California Code of Regulations › Title 23 - Waters › Division 2 - Department of Water Resources › Chapter 1 - Dams and Reservoirs › Article 6 - Inundation Maps › Section 335.2 - Definitions

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
(a)
				  Unless the context clearly requires otherwise, as used in this article, the
				  terms below shall have the meanings noted:
(1)
				  "Breach" refers to an opening through a dam or critical appurtenant
				  structure.
(2) "Breach height"
				  refers to the vertical distance of the dam or critical appurtenant structure
				  that must be breached in the model. The breach height of a dam shall be
				  measured from the upstream toe or downstream toe, whichever elevation is
				  higher, to the maximum possible storage elevation. The breach height of a
				  critical appurtenant structure is its height, as defined in section
				  335.2(a)(3)(B).
(3) "Critical appurtenant structure" refers
				  to a barrier or hydraulic control structure that impounds the same reservoir as
				  the dam and is 25 feet or more in height, impounds a minimum of 5,000 acre-feet
				  of water at the maximum possible storage elevation, or that the department
				  determines poses a significant or higher downstream hazard potential per
				  section 335.4(a). Typical
				  critical appurtenant structures include emergency spillways, gated spillways,
				  and saddle dams.
(A) A critical appurtenant
				  structure may contain multiple water barriers, including but not limited to
				  gates, flashboards, and concrete monoliths.
(B) The height of a critical appurtenant
				  structure shall be measured from the upstream toe or downstream toe, whichever
				  elevation is higher, to the maximum possible storage elevation, except for the
				  following cases:
1. For a structure
				  comprising gates constructed on a concrete control structure, such as a
				  spillway with multiple radial gates, its height shall be measured from the
				  upstream toe of the concrete control structure to the maximum possible storage
				  elevation.
2. If gates are affixed
				  to a concrete dam, the height shall be measured from the base of the gates to
				  the maximum possible storage elevation.
(C) A penstock or low-level outlet shall be
				  considered a critical appurtenant structure if the department determines it
				  poses a significant or higher downstream hazard potential, as defined in
				  section 335.4(a).
(4) "Critical facilities" refers to law
				  enforcement facilities, fire stations, schools, hospitals, prisons, and major
				  roads.
(5) "Dam" has the same
				  meaning as provided in section
				  6002 of the
				  Water Code.
(6) "Dam system" refers
				  to a dam and all critical appurtenant structures that impound the same
				  reservoir.
(7) "Dynamic routing"
				  refers to hydraulic flow routing based on the shallow water equations to
				  compute changes in discharge, velocity, and stage with respect to time at
				  various locations along a watercourse.
(8) "EAP" refers to an emergency action plan
				  as described in section
				  8589.5 of
				  the Government Code.
(9) "Failure
				  scenario" refers to the modeled simulation of a breach of a dam or critical
				  appurtenant structure that results in an unintended release of the
				  impoundment.
(10) "FEMA P-946"
				  refers to the Federal Emergency Management Agency's "Federal Guidelines for
				  Inundation Mapping of Flood Risks Associated with Dam Incidents and Failures,"
				  dated July 2013.
(11) "Flood wave
				  arrival time" refers to the elapsed time from the initiation of the failure
				  scenario until the arrival of the leading edge of the flood wave.
(12) "Geospatial file" refers to a digital
				  file containing data that is geographically referenced, typically in vector or
				  raster format, as projected in NAD 1983 Teale (California) Albers per section
				  335.12(g).
(13) "Hydraulic model" refers to a computer
				  model used to simulate the spatial and temporal changes of water depth and
				  velocity conveyed through a watercourse.
(14) "Hydrograph" refers to a graphical
				  representation of flow as a function of time.
(15) "Inundation area" refers to the area
				  downstream of the dam or critical appurtenant structure that would experience a
				  rise of one foot or greater in water surface elevation as the result of a
				  failure scenario.
(16) "Inundation
				  boundary" refers to the perimeter of the inundation area.
(17) "Inundation map" refers to a map showing
				  the impacts of a failure scenario, such as where and when flooding would occur,
				  and may contain multiple sheets.
(18) "Inundation map sheet" refers to a page
				  in an inundation map.
(19) "Maximum
				  possible storage elevation" refers to the maximum reservoir elevation to which
				  water can be physically impounded without spilling. In most cases, this is the
				  certified storage elevation. When a reservoir is restricted below the spillway,
				  this is the elevation of the spillway crest.
(20) "NAVD88" refers to the North American
				  Vertical Datum of 1988 computed by the National Geodetic Survey.
(21) "Owner" has the same meaning as provided
				  in section
				  6005 of the
				  Water Code.
(22) "PDF" refers to a
				  portable document format file.
(23)
				  "Projection" refers to a method by which the curved surface of the Earth is
				  portrayed onto a flat surface.
(24)
				  "Raster" refers to a data format that represents geographic information as a
				  grid of cells, where each cell contains a value.
(25) "Storm-induced loading condition" refers
				  to the meteorological conditions before and during the modeled breach of the
				  dam or critical appurtenant structure when the reservoir is at or above the
				  maximum possible storage elevation and the inundation boundary is greater than
				  that of a sunny-day loading condition due to a rain or flood event.
(26) "Sunny-day loading condition" refers to
				  the meteorological conditions before and during the modeled breach of the dam
				  or critical appurtenant structure at the maximum possible storage elevation
				  with non-flood season inflow.
(27)
				  "Toe" refers to the junction of the slope of a dam or critical appurtenant
				  structure with the natural ground surface.
(28) "Two-dimensional hydraulic model" refers
				  to a hydraulic model in which variables such as velocity and depth vary in two
				  horizontal directions along a watercourse.
(29) "Vector" refers to a data format that
				  represents geographic information as point, line, or polygon
				  features.