In Israel, the long, dry summer is followed by a short rainy winter season causing high-flow, high-velocity streams and flooding often occurs. Serving as the divider for the north and south lanes of the Tel-Aviv Freeway, the Ayalon channel was designed to handle the surging waters of the Ayalon River during Tel-Aviv’s winter rainy season.
Since the channel's original design, the city has grown dramatically, adding new buildings, roads, and sidewalks. Areas of open ground have been replaced with concrete, decreasing the amount of ground water recharged, and increasing runoff into the original channel. The increase in runoff was not accounted for in the channel design, and the effects of erosion have taken their toll.
The problem was compounded by the introduction of sewage water and other pollutants into the channel. The corrosive effects of the sewage and pollution augmented the already deteriorating state of the channel, primarily protected with gabions and concrete slabs. The integrity of the freeway may have been in jeopardy if action was not taken to restore the channel and improve its erosion control systems.
Engineers needed a solution that would (1) restore the channel and accommodate anticipated hydraulic flow rates, (2) provide a flexible erosion control system that could adapt to the channel’s unstable subgrades and unique design requirements, and (3) provide a costeffective installation.