TABLE B1. Landcover variables.

Variable

Definition

 Basin land cover

P_NLCD1

Aggregated NLCD 2001 "level 1" category: water (% basin area)

P_NLCD2

Aggregated NLCD 2001 "level 1" category: developed (% basin area)

P_NLCD3

Aggregated NLCD 2001 "level 1" category: barren (includes all level 2 barren and
unconsolidated categories) (% basin area)

P_NLCD4

Aggregated NLCD 2001 "level 1" category: forest (% basin area)

P_NLCD5

Aggregated NLCD 2001 "level 1" category: shrubland (includes all level 2 shrub and
scrub categories)(% basin area)

P_NLCD7

Aggregated NLCD 2001 "level 1" category: herbaceous upland natural/semi-natural
vegetation (grassland) (% basin area)

P_NLCD8

Aggregated NLCD 2001 "level 1" category: crops and pasture (% basin area)

P_NLCD9

Aggregated NLCD 2001 "level 1" category: wetlands (% basin area)

NLCD_IS

NLCD 2001 mean percent impervious surface in the basin

NOAA_IS

Mean percent impervious surface in the basin derived from NOAA 1 km resolution data
for 1990s (see http://dmsp.ngdc.noaa.gov/html/download_isa2000_2001.html)

Distance weighted land cover

pWATERdw

Aggregated NLCD 2001 "level 1" category: water (% basin area, weighted by distance
from sampling site)

pURBANdw

Aggregated NLCD 2001 "level 1" category: developed (% basin area, weighted by
distance from sampling site)

pBAREdw

Aggregated NLCD 2001 "level 1" category: barren (includes all level 2 barren and
unconsolidated categories) (% basin area, weighted by distance from sampling site)

pFORdw

Aggregated NLCD 2001 "level 1" category: forest (% basin area, weighted by distance
from sampling site)

pRANGEdw

Aggregated NLCD 2001 "level 1" category: shrubland (includes all level 2 shrub and
scrub categories)(% basin area, weighted by distance from sampling site)

pHERBw

Aggregated NLCD 2001 "level 1" category: herbaceous upland natural/semi-natural
vegetation (grassland) (% basin area, weighted by distance from sampling site)

pAGRIdw

Aggregated NLCD 2001 "level 1" category: crops and pasture (% basin area, weighted
by distance from sampling site)

pWETLDdw

Aggregated NLCD 2001 "level 1" category: wetlands (% basin area, weighted by
distance from sampling site)

Segment-scale land cover

SEGCUR

Segment length in meters. This is the curvilinear length of the stream upstream from the
sampling site

SEG_RSX

Number of road - stream intersections in segment area. Segment area is the riparian
zone (~100 m each side of stream centerline) along the segment

SEGRSXK

Number of road - stream intersections per stream segment kilometer

SEG_RMD

Mean distance from stream segment to nearest road (m). (mean distance of every point
along the stream - 30m pixels - to the nearest road to that point)

SINUOS

Segment sinuosity (unitless). Curvilinear length/ straight length between segment
end points

SEGGRAD

Segment gradient, m/km. Number of meters the stream falls in elevation for every
km of segment length

pWATRseg

Segment area in aggregated NLCD01 "level 1" category: water (% segment riparian
area)

pURBseg

Segment area in aggregated NLCD01 "level 1" category: developed (% segment riparian
area)

pBAREseg

Segment area in aggregated NLCD01 "level 1" category: barren (includes all level 2
barren and unconsolidated categories) (% segment riparian area)

pFORseg

Segment area in aggregated NLCD01 "level 1" category: forest (% segment riparian
area)

pRANGseg

Segment area in aggregated NLCD01 "level 1" category: shrubland (includes all level 2
shrub and scrub categories) (% segment riparian area)

pHERBseg

Segment area in aggregated NLCD01 "level 1" category: herbaceous upland
natural/semi-natural vegetation (grassland) (% segment riparian area)

pAGseg

Segment area in aggregated NLCD01 "level 1" category: crops and pasture (% segment
riparian area)

pWETseg

Segment area in aggregated NLCD01 "level 1" category: wetlands (% segment riparian
area)

Stream buffer land cover (~100 m each side of stream centerline)

P_NLCDB1

Aggregated NLCD 2001 "level 1" category: water (% buffer area)

P_NLCDB2

Aggregated NLCD 2001 "level 1" category: developed (% buffer area)

P_NLCDB3

Aggregated NLCD 2001 "level 1" category: barren (includes all level 2 barren and
unconsolidated categories) (% buffer area)

P_NLCDB4

Aggregated NLCD 2001 "level 1" category: forest (% buffer area)

P_NLCDB5

Aggregated NLCD 2001 "level 1" category: shrubland (includes all level 2 shrub and
scrub categories)(% buffer area)

P_NLCDB7

Aggregated NLCD 2001 "level 1" category: herbaceous upland natural/semi-natural
vegetation (grassland) (% buffer area)

P_NLCDB8

Aggregated NLCD 2001 "level 1" category: crops and pasture (% buffer area)

P_NLCDB9

Aggregated NLCD 2001 "level 1" category: wetlands (% buffer area)

NLCD_BIS

NLCD 2001 mean percent impervious surface in the riparian zone

Basin fragmentation

BSHAP_IX

Basin Shape Index (unitless). This is a measure of the basin shape/compactness.
Same metric as "SIM_" below, except calculated on the entire basin boundary, not
just particular patches within the basin. Values range from 1 to infinity. Low values
indicate compact shape (e.g., perfectly round basin would have value of 1.0), and
higher values indicate more irregular shapes (e.g., a very long skinny basin might
have a value of 3 or more)

NP_C1

Number of patches of water

PD_C1

Patch density (no./100 hectares) of water

LPI_C1

Largest Patch Index - Percentage of basin area composed of the largest patch of
water (%)

PAM_C1

Mean Patch Area - Mean patch area of water (ha)

SIM_C1

Shape Index Mean (unitless) for water. Measure of mean patch shape/compactness.
Values range from 1 to infinity. Low values indicate compact shape (e.g., perfectly
square patch would have value of 1), and higher values indicate more irregular
shapes (e.g., a very long skinny patch might have a value of 3 or more)

PIM_C1

Proximity Index for water, Mean - Measure of isolation and fragmentation of patches
(unitless). Large numbers mean many patches of the same type within the specified
proximity (in our case 1000m); low numbers the reverse

EDM_C1

Euclidean Nearest Neighbor Distance for water, Mean. Mean nearest neighbor
distance for patches of water (m). Measure of how dispersed the patches are

PLA_C1

Proportion of Like Adjacencies for water - Percentage of patch adjacencies that are of
the same type (%). If patches are surrounded by similar patches, this will be a high
number, if patches are mostly surrounded by a different kind of patch, it will be a
low number

NP_C2

Number of patches of developed land

PD_C2

Patch density (no./100 hectares) of developed land

LPI_C2

Largest Patch Index - Percentage of basin area composed of the largest patch of
developed land (%)

PAM_C2

Mean Patch Area - Mean patch area of developed land (ha)

SIM_C2

Shape Index Mean (unitless) for developed land. Measure of mean patch
shape/compactness. Values range from 1 to infinity. Low values
indicate compact shape (e.g., perfectly square patch would have value
of 1), and higher values indicate more irregular shapes (e.g. a very
long skinny patch might have a value of 3 or more)

PIM_C2

Proximity Index for developed land, Mean - Measure of isolation and
fragmentation of patches (unitless). Large numbers mean many
patches of the same type within the specified proximity (in our case
1000m); low numbers the reverse.

EDM_C2

Euclidean Nearest Neighbor Distance for developed land, Mean. Mean
nearest neighbor distance for patches of developed land (m). Measure
of how dispersed the patches are.

PLA_C2

Proportion of Like Adjacencies for Developed Land - Percentage of patch
adjacencies that are of the same type (%). If patches are surrounded
by similar patches, this will be a high number, if patches are mostly
surrounded by a different kind of patch, it will be a low number.

NP_C3

Number of patches of barren land

PD_C3

Patch density (no./100 hectares) of barren land

LPI_C3

Largest Patch Index - Percentage of basin area composed of the largest
patch of barren land (%)

PAM_C3

Mean Patch Area - Mean patch area of barren land (ha)

SIM_C3

Shape Index Mean (unitless) for barren land. Measure of mean patch
shape/compactness. Values range from 1 to infinity. Low values
indicate compact shape (e.g., perfectly square patch would have value
of 1), and higher values indicate more irregular shapes (e.g. a very
long skinny patch might have a value of 3 or more)

PIM_C3

Proximity Index for barren land, Mean - Measure of isolation and
fragmentation of patches (unitless). Large numbers mean many
patches of the same type within the specified proximity (in our case
1000m); low numbers the reverse.

EDM_C3

Euclidean Nearest Neighbor Distance for barren land, Mean. Mean nearest
neighbor distance for patches of barren land (m). Measure of how
dispersed the patches are.

PLA_C3

Proportion of Like Adjacencies for barren land - Percentage of patch
adjacencies that are of the same type (%). If patches are surrounded
by similar patches, this will be a high number, if patches are mostly
surrounded by a different kind of patch, it will be a low number.

NP_C4

Number of patches of forested land

PD_C4

Patch density (no./100 hectares) of forested land

LPI_C4

Largest Patch Index - Percentage of basin area composed of the largest
patch of forested land (%)

PAM_C4

Mean Patch Area - Mean patch area of forested land (ha)

SIM_C4

Shape Index Mean (unitless) for forested land. Measure of mean patch
shape/compactness. Values range from 1 to infinity. Low values
indicate compact shape (e.g., perfectly square patch would have value
of 1), and higher values indicate more irregular shapes (e.g., a very
long skinny patch might have a value of 3 or more)

PIM_C4

Proximity Index for forested land, Mean - Measure of isolation and
fragmentation of patches (unitless). Large numbers mean many
patches of the same type within the specified proximity (in our case
1000m); low numbers the reverse.

EDM_C4

Euclidean Nearest Neighbor Distance for forested land, Mean. Mean nearest
neighbor distance for patches of forested land (m). Measure of how
dispersed the patches are

PLA_C4

Proportion of Like Adjacencies for forested Land - Percentage of patch adjacencies
that are of the same type (%). If patches are surrounded by similar patches, this
will be a high number, if patches are mostly surrounded by a different kind of patch,
it will be a low number

NP_C5

Number of patches of shrub/grasslands

PD_C5

Patch density (no./100 hectares) of shrub/grasslands

LPI_C5

Largest Patch Index - Percentage of basin area composed of the largest patch of
shrub/grasslands (%)

PAM_C5

Mean Patch Area - Mean patch area of shrub/grasslands (ha)

SIM_C5

Shape Index Mean (unitless) for shrub/grasslands. Measure of mean patch
shape/compactness. Values range from 1 to infinity. Low values indicate compact
shape (e.g., perfectly square patch would have value of 1), and higher values
indicate more irregular shapes (e.g., a very long skinny patch might have a value
of 3 or more)

PIM_C5

Proximity Index for shrub/grasslands, Mean - Measure of isolation and fragmentation
of patches (unitless). Large numbers mean many patches of the same type within
the specified proximity (in our case 1000m); low numbers the reverse

EDM_C5

Euclidean Nearest Neighbor Distance for shrub/grasslands, Mean. Mean nearest
neighbor distance for patches of shrub/grasslands (m). Measure of how dispersed
the patches are

PLA_C5

Proportion of Like Adjacencies for shrub/grasslands - Percentage of patch adjacencies
that are of the same type (%). If patches are surrounded by similar patches, this will
be a high number, if patches are mostly surrounded by a different kind of patch, it
will be a low number

NP_C8

Number of patches of agricultural/pasture land

PD_C8

Patch density (no./100 hectares) of agricultural/pasture land

LPI_C8

Largest Patch Index - Percentage of basin area composed of the largest patch of
agricultural/pasture land (%)

PAM_C8

Mean Patch Area - Mean patch area of agricultural/pasture land (ha)

SIM_C8

Shape Index Mean (unitless) for agricultural/pasture land. Measure of mean patch
shape/compactness. Values range from 1 to infinity. Low values indicate compact
shape (e.g. perfectly square patch would have value of 1), and higher values
indicate more irregular shapes (e.g., a very long skinny patch might have a value
of 3 or more)

PIM_C8

Proximity Index for agricultural/pasture land, Mean - Measure of isolation and
fragmentation of patches (unitless). Large numbers mean many patches of the
same type within the specified proximity (in our case 1000m); low numbers the
reverse

EDM_C8

Euclidean Nearest Neighbor Distance for agricultural/pasture land, Mean. Mean
nearest neighbor distance for patches of agricultural/pasture land (m). Measure
of how dispersed the patches are

PLA_C8

Proportion of Like Adjacencies for agricultural/pasture land - Percentage of patch
adjacencies that are of the same type (%). If patches are surrounded by similar
patches, this will be a high number, if patches are mostly surrounded by a different
kind of patch, it will be a low number

NP_C9

Number of patches of wetlands

PD_C9

Patch density (no./100 hectares) of wetlands

LPI_C9

Largest Patch Index - Percentage of basin area composed of the largest patch of
wetlands (%)

PAM_C9

Mean Patch Area - Mean patch area of wetlands (ha)

SIM_C9

Shape Index Mean (unitless) for wetlands. Measure of mean patch shape/compactness.
Values range from 1 to infinity. Low values indicate compact
shape (e.g. perfectly square patch would have value of 1), and higher values
indicate more irregular shapes (e.g., a very long skinny patch might have a value
of 3 or more)

PIM_C9

Proximity Index for wetlands, Mean - Measure of isolation and fragmentation of
patches (unitless). Large numbers mean many patches of the same type within
the specified proximity (in our case 1000m); low numbers the reverse.

EDM_C9

Euclidean Nearest Neighbor Distance for wetlands, Mean. Mean nearest neighbor
distance for patches of wetlands (m). Measure of how dispersed the patches are

PLA_C9

Proportion of Like Adjacencies for wetlands - Percentage of patch adjacencies that
are of the same type (%). If patches are surrounded by similar patches, this will be a
high number, if patches are mostly surrounded by a different kind of patch, it will be a low number

Antecedent land cover: land cover in candidate basins with urban intensity (MA-NUII) ≤ 10

AFOR

Antecedent forest land (P_NLCD_4)

AAG

Antecedent agriculture, % row crop and grasslands (P_NLCD_7 +  P_NLCD_8)

TABLE B2. Infrastructure variables.

Variable

Definition

RDLENGTH

Length of TIGER roads in watershed (km). Has been adjusted to exclude non-paved or access
roads, bike paths, etc.

ROADDEN

Road density in watershed = km of road/sq km of basin drainage area

RDARDEN

Road area index density. Road length multiplied by an area factor (by type of road) normalized
by watershed area (km/km²)

RDTRDEN

Road traffic index density. Road length multiplied by a traffic factor (by type of road) normalized
by watershed area (km/km²)

PSCOUNT

Density (no./100 km²) of point source dischargers in watershed (EPA database - NPDES)

TRICOUNT

Density (no./100 km²) of Toxics Release Inventory sites in watershed

TABLE B3. Census variables.

Variable

Definition

POP2000

2000 population (2000 census block based)

POPDEN00

2000 population density (people/square km) (2000 census block based)

HHDEN

Household density (occupied housing units per square kilometer) (2000 census block-group
based)

PPURBAN

Proportion of population living in urban area (2000 census block-group based)

PHO_G4P

Proportion of households occupied by 4 or more people (2000 census block-group based)

PP_L5Y

Proportion of population less than 5 years old (2000 census block-group based)

PP_SH95

Percent of population living in same house as in 1995 (2000 census block-group based)

PHS_G25

Proportion of population greater than 25 years old that have High School degrees (2000 census
block-group based)

PBCH_G25

Proportion of population greater than 25 years old that have Bachelors degree (2000 census
block-group based)

PHHI_L10

Proportion of households with income less than $10,000, 2000 (2000 census block-group based)

PHHI_L20

Proportion of households with household income less than $20,000 per year (2000 census block-
group based)

PHHI_L30

Proportion of households with income less than $30,000, 2000 (2000 census block-group based)

P_OWN

Proportion of occupied housing units that are owner occupied, 2000 (%), (2000 census block-
group based)

PHU_L5

Proportion of housing units built between 1995–2000 (2000 census block-group based)

PHU_L10

Proportion of housing units built between 1990–2000 (2000 census block-group based)

PHU_L20

Proportion of housing units built between 1980–2000 (2000 census block-group based)

PHUT

Percent of occupied housing units using utility gas (natural gas) as fuel (2000 census
block-group based)

PHLP

Percent of occupied housing units using liquid petroleum gas as fuel (2000 census
block-group based)

PHEL

Proportion of occupied housing units using electricity as fuel (2000 census block-group based)

MEDHHI

Median household income, 2000 (dollars) (2000 census block-group based)

PHOIL

Percent of occupied housing units using oil as fuel (2000 census block-group based)

PHWOOD

Percent of occupied housing units using wood as fuel (2000 census block-group based)

HUDEN

Density of housing units (housing units/square kilometer) (2000 census block-group based)

POCC_G65

Proportion of housing units occupied by persons greater than 65 years of age (2000 census
block-group based)

PPRURAL

Proportion of population living in rural area (2000 census block-group based)

PPMALE

Proportion of population that is male (2000 census block-group based)

PPFEMALE

Proportion of population that is female (2000 census block-group based)

PHFAM

Proportion of households occupied by a family (2000 census block-group based)

PHNONFAM

Proportion of households occupied by a non-family (2000 census block-group based)

PHO_L3P

Proportion of households occupied by less than 3 people (2000 census block-group based)

P_US

Proportion of citizens born in US (2000 census block-group based)

P_INSTAT

Proportion of citizens born in State of Residence (2000 census block- group based)

P_OUTST

Proportion of citizens born in other States in the US (2000 census block-group based)

P_NONUS

Proportion of citizens not born in US (2000 census block-group based)

PC_CTY95

Proportion of citizens living in same county more than 5 years (since 1995) (2000
census block-group based)

PC_ST95

Proportion of citizens living in same State more than 5 years (since 1995) (2000
census block-group based)

PM_GT25Y

Proportion of male population greater than 25 years of age (2000 census block-group based)

PF_GT25Y

Proportion of female population greater than 25 years of age (2000 census block-group based)

PM_GT16E

Proportion of male population greater than 16 years of age that are employed (2000
census block-group based)

PF_GT16E

Proportion of female population greater than 16 years of age that are employed (2000
census block-group based)

PPOP_POV

Proportion of population with income below the poverty level (2000 census block-group based)

PFAM_POV

Proportion of families with income below the poverty level (2000 census block-group based)

PHH_POV

Proportion of households with income below the poverty level (2000 census block-group based)

P_OCCUPY

Proportion of housing units that are occupied (2000 census block-group based)

P_VACANT

Proportion of housing units that are vacant (2000 census block-group based)

P_RENT

Proportion of occupied housing units that are renter occupied, 2000 (%), (2000 census
block-group based)

PH_1PERS

Proportion of households occupied by 1 person (2000 census block-group based)

PH_2PERS

Proportion of households occupied by 2 persons (2000 census block-group based)

PH_3PERS

Proportion of households occupied by 3 persons (2000 census block-group based)

PH_4PERS

Proportion of households occupied by 4 persons (2000 census block-group based)

PH_5PERS

Proportion of households occupied by 5 persons (2000 census block-group based)

PH_6PERS

Proportion of households occupied by 6 persons (2000 census block-group based)

PH_7PERS

Proportion of households occupied by 7 or more persons (2000 census block-group based)

PHU_G20

Proportion of housing units built prior to 1979 (1939 or earlier to 1979) (2000 census
block-group based)

PHU_G30

Proportion of housing units built prior to 1969 (1939 or earlier to 1969) (2000 census
block-group based)

PHU_G40

Proportion of housing units built prior to 1959 (1939 or earlier to 1959) (2000 census
block-group based)

PHU_G50

Proportion of housing units built prior to 1949 (1939 or earlier to 1949) (2000 census
block-group based)

PHU_G60

Proportion of housing units built prior to 1939 (2000 census block-group based)

PERCAPIN

Per Capita income (2000 census block-group based)

MFAMINC

Median family household income (2000 census block-group based)

MNFAMINC

Median non-family household income (2000 census block-group based)

POP90_00

Proportional change in population from 1990–2000 (2000 census block based)