Geography 85
Applications on GeoSpatial Technology

 

Primer on Dry Creek Watershed -
Secret Ravine Management Plan

Location:

Western Placer County (Loomis, Rocklin, Roseville)

Major Goals:

Habitat restoration (vegetative, fish, wildlife), water quality improvement, storm water management and flood protection

Sample Language from Secret Ravine Adaptive Management Plan (AMP)

Promote projects to protect and enhance anadromous fishery and riparian corridors

Promote optimal passage of stormwater to:

Critical Fish Habitat its Importance

Central Valley riparian forests have been dramatically reduced since pre-Gold Rush days (about 1% of former acreage). In addition, approximately 1200 major dams exist in California. Federal and State water projects, such as the Shasta Dam and Oroville dam, have completely blocked passage of sea-going fish to their native spawning grounds. Consequently, every spawning stream, whether a mountainous clear running stream or a degraded urban channel, is of great value. Land managers and agencies have spent millions toward protecting and improving what is left of this limited resource. Dry Creek Watershed is one of those watersheds. Salmon still make a fall run up Secret Ravine, sometimes sighted at the Rocklin Road bridge (adjacent to Sierra College). One of the most important habitat factors in a healthy stream system is gravel beds or a clean river bottom (strata) free of sediment. In addition, riffles (cascading gravel beds, aerating the water) provide ideal conditions for bugs to live beneath rocks and provide food for fish. Riparian canopy and vegetation is identified as another key component of healthy habitat for fish, providing shade to keep water temperatures down (and oxygen levels higher) and supply debris that will fall into the stream. Streamside vegetation prevents bank erosion. Both factors provide hiding places for juvenile fish and thus help sustain a population.

Water Quality & Stream Health

The State of California and other agencies are increasingly concerned about water quality. Our limited water supply is easily contaminated by urban development and agriculture. One major contributing factor is run-off during precipitation events, which is commonly referred to as non-point source (NPS) pollution. Impervious (or hardened) surfaces greatly add to this problem. Basically heavy rains cannot be absorbed effectively (where once loose soil and vegetation did the job). Instead, storm water rapidly flushes into storm drains or directly into the stream. Peak water flows carry pollution (oil residue, industrial chemicals, or whatever toxic substances lies on the pavement) directly into the stream.

A popular way to determine the health of a stream today is to sample aquatic insects, which can indicate which type of insects belong in certain sections (upper reaches, mid reaches, etc.) of a stream system. In certain sections, some bugs can tolerate poor conditions while others normally found there cannot survive. Coupled with water sampling for chemical analysis, this is a strong indicator of stream health and is used widely today. Thus the need to track bug populations and their locations.

Storm Water Management & Flood Protection

As mentioned above, paved surfaces do not allow soil and vegetation to absorb storm water. Consequently storm water sheets up and accumulates in great quantities on parking lots, paved streets, sidewalks, driveways, even semi-impermeable surfaces such as gravel lots. All of this water enters the stream at once, often creating flash flooding conditions. The consequences have a dramatic impact on the stream system, such as: surface erosion, sedimentation, bank erosion, deepening of channel, simplification of a channel (less oxbow and marshy areas), reduction of riparian vegetation (through erosion), and many other non-intended consequences.

There are many ways to remedy these problems, such as providing buffer areas to give storm water a chance to percolate back into the ground. Other solutions include holding basins, sophisticated public works solutions (that I'm unable to explain), or simply reducing impervious cover for each subwatershed unit that drains into the main stream. But unless the problems are identified on GIS maps, often these problems are overlooked and compounded downstream.

Next Lecture - Putting Together a GIS - Part II


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