The developed landscapes
found in urban areas introduce a number of factors that can affect the health of nearby streams, rivers, and lakes. Roads and other paved surfaces, sewer
systems, gardens and parks, industrial facilities, and storm water management systems mark the landscape. These cause significant changes in how water
flows across the landscape and on the content of that water. Stormwater runoff in urban areas can pick up sediment, oils and chemical residue from our
cars and streets; bacteria and nutrients from pet waste; and pesticides and nutrients from lawns and gardens. These pollutants can harm fish and wildlife
populations, compromise native vegetation, and degrade water quality.
Buildings, paved parking lots and roads are hard, impervious surfaces which control how water is transported to urban streams. In an urban setting,
rain and snowmelt cannot penetrate the hard surfaces and soak into the ground.
Instead, stormwater drains directly to storm drains, streams, or other surface water bodies. Typically the volume and velocity of surface water are higher
in urban areas than in undeveloped areas. This can alter the natural drainage patterns and change the physical
habitat of streams.
Often streams that flow through our cities and towns have lost many of the adjacent trees and shrubs that provide shade and streamside (riparian) habitat.
The loss of riparian vegetation may increase water temperature above that which is healthy for fish and other native species that live in the streams.
can greatly impact stream health. Plowing, pesticide application, irrigation, fertilizing, planting, and harvesting can introduce pollutants into
nearby streams. Confined animal facilities (e.g., feedlots, dairies), and grazing can also be a source of pollution. Excess sediment, nutrients, pathogens,
pesticides, and salts are commonly found pollutants in waters adjacent to and downstream of agricultural areas.
Grazing cattle can eliminate riparian vegetation, trample steam bank and bottom habitat, and compact the soil, making
it harder for rainfall to infiltrate soils and move into groundwater basins.
Instead, more water flows directly into streams. Some natural drainages are channelized to provide water for irrigation or to move agricultural runoff
away from fields. Increased
flow volume and velocity can alter the natural drainage patterns and change the physical habitat of streams.
endowed with magnificent natural landscapes. Redwood forests, deserts, chaparral are all signature California landscapes. Large areas within the state
are relatively undisturbed when compared to the state’s cities, towns, and agricultural areas. These undeveloped areas are subject to fewer of
the stresses we find in developed settings. The degree to which human activities influence stream health varies depending on the land use. Dirt roads
that support timber harvesting can be a source of excessive fine sediment in our streams. Invasive plants may change the biological composition of native
habitats. Mining activity can pollute streams. Careful land management can help preserve the health of these streams.
Land Use Related stream diagrams from the US Geological Survey (USGS)
Please Note: some specific fish or aquatic insect species pictured & described here may not occur in California streams.
USGS Circular 1391, Published 2013 'The Quality of Our Nation's Waters Ecological Health in the Nation's Streams, 1993-2005 [Chapter 2, pages 30-35]'
How do we measure the influence of land use?
Land use is an important driver of stream health and land use type often correlates directly with stream condition. The Perennial Streams Assessment
(PSA) looked at the relationship between the overall condition of our streams and nearby land uses.