Most cities are not well integrated into the local hydrologic regime, and Berkeley is no exception. Fields and forests soak up rainwater like a sponge and slowly release water into streams. But with urban development, rain hits roofs, roads and parking lots and immediately gets routed away through pipes and culverts, picking up speed and pollutants as it flows downhill, and eventually dumping directly into creeks and the bay.
Common effects of urbanization on stream ecosystems are sometimes described as the "urban stream syndrome". Symptoms of urban stream syndrome include:
- a flashy hydrograph (flash floods, quick pulses of water in creeks)
- high concentrations of nutrients and contaminants
- altered channel morphology and stability
- reduced biotic richness, with increased dominance of invasive tolerant species
One of the main cures for urban stream syndrome is a range of techniques called Low Impact Development.