Hydrodiversity

September 5, 2018 § 4 Comments

 

I can’t stop looking at these old maps of the Los Angeles basin, from the late 1880s. Cartographic representation of the way water flowed over, under, and into the landscape approaches the expressiveness of art.

These maps depict a spectrum of conditions between dry and wet that included marshes, seeps, streams, seasonal and perennial wetlands, freshwater sloughs, arroyos, wet meadows, alkali meadows, vernal pools… Each of these hydrological conditions would have supported plants and animals uniquely suited to the resulting ecosystem.

I think of how every place in the basin interacted with water in its own particular way.

And yet these maps are only a snapshot in time. The amount of surface water in the landscape might vary according to the season, and if it was a particularly dry or wet year. In a dry year, a seep might stop flowing. After a string of wet years, it might create a small pond. During a particularly large storm, a river might shift and find a new bed.

In our current urban fabric, much of the land’s hydrodiversity has been reduced to only three basic conditions: Dry (developed) land,  lakes (reservoirs or recreational use), or stream beds (linear channels fixed in place).

What kind of hydrodiversity might urban river and stream restorations seek to create?

For more about the complex mosaic of habitat types that once existed in our basin, please see this study of the San Gabriel River and this one of the Ballona watershed.

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