Impacts of Development
California Coastal Commission
Mission Resource Conservation District
State Water Resources Control Board
Local Government Commission
Department of Water Resources
National Oceanic and Atmospheric Administration
UC and USC Sea Grant
Linking Land Use to Water Quality
For more information, contact the CA NEMO Partnership:
The California NEMO Partnership is an educational program for land use decision makers that addresses the relationship of land use to natural resource protection.
© The University of Connecticut. Adapted with permission of the University of Connecticut Cooperative Extension System.
Disruption of the Water Cycle
Impacts on Stream Form and Function
These readily apparent physical changes result in less easily discernable damage to the ecological function of the stream. Bank erosion and severe flooding destroy valuable streamside, or riparian, habitat. Loss of tree cover leads to greater water
All of this, of course, assumes that the streams are left to adjust on their own. However, as urbanization increases, physical alterations like stream diversion, channelization, damming and piping become common. As these disturbances increase, so does the ecological damage the endpoint being a lifeless stream completely encased in concrete channels and underground pipes. In addition, associated habitats like ponds and wetlands may be damaged or eliminated by grading and filling activities.
Then Theres Water Quality
The Total Picture: A System Changed
for the Worse
The end result is a system changed for the worse. Properly working water systems provide drainage, aquatic habitat, and a degree of pollutant removal through natural processing. Lets look at those functions in an urbanized watershed where no remedial action has been taken:
Drainage: Increased runoff leads to flooding. Drainage systems that pipe water off-site often reduce flooding at that particular locale at the expense of moving flooding (and erosion) problems downstream. Overall system-wide water drainage and storage capacity is impaired
Habitat: Outright destruction and physical alteration of steams, increased pollution, and wide fluctuations in water quality conditions (such as volume, clarity, and temperature) all combine to degrade habitat and thus reduce the numbers and types of aquatic and riparian organisms. In addition, waterway obstructions like bridge abutments, pipes, and dams create barriers to wildlife migration.
Pollutant removal: Greater pollutant loads in the urban environment may overwhelm the ability of natural processes to remove pollutants. Damage to river banks, streams, and wetland vegetation further reduces their ability to naturally remove pollutants. Finally, the greater volume and irregular (flashy) pulses of water caused by storm events impair natural pollutant removal processes by decreasing the time that water is in the system.
What Communities Can Do
To begin to truly address the impacts of urban growth, local officials need to look at their waterways as a valuable community resource as well as an interconnected water conveyance system. They also need to recognize the fundamental changes that development can bring to the water cycle, stream form and function, aquatic ecology, and water quality. Incorporating this understanding into local land use decisions will help to guide environmentally safe growth. There are a number of options that can be employed to reduce the impacts of development on water quantity and quality. Preventing such impacts in the first place is the most effective (and cost efficient) approach, and should always be emphasized. To this end, municipal officials should consider a three-tiered strategy consisting of natural resource based planning, appropriate site design, and stormwater treatment.
The California NEMO Partnership is a charter member of the National NEMO Network.