Piedmont’s five creeks and their tributaries carve small ravines and valleys as they flow from the hills into what is now Lake Merritt, and eventually, the San Francisco Bay. The area became more urbanized in the early 1900s. By the 1930s, most of these waterways were culverted or channelized. They now flow largely through underground pipes rather than natural channels. A few above-ground segments (“daylighted”) remain in parks and older open-space corridors. Most of the daylighted sections of the creeks aren’t contiguous. Still, even when invisible, these creeks continue to shape local hydrology and topology, carrying rainfall and runoff toward Lake Merritt and the San Francisco Bay and causing landslides and slumping.

Undergrounding Piedmont’s creeks permitted houses to be built, but it also caused long-term damage to the environment that’s visible today. These problems are well documented (cite), and include:

• Creeks that aren’t permitted to flow naturally pick up urban pollutants more quickly (oil, metals, lawn chemicals) and send them directly into bays, estuaries, or lakes. Piedmont’s creeks are polluted (link to data)

• Pipes and concrete channels raise water temperature, harming aquatic life downstream. Piedmont’s creeks have unnaturally high temperatures (link to data)

• Hard-lined channels move water faster, damaging land around the creeks and causing landslides and even flash-floods downstream (link to photos)

• Underground creeks become biologically dead: no plants, insects, fish, amphibians, or birds that rely on riparian corridors. This is true of Piedmont’s creeks (link to data)

• Tree loss along the creeks lessens natural cooling and shade, making neighborhoods hotter (“urban heat island” effect).

• Pipes stop creek water from recharging water aquifers.