Hydrology
Sacramento County contains a large network of waterways including drains, culverts, creeks, sloughs and rivers that collectively receive and covey stormwater and agricultural and urban runoff from throughout the County to the Sacramento/San Joaquin River Delta and to the San Francisco Bay. Because of the large number of water courses in Sacramento County and the County’s relatively flat terrain it is important to maintain an efficient drainage network in order to avoid negatively affecting existing drainage patterns, avoid increasing flood elevations in flood zone areas and creating new flood hazards.
The California Environmental Quality Act Guidelines (Guidelines) include instances when hydrological impacts might result from a project. Appendix G of the Guidelines details that impacts may occur when:
- an existing drainage pattern is substantially altered,
- the rate or amount of runoff increases in a manner that would result in flooding,
- a project is developed within the 100-year floodplain,
- structures are placed in a manner that would impede or redirect flows within a 100-year floodplain,
- people or structures are exposed to a substantial risk of loss, injury or death involving flooding; and
- when runoff is created or contributed to that would exceed the capacity of stormwater systems.
Floodplains and flood issues are regulated and addressed by the provisions of the Sacramento County Floodplain Management Ordinance, Improvement Standards, and Local Floodplain Management Plan as well as state and federal regulations. As part of the County’s planning and environmental review process for new development projects, an analysis of impacts related to hydrology and flooding may be required and measures to minimize those impacts may be necessary.
For additional information related to hydrology and flooding please refer to the following resources:
Water Quality
Before the Sacramento area was developed, most rainfall fell onto natural areas and the water soaked into the ground where waters were naturally filtered before entering watercourses or subsurface water supplies.
Now that the landscape in Sacramento has changed and become more developed, stormwater flows are able to more quickly run directly into street gutters and drains that carry run off, in many instances, directly to creeks. The fast moving urban runoff can pick up pesticides, fertilizers, sediment, oil and many other pollutants that are commonly found in urban settings and can result from construction related activities and can carry them to the creeks and rivers where they can negatively affect waters utilized for municipal water supplies, agriculture, recreation and wildlife habitat.
The California Environmental Quality Act Guidelines (Guidelines) include instances when water quality impacts might result from a project. Appendix G of the Guidelines details that impacts may occur when substantial sources of polluted runoff are created or when sources of pollution are created that substantially degrade ground or surface water quality.
Water quality issues are regulated and addressed by the provisions of the National Pollution Discharge Elimination System Municipal Stormwater Permit issued to Sacramento County by the Central Valley Regional Water Quality Control Board, the County’s Stormwater Pollution and Erosion Control Ordinance, the County’s Stormwater Management and Discharge Control Ordinance, the County’s Land Grading and Erosion Control Ordinance as well as state and federal regulations. As part of the County’s planning and environmental review process for new development projects, an analysis of impacts related to water quality may be required and measures to minimize those impacts may be necessary.
For additional information related to water quality please refer to the following resources:
