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State comptroller warned about Ayalon flooding
By SHARON UDASIN
10/01/2013
Plan to safeguard TA area’s main highway went through series of committees,subcommittees and steering committees.
 
While a State Comptroller’s Report from nearly a decade ago warned that the Ayalon River canal must be diverted to avert an eventual overflow, the relevant government authorities did not act quickly enough to prevent the deluge that crippled Tel Aviv’s main traffic artery on Tuesday.

A chapter of the December 2004 State Comptroller Audit Report on Local Government, titled “Treatment of Drainage Infrastructure,” took a look at the management – and mismanagement – of drainage facilities all over the country, where drainage pipes, canals and rivers funnel rainwater and runoff into the sea.

Because prevention of flooding is entirely dependent on the relationship between the capacity of the drainage system and the expected water flow, it is crucial to keep drainage infrastructure a top priority, the report said. A lack of investment in drainage facilities is likely to result in much greater future costs, the state comptroller wrote.

Following severe flooding that occurred in the winter of 1991-1992, the State Comptroller’s Office conducted an audit in 1993, which revealed many deficiencies in these areas, and the office once again reassessed these issues for the months of July to December 2003.

One issue that the State Comptroller’s Office dissected in particularly was the drainage situation of the “Netivei Ayalon” (Ayalon Highways) project. While traversing the Ayalon riverbed with a highway and railway, it became necessary to built a concrete canal to channel the river’s floodwaters in the 1970s – a canal that would be under the auspices of the Yarkon River Drainage Authority, the report said.

While the flow capacity of the canal – both in 2003 and today – allows for floodwaters barreling through at up to 400 cubic meters per second, professionals have long agreed that according to the accepted standard for major drainage routes, the canal must be able to tolerate a flow of 600 cubic meters per second, according to the report.

“In this situation widespread urban areas are exposed along the Ayalon canal to flooding and to severe damage in a recurrence interval of 15 years or less,” the State Comptroller’s Office wrote.

Over the course of many years, professionals came to the conclusion that it was impossible to expand the canal or to increase its design flow, so one of two options must taken – regulate the flow from upstream or partially divert the Ayalon canal using tunnels to the west, into the sea, the report explained. Because choosing an Ayalon canal solution stretches beyond a single local authority, the plans were delayed for many years, the state comptroller said.

Only due to transportation demand, such as the desire to eventually add a fourth railway track, did the authorities begin to move the solution forward.

In 2002, a private planning company conducted an examination that reconsidered the westward diversion, a choice that the Transportation Ministry and the Yarkon River Drainage Authority supported after the review. In May 2003, the Drainage Authority plenary approved the partial rerouting of the Ayalon River, but the cost was expected to be very high – between NIS 800 million and NIS 1 billion, the report explained.

Afterward, the plan went through series of committees, subcommittees and steering committees, which analyzed its costs and benefits.

By early 2004, the Tel Aviv District Committee for Planning and Building generated an alternative plan, as part of the overall master plan for the future Ariel Sharon Park.

Within the park, a buffer reservoir could serve to adjust the upstream flow of the Ayalon River and reduce its flow downstream – significantly reducing costs associated with a tunnel diversion system, the committee argued.

The Ariel Sharon Park reservoir is the plan that is slated to move forward today.

The State Comptroller’s Report from 2004, however, lamented the fact that for a decade no plan for the canal had been advanced, and instead, during that period, the volume of upstream construction grew – increasing the risk of flooding built-up areas.

“The State Comptroller's Office believes that it is not necessary to see drainage regulations and flooding prevention for built-up areas and high-speed roads as issues secondary to transportation or the establishment of a recreational park,” the report said.

In response to a query from The Jerusalem Post, the Yarkon Drainage Authority said that the drainage reservoir plan for Ariel Sharon Park was prepared by a joint Israeli and international team that included the Tahal development group, the Palgey Maim company, the American firm MWH and architects Prof.

Peter Latz from Germany and Alisa Braudo from Israel. The program is based on a master plan for drainage drafted in 2005 and includes a buffer pool for runoff and floodwaters, the authority said.

“The program was designed to curb the tide of the Ayalon River and its tributaries, in order to protect Gush Dan from floods and to adhere to the demand for a 600 cubic meters per second flow,” the authority said. “In addition, this program is an essential condition for building a fourth railway line on the Ayalon, as promoted by the Transportation Ministry.”
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