Project area general description

The state of California

Are any areas excluded?

Parts of the Pit River, Sacramento R., Feather R., Ash Creek and Cottonwood Creek are excluded due to errors in the DEM.  The Legal Delta and the Tulare basin below the 220-foot contour are excluded due to inadequate DEM resolution.  Channel Islands National Park, San Nicolas, San Clemente, and Santa Catalina Islands are excluded due to missing data layers. Small portions along the state border with Oregon, Nevada and Mexico are excluded due to flow direction.

Types of flow statistics available

Peak flows statewide

ArcGIS version used for processing

Originally 9.1, with some updates using 9.2 and 9.3

Was TopoGrid used to process DEMs?

No

DEM and derivatives projection (general description)

Albers Equal Area for conterminous US; same as NHDPlus Version 1. See http://www.horizon-systems.com/NHDPlus/NHDPlusV1_documentation.php for details.

DEM and derivatives (fdr, fac, etc.) resolution

30 m

DEM source

NHDPlus V1 (NED 2004) http://www.horizon-systems.com/NHDPlus/NHDPlusV1_data.php

Hydrography source

NHDPlus V1 (1:100,000 NHD snapshot) http://www.horizon-systems.com/NHDPlus/NHDPlusV1_data.php

Hydrologic unit "walls" source

not used

Gage basin boundaries source

not used

Interactive map snapping tolerance

3 cells

Basin characteristics computed using continuous parameter grids (CPGs)

BSLDEM30M, FOREST, IMPNLCD01, JANMAXTMP, JANMINTMP, LAKEAREA, PRECIP, URBNLCD01

Name

Description

Computation Method

Data Source

ALTIND

Altitude Index, in thousands of feet. Estimated as 0.00083 times mean basin elevation.

ELEV * 0.00083

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

BASINPERIM

Basin perimeter, in miles

computed by ArcGIS

delineated basin

BSLDEM30M

Mean basin slope computed from 30 m DEM, in percent

area-weighted mean

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

CENTROIDX

X coordinate of the centroid, in map coordinates

computed by ArcGIS

delineated basin

CENTROIDY

Y coordinate of the centroid, in map coordinates

computed by ArcGIS

delineated basin

DIST2COAST

Distance in miles from basin centroid to the coast

euclidian distance from coastline grid

coastline grid converted from NHDPlus coastline features

DRNAREA

Area, in square miles

computed by ArcGIS

delineated basin

EL6000

High Elevation Index - Percent of area above 6000 feet

area-weighted mean

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

ELEV

Average basin elevation, in feet

area-weighted mean

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

ELEVMAX

Maximum elevation, in feet

maximum

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

ELEVRANGE

Elevation relief in meters

RELIEF * 0.3048

computed

FLLENMAX_M

Length of the longest flow path in meters

maximum

Flowlength grid, computed from NHDPlus fdr grid, upstream direction, http://www.horizon-systems.com/NHDPlus/

FOREST

Percentage of basin covered by forest

percent of area

2001 National Land Cover Database (NLCD) - Land Cover http://www.mrlc.gov/nlcd_multizone_map.php

IMPNLCD01

Percentage of impervious area determined from NLCD 2001 imperviousness dataset

area-weighted mean

2001 National Land Cover Database (NLCD) - Percent Impervious http://www.mrlc.gov/nlcd_multizone_map.php

JANMAXTMP

Average maximum January temperature, in degrees Fahrenheit

area-weighted mean

800M resolution PRISM 1971-2000 data  http://www.prism.oregonstate.edu/products/

JANMINTMP

Average minimum January temperature, in degrees Fahrenheit

area-weighted mean

800M resolution PRISM 1971-2000 data  http://www.prism.oregonstate.edu/products/

LAKEAREA

Percent of area covered by lakes and ponds

percent of area

2001 National Land Cover Database (NLCD) - Land Cover http://www.mrlc.gov/nlcd_multizone_map.php

LAT_OUTLET

Latitude of the outlet, NAD83

computed by ArcGIS

delineation point

MINBELEV

Minimum elevation, in feet

minimum

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

OUTLETELEV

Elevation at outlet, in feet

computed by ArcGIS

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

OUTLETX

X coordinate of the outlet, in map coordinates

computed by ArcGIS

delineation point

OUTLETY

Y coordinate of the outlet, in map coordinates

computed by ArcGIS

delineation point

PRECIP

Mean annual precipitation, in inches

area-weighted mean

800M resolution PRISM 1971-2000 data  http://www.prism.oregonstate.edu/products/

RELIEF

Relief, in feet

ArcHydro Tools COMPMETHOD=RANGE

30-m DEM, NHDPlus elev_cm grid                                http://www.horizon-systems.com/NHDPlus/

RELRELF

Relative relief - Basin relief divided by basin perimeter, in feet per mile

RELIEF / BASINPERIM

computed

URBNLCD01

Percentage of urban land cover determined from NLCD 2001 land cover dataset

percent of area

2001 National Land Cover Database (NLCD) - Land Cover http://www.mrlc.gov/nlcd_multizone_map.php