The main drainage in the watershed is Novato Creek. Novato Creek is joined by six major tributaries along its 17 mile length:
- Leveroni Creek
- Bowman Canyon
- Warner Creek
- Arroyo Avichi
- Arroyo de San Jose
- Simmons Slough
The Novato Creek watershed supports diverse habitats from steep headwaters to salt marshes along the bay. The creek flows through oak and bay forests, grasslands, and baylands. The marshes ringing the bay are some of the largest remnants left in the bay. They support abundant waterfowl populations.
Despite being one of the driest in Marin County, the watershed supports both rearing and spawning steelhead salmon. Diked baylands within the watershed provide seasonal wetland habitat for migratory ducks and shorebirds. These lands also contain oak woodlands that provide habitat for terrestrial wildlife species.
The upper watershed is composed of annual grasslands, oak-bay woodland, and oak savanna. There are patches of northern coastal scrub in the woodlands and serpentine outcroppings in the upper elevations in the north. The healthiest riparian forests are in the upper watershed along Novato Creek and Arroyo San Jose.
One of the best examples of a healthy riparian community is at O’Hare Park at Novato Road and San Marin. Its riparian plant community is structurally diverse and supports a mixture of native species. Large woody debris is left in place by the City of Novato enhancing instream habitat for fish and frogs.
In the lower watershed, oak woodland and oak savanna are more prevalent. The lower reaches of Novato Creek east of Highway 101 support brackish-water and saltwater marsh marsh inundated twice a day by the tides. Freshwater seasonal wetlands occur behind levees that were once historical tidal marsh. These areas have been diked off to provide agricultural land and flood protection and some still support oat hay production.
The Novato Creek watershed supports many special status plants and animals. Of particular interest are the wetland species along Rush Creek and lower Novato Creek.
Noteworthy species include:
- San Pablo song sparrow
- California black rail
- Saltmarsh common yellowthroat
- Salt marsh harvest mice
- California Ridgway's rail
- Western pond turtles
- Naturalized bullfrogs
The Novato Creek watershed supports at least 10 extant fish species. Native species include:
- California roach
- Sacramento pikeminnow
- Sacramento sucker
- Threespine stickleback
- Prickly sculpin
Introduced species include:
- Rainwater killifish
- Western mosquitofish
- Striped bass
- Green sunfish
The watershed once supported native tidewater goby but the last collection occurred in 1945.
The presence of these non-native fish have also been noted:
- Largemouth bass
- Brown bullhead
- Chameleon goby
- Inland silverside
Salmonids (steelhead and Chinook salmon) are also found within the Novato Creek watershed. According to California Department of Fish & Wildlife, Chinook salmon are likely strays from the Sacramento River system. A net pen release site for the Sacramento River Chinook is located in Tiburon, which could result in fish moving into Marin streams.
There are no reported occurrences of foothill yellow legged frogs within the watershed. California red-legged frogs occur in ponds and tributaries of Novato Creek.
Audubon Canyon Ranch has been monitoring Heron and egret nesting colonies since the early 1990s. There are two active and one inactive heronries within the greater Novato Creek watershed.
Avian surveys were conducted over a 1,300 meter reach from Diablo Avenue to Grant Avenue during the 2006 nesting season as part of the Novato Flood Control Project.
- 65 avian species were detected
- 27 species were confirmed nesting or thought to be nesting on site
- 12 more species were suspected but not confirmed
Noteworthy species include:
- Great blue heron
- Cooper’s hawk
- Allen’s hummingbird
- Purple martin
- Oak titmouse (nesting)
- Nuttall’s woodpecker (nesting)
The development of Novato leveled off between 1990 and 2000. It then increased and as a result, Novato was the fastest growing city in Marin in 2005. It is anticipated to continue to grow. Over the next 20 years the City expects greater growth in jobs than population. This will lower the percentage of the population that commutes to other places for work.
Novato is actively engaged in downtown redevelopment. There is proposed development of commercial and residential uses and supporting infrastructure. The Marin Countywide Plan identifies Novato as having the greatest potential in Marin for commercial and industrial growth.
Changes to the watershed
Novato Creek watershed’s channels have been changed from their historic natural conditions. Today’s channels reflect those alterations and many are unstable. Most channels are narrower than expected for the watershed size. Increased rainfall and impervious surfaces are also sending more water to the creeks at a faster rate.
Extensive bank erosion indicates that the channels are in a widening phase. Sediment enters the creek from landslides and gully development uphill, as well as channel bed incision and bank erosion.
Within City limits, the mainstem of Novato Creek and its major tributaries are all constrained by development on the banks. Channels in the upper watershed are still incising and are expanding headward into hillside swales.
The channels in the lower watershed are managed for flood conveyance and navigation. They no longer transport sediment. Sediment accumulation in this area is a natural process to re-establish a stable channel based on rain, slope, and sediment supply.
Restoration and conservation
Land protection and restoration efforts in the watershed include:
- Hamilton Wetland Restoration project
- Rush Creek restoration project
- Bahia restoration project
- Planning by the City of Novato and Marin County Open Space District for preservation and land acquisition for trails
- Novato Creek Bank Stabilization Guidelines
- Personal communication, M. Fawcett to L. Lewis
- Novato Creek EIR - Phase VIII flood control project
- Ecology, Assemblage Structure, Distribution & Status of Fishes in Streams Tributary to the San Francisco Estuary
- Letter: Novato Flood Control Project, Phase VIII; Fish Salvage and Relocation
- California Department of Fish and Game (CDFG). 2008. California Natural Diversity Database
- Annotated Atlas and Implications for the Conservation of Heron and Egret Nesting Colonies in the San Francisco Bay Area