouphos displays a distinct change in geomorphological character at this structure. Overall the Kouphos River has parallel sets of terraces along straight reaches marked by angular bends largely governed by the nature of the underlying basalt bedrock. The floodplain is distinctly wider and higher behind the dam. Immediately upstream from the Kouphos is a set of nested, curvilinear terraces along the cut bank of the channel. Such terraces in this position are unusual; they are only present elsewhere on the inside or slip-off slope of channel bends. SCY125 is on the inside of a slip-off slope of the meandering Kouphos River.

The purpose of the structure is to impede the flow of water in the Kouphos. It is less clear if the intention was to store water (dam) or to trap sediments (check dam). The dam was constructed across the bottom of what was likely to have been the active channel of the Kouphos River at the time. It is oriented at right angles to the fall line of the Kouphos. Exposed on the upstream side of the dam are fine-grained deposits that may represent sediment trapped behind the structure. The fine-grained material within the structure represents constructed infilling or trapped sediments.

The spatial and stratigraphic relationships of the structure with nearby features provides some insight into its purpose. The base elevation of the structure is about 2-2.5 m above the bed of the modern channel, which coincides with the channel elevation at the time the smelting site at SCY100 (Phorades) was in operation. Hence, one possible purpose would have been to store water for the smelting site. However, other evidence and reasoning lead us to conclude that it was a check dam. The use of check dams on this landscape was common in all periods, and SCY125 could be the earliest of its type. Although less likely, a dam construction date of earlier than or contemporary with the smelting at SCY100 cannot be ruled out. Whether or not it was originally designed for water storage, its purpose is essentially that of check dam as it effectively trapped at least 2 m of sediment. Incision migrating up the Kouphos led to the attack on the pillow basalt at the northern end of the dam, where it is relatively easier to erode compared to the massive boulder structure. As the channel migrated to the north it has undercut the ridge topped by SCY123. Pottery and construction stones from this ridge-top site ran down the eroded cut-bank. Thus, the dam cannot be significantly older than the Iron Age structure at SCY123. The prism of alluvial fill behind the dam allows for formation and preservation of the unique terraces of the Kouphos that are present here. The dam itself is now being undercut and eroded away by a down-stream migrating meander of the Kouphos River that is attacking the underlying basalt bedrock.