Project area general description

The state of Alabama

Are any areas excluded?

No

Types of flow statistics available

peak flows only (all three reports)

ArcGIS version used for processing

Originally 9.1, with some updates using 9.2 and 9.3

Was TopoGrid used to process DEMs?

Yes

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

10 m

DEM source

10-meter NED (http://ned.usgs.gov/) circa 2011

Hydrography source

National Hydrograpy Dataset (NHD) http://nhd.usgs.gov/

Hydrologic unit "walls" source

WBD

Gage basin boundaries source

not used

Interactive map snapping tolerance

3 cells

Name

Description

Computation method

Data source

Report

Variable label in report

CONTDA

Contributing Drainage area in square miles

polygon area

GlobalWatershed

Magnitude and Frequency of Floods on Small Rural Streams in Alabama (T.S. Hedgecock)

A

URBAN

Percentage of urban land cover determined from NLCD 2006 land cover dataset (note correction equation in xml additional params)

percent of area

NLCD 2006, codes 21-24 http://www.mrlc.gov/nlcd01_data.php

Magnitude and Frequency of Floods for Urban Streams in Alabama, 2007 (T.S. Hedgecock and K.G. Lee)

PD

LC11IMP

Percentage of impervious area determined from NLCD 2011 impervious dataset

area-weighted mean

NLCD 2011 imperviousness grid http://www.mrlc.gov/nlcd01_data.php

LC11DEV

Percentage of urban land cover determined from NLCD 2011 land cover dataset

percent of area

NLCD 2011, codes 21-24 http://www.mrlc.gov/nlcd01_data.php

LC06DEV

Percentage of urban land cover determined from NLCD 2006 land cover dataset (note correction equation in xml additional params). Mimic of URBAN and retained as a legacy attribute

percent of area

NLCD 2006, codes 21-24 http://www.mrlc.gov/nlcd01_data.php