Reading a Dry Watercourse in the Limestone of Apokoronas The first two rides in Reading the Landscape began with things that were immediately visible. The salt pans were cut into the coastal rock beside the sea. Stone was everywhere across the limestone country of Apokoronas. Today was different. The subject was something that was no longer there. Water. It was August, and the watercourse was dry. But the absence of water did not mean that there was nothing to see. The ground itself recorded what happens when the water returns. The ride covered 26.1 kilometres with 600 metres of ascent and 600 metres of descent. Moving time was 1 hour 33 minutes, with an average moving speed of 16.7 km/h and a maximum speed of 54.4 km/h. The highest point was approximately 310 metres, with the lowest at around 20 metres. This was another ride through familiar country, but once again the purpose of Reading the Landscape was to stop and examine something that I would normally ride past. The Dry Watercourse At first sight there is little remarkable about it. A narrow channel descends through the trees. Limestone is exposed across much of its bed. Stones and smaller fragments lie in the lower sections. Vegetation crowds the sides and, in places, extends towards the channel itself. There is no flowing water. Yet almost everything about the feature has been influenced by water. The channel provides a natural route down the slope. When sufficient rain falls, water from the surrounding ground is concentrated into it. What is dry for much of the year can then become part of the drainage system carrying water downhill. The photograph was taken in summer, when the contrast is particularly pronounced. The soil is dry. Much of the surrounding vegetation is adapted to the long Mediterranean summer. The exposed limestone appears almost completely disconnected from the winter rains. But the shape of the ground tells a different story. Water That Comes and Goes One of the defining characteristics of the Cretan landscape is seasonality. Rainfall is concentrated principally in the cooler months, while summers are characteristically hot and dry. A channel that contains no water in August may therefore look very different during or immediately after sustained winter rainfall. That distinction is important. A dry watercourse is not necessarily an abandoned watercourse. It may simply be between periods of flow. The amount of water passing through it will depend upon rainfall intensity and duration, the size and character of the catchment above it, the permeability of the surrounding ground and the condition of the soil when the rain falls. A short shower may produce little visible response. Prolonged or intense rainfall can be quite different. Once the capacity of the surrounding ground to absorb water is exceeded, surface runoff increases. Water begins to follow the easiest available routes downhill. Small flows combine. Existing depressions concentrate them further. The landscape begins to drain. Limestone and Water Part 2 of Reading the Landscape examined the limestone that underlies so much of Apokoronas. Water is one of the principal agents acting upon that limestone. The relationship is complicated because water does not simply travel across the surface. Limestone is commonly fractured by joints and fissures. Rainwater can enter these openings and, because slightly acidic water slowly dissolves calcium carbonate, the fractures can gradually become enlarged. This is fundamental to the development of karst terrain. Some water therefore moves across the landscape as surface runoff, while some enters the limestone and travels underground. The balance between the two is not constant. During light rainfall, a considerable proportion of the water may infiltrate the ground. During intense rainfall, particularly where exposed bedrock, compacted soil or steep slopes restrict infiltration, surface runoff can increase rapidly. The dry channel photographed on today's ride belongs to that wider system. It is one of the places where the shape of the ground concentrates water when conditions allow it. Reading the Channel The evidence lies beneath the wheels. The bed is irregular. In places the limestone itself forms the floor of the channel. Elsewhere there are accumulations of smaller stones, fragments of rock and soil. These materials do not all behave in the same way when water passes through. Fine material can be carried relatively easily. Larger fragments require stronger flows before they move. Exposed bedrock remains in place but can influence the direction and velocity of the water passing over it. The result is a constantly changing relationship between erosion, transport and deposition. Water removes material from one place and deposits it somewhere else. On a steep section, flow may have sufficient energy to scour soil and loose stone from the channel. Where the gradient decreases, or where an obstruction reduces the speed of the water, some of that material may be deposited. Over repeated periods of runoff, the channel is modified. Not dramatically during every storm, and not necessarily in a way that is immediately obvious. But incrementally. The dry channel seen in August is therefore the temporary condition of a feature shaped during wetter periods. Vegetation and the Watercourse The vegetation provides another clue. Trees and shrubs grow close to the channel and along its sides. Their presence is influenced by several factors, including soil depth, shade, competition and access to moisture. The channel itself can create small variations in all of these. Soil and organic material can accumulate in protected places. Fractures in the limestone provide routes for roots. Shaded sections lose moisture more slowly than exposed ground. Roots, in turn, influence the channel. They bind soil in some places and penetrate fractures in others. Fallen branches and accumulated vegetation can obstruct runoff temporarily, trapping stones and finer material behind them. A later period of stronger flow may rearrange everything again. Water, stone, soil and vegetation are therefore not separate parts of the landscape. They interact. A Mediterranean Landscape In northern Europe, the presence of a watercourse is often associated with visible water. Crete requires a slightly different way of looking at the ground. Here, some of the most obvious evidence of water can be found where there is none. Dry stream beds, gullies and drainage channels cross a landscape that may remain without significant rainfall for months. Their importance becomes apparent when the weather changes. The first substantial rains after summer encounter ground that has been exposed to heat and prolonged dryness. Dust, loose soil, leaves, twigs and stones have accumulated. Channels that have appeared inactive begin carrying water again. The transformation can be rapid. Tracks can become drainage routes. Depressions fill. Water follows wheel ruts and existing erosion channels. Loose material begins to move downhill. For anyone travelling through the countryside, this seasonal change affects movement as well as appearance. Water Beneath the Wheels For a mountain biker, water leaves evidence everywhere. A rut across a track may have begun with tyres, but subsequent rainfall can enlarge it. Loose stone on a descent may have been moved by water. A section of exposed bedrock may exist because the soil that once covered it has been washed away. Material accumulated at the bottom of a slope may have travelled there during repeated periods of runoff. The condition of a familiar track can therefore change considerably between seasons. A line that is straightforward during summer may be deeply eroded after winter. Loose stones may have moved. Soil may have disappeared. New channels may have formed across the riding line. Sometimes the process is obvious. At other times it is easy simply to describe a track as rough without asking why it has become rough. The answer is often water. From the Mountains to the Sea The significance of these small drainage features becomes clearer when they are considered as part of the larger landscape. Water falling on the hills of Apokoronas does not remain where it lands. Some evaporates. Some is taken up by vegetation. Some infiltrates the soil and fractured limestone. Some travels underground. Some becomes surface runoff. Gravity takes care of the direction. Downhill. Small drainage lines feed larger ones. Water enters streams and rivers or disappears underground before emerging elsewhere. Eventually much of it reaches the coastal plain and the sea. The individual dry channel beside today's route is therefore only a small part of a much larger movement of water through the landscape. Its scale is modest. The process is not. Reading What Is Absent This was the third encounter in Reading the Landscape, and perhaps the first in which the subject had to be reconstructed from what it had left behind. There was no stream to photograph. No cascade. No pool. Just a dry channel descending through limestone and vegetation. But the water had left evidence. The shape of the channel, the exposed rock, the loose material in its bed and the arrangement of the surrounding ground all record the movement of water during wetter periods. Once that is recognised, a dry watercourse stops being an empty feature. It becomes evidence of a process. The salt pans in Part 1 showed the relationship between people, rock and the sea. Stone in Part 2 examined the limestone beneath much of Apokoronas. Today, water connected those subjects. It acts upon the stone, follows the shape of the land, disappears into the limestone, reappears elsewhere, moves material and alters the tracks across which I ride. In August, much of that process is hidden. But the evidence remains. You only have to stop and read it. Reading the Landscape is 50 Rides, 50 Encounters Part 1 — The Salt Pans Part 2 — Stone Part 3 — Water The next encounter will come from the next ride.