Nature’s Notebook: When water becomes a problem

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While it’s true that rain is critical for all living things on Catalina, it’s sometimes possible to have too much of a good thing. The problem isn’t that we get too much water; it’s that we get too much water too quickly.

1995 storms packed a punch

The storms of 1995 are a classic example. These storms were not the largest recorded on Catalina, yet they were responsible for some of our worst flood damage ever. Here’s why.

While it’s true that rain is critical for all living things on Catalina, it’s sometimes possible to have too much of a good thing. The problem isn’t that we get too much water; it’s that we get too much water too quickly.

1995 storms packed a punch

The storms of 1995 are a classic example. These storms were not the largest recorded on Catalina, yet they were responsible for some of our worst flood damage ever. Here’s why.

In 1995, we experienced a number of good, small rain events. Then on December 5, a large storm dropped 4.7 inches in Middle Ranch. This effectively filled Middle Ranch Reservoir to the brim. Then on December 11, a second intense storm quickly dropped an additional 5.2 inches of water in Middle Ranch.

With the reservoir already full, large quantities of excess water spilled over the dam, forcing a torrent of water downstream.

This wall of water changed the course of the drainage below, shifting it dangerously close to the Eagle’s Nest Lodge, destroying Middle Ranch Road, and forcing masses of soil, boulders and debris downstream.

By the time the flood reached Ben Weston Road, it blew through the watershed, taking that road with it, too. This rain-driven event had an economic impact in the millions of dollars, and dramatically changed the landscape of Catalina.

Rainy day highs and lows: 1948 to today

The following statistics were taken from a weather database that tracked rainfall from 1948 to 2006 for most weather stations.

The most rainfall recorded in Avalon on a single day was seven inches on Dec. 6, 1966. The most rainfall recorded on a single day in Middle Ranch was 6.14 inches on Nov. 30, 1970.

The most rainfall recorded on a single day at El Rancho Escondido was 4.3 inches on November 15, 1965.

The Airport in the Sky receives 1.71 inches more rain on average than Avalon per year. That may not seem like a big difference, but it adds up. From 1948 to 2006, the airport received 101.44 inches more in rainfall than Avalon!

El Rancho Escondido gets 3.40 inches less annual rainfall on average than Avalon. From 1948 to 1993, Escondido received a total of 150.02 inches less rain than Avalon!

If you look closely at the habitats around Avalon, the Airport in the Sky, and El Rancho Escondido, you’ll notice that the vegetation is significantly different in each of these locations. Differences in rain and fog have a lot to do with that.

For the record: The record year for the most rain, Island-wide, was 2004, when the average from various locales was 26.80 inches of rain.

The record year for the least amount of rain was 1960, when the average was only 3.445 inches of rain. That’s only about one quarter of our annual average rainfall of about 12 inches.

Special thanks to Frank Starkey and Denise Knapp for data.

Rich Zanelli and Katelyn Horn contributed to this story

Frank Hein is director of education for the Catalina Island Conservancy.

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