* This is to comment on plans being proposed by environmental and recreational interests to convert the existing concrete-lined channels of the Los Angeles River and some of its tributaries to soft-bottom, green-belt streams. The following is intended to give some perspective on the magnitude of structural and hydraulic problems that must be considered in all plans to control or to live with the Los Angeles River.
The elevation of the Los Angeles River at Sepulveda Dam is 700 feet above mean sea level (about 50 river miles upstream from Long Beach). The elevation of Lake Erie is about 570 feet where it empties into the Niagara River, which then flows over a vertical drop of about 160 feet at Niagara Falls in its way to Lake Ontario. To keep the velocity of the Los Angeles River slow enough to prevent erosion of a soft-bottom channel, "drop structures" totaling four times the height of Niagara Falls would need to be built between Sepulveda Dam and Long Beach. Also, flood flows in the Los Angeles River can exceed 200,000 cubic feet per second, which is much greater than normal flow over Niagara Falls.
The construction many years ago of concrete channels to control high-velocity floods in Los Angeles County should not be lamented. The alternatives then were either to construct flood-control improvements, which were economically justified, or to relocate people who were living in flood plains and were in constant danger. The latter was not politically feasible. Removal of existing concrete channels would require acquisition of thousands of acres of developed flood plain areas adjacent to the river and would now cost taxpayers billions of dollars.
At this time, it is obvious that, for safety and practical reasons, the hazard from high velocity floods should still be the primary criterion used in developing all plans to modify or improve the existing channels of the Los Angeles River and its tributaries. On the bright side--with proper planning and design--much land adjacent to the concrete channels can still be used for recreation, rapid transit and/or open space, as long as access is provided to maintain the essential flood-control structures.