Regardless of how El Nino shapes up--whether Los Angeles has a 100-year flood or not-- city and county fire departments are gearing up as usual for swift-water rescues. Throughout the year, each department’s swift-water team undergoes training for rescuing victims from the county’s waterways. An average of 6 drownings a year occur in the county’s more than 600 miles of flood-control channels.
The river officially begins in Canoga Park. As it travels southeast, several creeks flow from the mountains through channels into the river, down to the Valley’s lowest point, the Sepulveda Dam. Located about seven miles downstream from the start of the river, the dam catches any water that hasn’t soaked into the ground from a 152-square-mile area. And when it rains heavily, the Sepulveda Flood Control Basin does what it was designed to do--it floods, keeping runoff water from flooding freeways and populated areas.
When the river was all natural, it flooded many times. After a devastating flood in 1938, the U.S. Army Corps of Engineers lined the river with concrete and built Sepulveda Dam. Now only about nine miles of river are unpaved. Some stretches overgrown with vegetation are being cleared by the Department of Public Works and U.S. Army Corps of Engineers, in preparation for a heavy rainy season.
Because of the area’s topography, water moves quickly down the steep mountains that surround the Valley, filling the river and its diversion channels. When that happens and someone falls in a channel, the city and county fire department swift-water rescue teams respond.
Los Angeles River
When flowing, the L.A. River’s water is mostly runoff from mountains and springs. The river isn’t meant for recreation--it’s a concrete channel designed to move water out of the Valley and down to the ocean.
It’s All Downhill
The Los Angeles River drops about 800 feet in just over 50 miles--a slope much greater than the Mississippi River, which descends 1,600 feet over its 2,300-mile course.
Angle of channel walls varies from 30 degrees to 90 degrees. Low-head dams are vertical walls along stretches where there is a drop in elevation. These are especially dangerous because of the “hydraulic” effect caused when the current reverses and recirculates over the same area. Firefighters call low-head dams “death traps” or “drowning machines” because it is nearly impossible for a victim to escape.
For most of its 52 miles, the Los Angeles River is a concrete channel with sloped walls, which are difficult for rescue victims to hold onto. A few sections of river are natural bottom. The width of the river averages 30 feet to 60 feet; it is 500 feet wide--its maximum--at its mouth at Long Beach.
Mapping the L.A. River
The Los Angeles City Fire Department uses detailed maps of the Los Angeles River to locate strainers and dams as well as good access points for rescues. The map is drawn in segments, showing how fast water will be moving during peak flow and how long it would take a rescue victim to travel that section. The County Fire Department is currently working on similar maps.
1. Owensmouth Ave. to Reseda Blvd.
Length: 3 3/4 miles
Average peak flow: 26 feet per second or 18 mph
Travel time: 12 minutes, 30 seconds
2. Reseda Blvd. to Sepulveda Basin
Length: 1 3/4 miles
Average peak flow: 16 feet per second or 11 mph
Travel time: 9 minutes, 27 seconds
3. Sepulveda Basin to Radford Ave.
Length: 4 3/4 miles
Average peak flow: 26 feet per second or 18 mph
Travel time: 15 minutes, 50 seconds
4. Radford Ave. to I-5
Length: 6 1/4 miles
Average peak flow: 23-31 feet per second or 16-21 mph
Travel time: 19 minutes
5. Tujunga Wash
Length: 9 1/2 miles
Average peak flow: 34-38 feet per second or 23-26 mph
Travel time: 21 minutes, 42 seconds
6. Pacoima Wash
Length: 6 1/2 miles
Average peak flow: 38 feet per second or 26 mph
Travel time: 15 minutes, 59 seconds
A typical Fire Department response on “high-hazard” days--when 2 inches of rain has fallen in the mountains and/or inch in the L.A. Basin--consists of two helicopters, three engine companies, two task forces, a battalion chief, division chief and two swift-water teams. Once at the site, an appropriate rescue technique is determined and other personnel downstream are alerted. About 85% of swift-water rescues are land-based, meaning the rescuer does not get into the water.
Land-based Rescue Techniques
* “Tension diagonal line” is a rope extended diagonally across water and anchored on opposite banks at water level for victim to grab onto.
* Throw bag contains 70 feet of floatable rope and is thrown to victim.
* Rescue sling or inflated fire hose is dropped into water, usually at a bridge, to be grabbed by victim as he or she floats by.
* Rescue rocket shoots 500 feet of line at 45% angle to victim.
* Pike pole with D-shaped handles is extended for victim to reach.
Contact rescue involves firefighter entering water for rescue. Rescuer is tethered to other rescuers on-shore, pulls victim to shore or onto floating rescue board.
Helicopter lowers rescuer, who attaches harness to victim, who is raised out of water and onto land; rescuer is pulled back onto chopper.
Watercraft are sometimes used to reach victim, who is pulled onto flotation board towed behind watercraft.
Reading The River
Firefighters size up rescue situations by analyzing the river, such as how fast it’s moving, whether there are obstructions, and accessibility. Rescuers are trained in the dynamics of moving water. For example, water may appear to be moving slowly, but a rescuer knows that water speed is not constant at all depths.
Slower-moving water along shore circulates with water in middle in a circular motion, which is why a victim is often pulled to the middle and has difficulty getting back to shore.
Strainers are obstructions such as rocks, trees, or even furniture or fencing, which water flows through but a victim or rescuer can get caught in. Strainers also cause currents of different speeds and directions.
Water along shore and bottom is slowed by friction, while friction-free water in the center moves faster.
The Los Angeles City Fire Department has four swift-water teams--based in the Valley, Hollywood, downtown and Ballona Creek--consisting of six people per team. Teams are strategically placed throughout the city on high-hazard days, when heavy rain is expected. The county fire department has seven ground units and four air units specially trained in swift-water contact rescues. Rescuers are specially outfitted with gear that facilitates rescues and protects them from cold water.
Hypothermia weakens muscles and slows heart rate, which may stop if body temperature falls below 90 degrees. The L.A. River averages about 50 degrees in the winter. Below is a chart estimating how much useful work a rescuer can accomplish at varying temperatures and how long it takes to become unconscious:
Temperature: 40 degrees
Useful work: 7.5 minutes
Unconscious: 30 minutes
Temperature: 50 degrees
Useful work: 15 minutes
Unconscious: 1 hour
Temperature: 60 degrees
Useful work: 30 minutes
Unconscious: 2 hours
* Inflatable vest: whistle, knife, strobe light
* Gore-Tex dry suit or neoprene wet suit helps keep rescuer warm and dry.
* Thermal fleece layer is worn beneath dry suit.
* Some rescuers wear neoprene gloves for slippery surfaces and to protect them from cold.
* Dive booties are worn usually with fins when rescuer enters water.
Sources: Los Angeles City and County Fire Departments; U.S. Army Corps of Engineers
Researched by JULIE SHEER / Los Angeles Times