Many ancient sites were situated close to the rivers, and had to be protected against flooding. As we know now, pistiros was situated on a very low hill, only some 2 m above the surrounding terrain, perhaps some 2 m more above the normal height of the river in summer. The quaternary geologists confirmed that the surroundings of the small hill were rather marshy at the time of the existence of the emporion. This was good for the protection from enemies, but the floods caused problems every year. We found traces of at least seven big floods in the city while in existence and also further evidence that behind its walls there was a marshy area for most of the year. One of the main goals of pistiros’ town planning from its beginnings was to protect the city from mud and water.
The problem of letting the water from heavy rains dissipate as quickly as possible was the reason why a sophisticated canal system was built together with the city wall during the third quarter of the 5th century bc. The main canal in the preserved part of the city ran roughly in the middle of the main east-west street, but to avoid flooding the eastern gate, just before entering its area it bifurcated, one branch running northwards and a second southwards. The main canal was carefully repaired after two or three destructions of the emporion, while raising the level of the bottom of the canal together with the paving of the main street. The original bottom was hardened in a way similar to macadamasing it. The last city, reconstructed around 300 bc, built a new small canal leading from the inner gate of the eastern gate, and additional small drains in other places, as the old canal apparently did not work properly.
The southern outlet across the city wall is the best preserved. It was closed by a kind of fence preventing the enemy from entering the city secretly through the canal. The lead fixing the metal fence to the stones of the tunnel is preserved. The best parallels to this device we know are constructed across the city wall of amphipolis, another city founded during the second half of the 5th century.
The main canals were – as far as can be found and supposed – by stone slabs, of which some remained in situ under the main street, but most of them were taken away in roman times or later as good building material The main canals were – as far as can be found and supposed – covered by stone slabs, of which some remained in situ under the main street, but most of them were taken away in roman times or later as good building material for secondary use. The drafted margins in the stones bordering the canal are present in all places, but are only several centimetres deep, so perhaps the cover may also have been of wooden planks. Smaller drains were found, in better or worse preservation, in and around the two main houses along the main east-west street. They were made partly of stone, partly of reused tiles.
For drinking water many wells were constructed in all known parts of the city, either for individual oikoi or also for public use. The bottoms of the wells are ca. 4 m below the present surface, and the walls of one of the wells were reinforced by reused pithoi to prevent the soft sand collapsing into it. Our understanding of the system of canals at pistiros shows that the arrangements were little inferior to the level reached by the romans. It documents a high level of town planning even at the margins of the greek world already in the classical period.
