GRAVEL DISPLACEMENT AFTER WINTER RAIN ON UPPER BENDS IN CATALKOY

Location: Çatalköy

Upper Catalkoy connects hillside residential roads to the main coastal corridor through a sequence of moderate bends. During winter rainfall, these bends experience a specific environmental shift that does not resemble landslide activity or major debris flow.

The exposure develops from minor surface displacement.

Rainwater descending from higher elevations carries fine gravel, small stone fragments and loose shoulder material toward the inside edges of curves. The volume is limited. The visibility is subtle. The effect concentrates precisely where steering input is already active.

After sustained winter rain, particularly within 24 to 72 hours of heavy precipitation, small clusters of gravel accumulate near the inner arc of upper bends.

Drivers rarely expect this.

A typical scenario unfolds on a downhill approach toward the lower Catalkoy corridor. A vehicle enters a gentle bend at normal residential speed. The driver maintains steady steering and light throttle or minimal braking.

Mid-curve, the tires encounter a thin layer of displaced gravel.

The response is not dramatic loss of control. It is reduced lateral grip for a fraction of a second. Steering correction becomes slightly sharper. The vehicle tracks wider than anticipated.

If an opposing vehicle is present, lateral spacing narrows briefly. If the curve transitions into a straight segment with immediate braking requirement, stopping precision becomes marginally less stable.

The exposure window peaks shortly after rainfall subsides rather than during active rain. While rain continues, water movement may keep gravel dispersed. Once precipitation stops and surface water drains, loose material remains.

Upper Catalkoy bends are not steep alpine curves. They are moderate arcs embedded in residential terrain. Their familiarity can create overconfidence.

Drivers accustomed to consistent asphalt friction may not anticipate micro-variability following rainfall.

Another pattern emerges when vehicles travel uphill through the same bends. Acceleration over displaced gravel produces minor wheel spin in certain vehicles, particularly those with lighter rear axle load.

Between December and February, this environmental behaviour repeats several times depending on rainfall frequency.

Importantly, this is not a road design failure. It is a natural byproduct of hillside drainage interacting with paved surface.

Maintenance crews may clear larger accumulations, yet fine particles often remain undetected because they do not obstruct the lane visually.

The highest sensitivity occurs in the first few passes after rainfall. Subsequent vehicle movement redistributes gravel gradually, reducing concentration.

Even so, for a limited period, the friction profile of upper Catalkoy bends differs from dry-season norms.

The curve does not tighten.

The surface changes.

Drivers approaching these bends during winter should anticipate slightly reduced lateral stability immediately after rain events.

The environment corrects itself over time.

But during the short post-rain interval, micro-displacement on upper Catalkoy curves narrows reaction margin.

The geometry remains constant.

The texture does not.