Affectionately known to locals as simply "the Arroyo", the Arroyo Seco has been treasured by residents of the San Gabriel foothills for centuries. Known as the birthplace of Pasadena, the Arroyo has factored prominently into the culture of the first people to seek refuge at the base of the San Gabriel Mountains to the present day urban communities. Today, we admire the Arroyo's beauty, celebrate its ecological diversity, and protect its heritage. Recently included in the National Register of Historic Places, the Arroyo has been identified as one of America's top cultural resources. For more information, visit City of Pasadena's City Heritage webpage.
As early as 1887, the citizens of Pasadena recognized the land surrounding the Arroyo Seco should become a park for the enjoyment and benefit of the public. It is claimed President Theodore Roosevelt visited the Arroyo Seco in 1911 and is quoted as saying, “This Arroyo would make one of the greatest parks in the world." Between 1911 and 1927, the City of Pasadena accumulated the land for what is now the Central and Lower Arroyo. In 1919, the area now known as Hahamongna Watershed Park was annexed to the city by popular vote. The land was then leased to the County of Los Angeles for the construction of Devil's Gate Dam as well as for the mainteneance of a reservoir for water conservation and flood control purposes.
In 1918 the Arroyo Park Committee, headed by architect Myron Hunt, suggested that a comprehensive plan be developed by noted landscape architect Emile Mische. The plan recommended that the Lower Arroyo be reserved for trails and bridle paths and planted only with native plants. In 1977, the City declared the Lower Arroyo to be a City Cultural Landmark. In the last two decades of the twentieth century, the City of Pasadena began the process of resuming management of the area north of Devil's Gate Dam and converting it from a land of harvest and production to protected parkland. The land was named Hahamongna Watershed Park.
In the late 1990’s the City of Pasadena, in partnership with community members, engaged in a visioning process to develop the Arroyo Seco Master Plans . The plans define a community vision for the preservation, management, and restoration of the Arroyo Seco Natural Park--a park incorporating all three park areas into one. The Arroyo Seco Master Plans were adopted by City Council between the years 2003-2005. After years of park planning and development, the Arroyo Seco Natural Park totals nearly 1,000 acres today, distinguishing it as Pasadena’s largest and most diverse park. No doubt, President Roosevelt would be very pleased to see the great park this land became.
The land now famous for the Tournament of Roses, the Rose Bowl, the Jet Propulsion Laboratory, and California Institute of Technology, was once occupied by the Tongva. Subsisting on local game and vegetation, the Tongva lived in villages scattered along the Arroyo Seco and the canyons from the mountains down to the South Pasadena area.
The Tonga have a long history as stewards of this land. Each year, following the seasons, they collect botanical material for traditional spiritual, ceremonial, medicinal and utilitarian uses. As guardians of these natural resources, they understand how to collect in a way that does not impair the sustainability of the plant population. As custodians of their culture, individuals, families and tribal groups use sites throughout Hahamongna Watershed Park for spiritual, social, and ceremonial traditions.
Built in 1913, the Colorado Street Bridge gracefully rises 150 feet above the Arroyo Seco stream connecting Pasadena with the Eagle Rock community to the west. Known for its distinctive Beaux Arts arches, the bridge significantly reduced the time required to cross Arroyo Seco canyon. In 1981 the bridge was added to the National Register of Historic Places.
Originally built in 1920, and later reinforced in 1998, this is the first dam built for Los Angeles County’s flood control and water conservation system. Its name is derived from a unique rock formation below the dam that resembles the profile of a horned devil. In 1858, when Judge B.S. Eaton visited the site of the Arroyo Seco, he named the location “the Devil’s Gate.” The formation has since been covered during restoration of the dam and is no longer visible.
This bridge, built of sustainable materials and opened in 2007, offers year-round access for pedestrians, equestrians and bicyclists to a full trail loop around the Hahamongna basin.
Large basins in the bed of the stream can be found on the eastern side of Hahamongna Watershed Park flood basin. These spreading basins are used by the City of Pasadena to recharge the aquifer with water from the Arroyo Seco stream. The aquifer contributes to much of the municipal water supply.
South of the Colorado Street Bridge are several low-flow streams. These streams were constructed in 1997 as part of a restoration effort in the Lower Arroyo, and mimic what the area resembled prior to construction of the flood control channel. Willows and other riparian vegetation flourishing along the streams provide habitat for several native species.
In the center of the Lower Arroyo is the Memorial Grove. Planted with a variety of native tree species, the Memorial Grove commemorates community members who have passed on.
Toward the southern end of the Lower Arroyo, the Camel’s Hump rises from the Arroyo Floor. Once a spur ridge deflecting the Arroyo Seco’s natural flow pattern, the “hump” was split in two during the construction of the Arroyo Seco storm channel.