The Los Angeles River is composed of a series of riparian and estuarine environments. These urbanized riverbanks vary, from vertical box channels to steeply sloped trapezoidal profiles. The headwaters of the river begin in the San Fernando Valley, a landscape constituted of grasslands and dry upland chaparral woodlands from the foothills and canyons of the San Gabriel, Santa Monica, and Verdugo mountain ranges. This landscape of the valley was once characterized by extremely well-draining soils which led to the upper portions of the river occasionally disappearing during dry months. The river would re-emerge as it approached the bedrock of the Santa Monica Mountains owing to the underlying geology. While most of the river bottom today is concrete channel, the river transitions to a soft vegetated bottom as it makes its way around Griffith Park at the Glendale Narrows. The softer portions of the river create valuable feeding and rest areas for local and migratory birds.1 Historically the majority of the river was part of a large alluvial grassland plain punctuated by riparian stands of cottonwood and willows. Where the mouth of the river reaches Long Beach, the landscape was once a marshy estuary, teeming with migratory and nesting birds. These estuarine areas comprised a tallgrass marsh of freshwater, brackish and eventually saltwater aquatic ecosystems.
A comparative study of the path of the Merced River was conducted as a natural analog to the Los Angeles River’s urbanized character. This study provides a benchmark for the consideration of ecological communities, riparian structure and hydrological flow. This river runs from Yosemite down into the fertile San Joaquin Valley. It travels from rocky terrains to dry foothills eventually emptying out into an agrarian coastal plain. While the Merced has many similar plant communities and physical terrains to the LA River before it was channelized, the Merced does not connect to the Pacific and lacks the estuarine landscape.