Estimating Riparian Area Extent and Land Use

in the Midwest

Many different types of riparian areas can be found throughout the seven-State Midwest Region. 
1

The ecological and social importance of riparian areas as landscape elements is undisputed (e.g., see Verry

et al. 2000); however, there is great uncertainty about the cumulative importance of riparian areas in many

landscapes and regions. This is a consequence of inadequate inventory data on the extent, type, and land

use/land cover of riparian resources. The seven-State Midwest Region of the continental United States is no

exception (figure 1). This region is one of the most water-rich areas in the continental United States, yet we

are not aware of any general accounting of amount, type, or land use of riparian resources here.

Because of the lack of regional data on riparian resources, it is difficult to determine the degree to which

different types of riparian areas receive protection, the extent of change in riparian land use/land cover over

time, and the social and economic benefits derived from different types of riparian land use. At issue is the

availability and adequacy of riparian resource information used to make policy and management decisions

in the region.

Figure 1.—The seven-State

Midwest Region.

Introduction
2

A fundamental barrier to adequate assessment of riparian resources is uncertainty over appropriate

definitions. We define a riparian area as an ecotone of functional interaction between land and surface water.

More specifically, it is that land area that directly influences surface waters and, in turn, is directly

influenced by them (figure 2; Ilhardt et al. 2000). Under this definition, riparian areas include lands

associated with all types of surface waters including lakes, open-water wetlands, rivers, and streams (six

different photographic examples of riparian areas are included throughout this report). In other words,

riparian areas are not exclusively floodplains, or wetlands, or near-bank environments, nor are they

associated only with streams and rivers. Unfortunately, many people continue to view riparian areas under a

restricted definition (i.e., streamside forest and floodplains), introducing the potential for gross

underestimation of riparian area extent in regional landscapes.

Floodplain

Figure 2.—Stylized

representation of a 

riparian area showing 

the lateral extent 

of various ecological

interactions between 

land and water.
Method of riparian delineation is another factor that influences estimates of riparian resources in a region.

Fixed-width approaches for delineation, e.g., 1-pixel buffers (30 m) on Landsat imagery, are common and

relatively straightforward to apply (e.g., Hanowski et al. 2000). However, fixed-width approaches are

tenuous because they have no functional relationship to the actual riparian areas on the ground, which vary

naturally in width among and within systems (Palik et al. 2000). We believe there is a need to explore the

range of variation in riparian extent introduced using different definitions of riparian areas and delineation

approaches (e.g., fixed-width approaches, functional approaches, hydric soil-based approaches).

In this report, we quantify the amount of riparian area in the seven-State Midwest Region of the

continental United States. Our objective is to assess the physical extent of riparian areas associated with

different types of water bodies, i.e., stream, river, lake, and wetland, and to estimate total extent of riparian

lands in the region. Additionally, we characterize land use/land cover, e.g., residential, industrial,

agriculture, forests, of riparian areas in each State and for the region as a whole. In this assessment, we

determine (1) how much of the regional landscape is riparian, (2) how delineation method influences

riparian estimates, and (3) how people have altered the characteristics of riparian areas in the region.

3
4

Amount of Riparian Area

We included seven States in the Midwest Region of

the continental United States in this analysis

(Minnesota, Wisconsin, Iowa, Missouri, Illinois,

Indiana, and Michigan). For each State, we

assembled 1:100,000 USGS digital line graph

(DLG) hydrography data layers on streams, lakes,

and wetlands. Hydrography data sets were

accessed through each State’s geographic data

clearinghouse Web site. Each State, however, has

modified the DLG after field rectifications. Digital

data for streams, lakes, and wetlands were not

available for all States. Lake data were not available

for Illinois, Iowa, and Indiana. Wetland data were

not available for Illinois, Iowa, and Missouri (see

section on Caveats and Limitations). Great Lakes

shorelines were excluded from our analysis, as

were ditches and canals.

We assessed riparian area extent using several

different delineation approaches. First, we

delineated fixed-width buffers adjacent to all

streams, lakes, and wetlands found on the

hydrography layers. We delineated both 30-m and

60-m buffers using the BUFFER command within

ArcInfo 8.0. From these numbers, we estimated

percent of area for each State that is riparian, based

on total land area of a State, exclusive of water and

wetlands (i.e., upland land area only).

Secondly, we delineated riparian areas using soil

characteristics derived from 1:250,000 STASGO

data (State Soil Geographic Database;

(http://www.ftw.ncrs.usda.gov/stst_data.html). Our

intent was to assess riparian extent using criteria

that would consider only floodplains, wetlands,

and frequently flooded settings, i.e., a restricted

definition of a riparian area. For this analysis, we

assumed a land area was riparian if it met four

criteria: 

(1) the soil belonged to hydrologic groups 

C or D (slow infiltration, impeding or

impervious layers, fine texture), or

combinations of C or D and other

hydrologic groups (A/D, B/D, C/D) 

(table 1); 

(2) the soil was classified as hydric; 

Approach
(3) the annual flood frequency was frequent

(>50 percent probability of an annual

flood) or occasional (5-50 percent

probability of an annual flood); and 

(4) the drainage class was poorly drained (P),

very poorly drained (VP), or a

combination of poorly drained/somewhat

poorly drained (P/SP), or poorly

drained/very poorly drained (P/VP)

(table 2).

Finally, we estimated riparian extent using a

method based on potential for infrequent, but

potentially significant interactions between land

and water through large magnitude flooding. For

this approach, we used the Federal Emergency

Management Agency’s (FEMA) flood frequency

digital data (http://www.fema.gov/mit/tsd/) to

determine amount of land area affected by 

100-year floods. These data were available in

digital format statewide only for Illinois.

5

Northern hardwoods 

adjacent to a 

headwater stream.
6

Table 1.—Hydrologic classes in the STATSGO database

Hydrology class Characteristics

A High infiltration rates. Soils are deep, well drained to

excessively drained sands and gravels.

B Moderate infiltration rates. Deep and moderately deep.

Moderately well and well drained soils with moderately 

coarse textures.

C Slow infiltration rates. Soils with layers impeding 

downward movement of water, or soils with moderately 

fine or fine textures.

D Very slow infiltration rates. Soils are clayey, have a high 

water table, or are shallow to an impervious layer.

A/D Drained/undrained hydrology class of soils that can be 

drained and are classified.

B/D Drained/undrained hydrology class of soils that can be 

drained and are classified.

C/D Drained/undrained hydrology class of soils that can be 

drained and classified.
7

Soil drainage class Characteristics

Excessively drained (E) Soils have very high and high hydraulic conductivity 

and low water holding capacity. Depth to water table is 

more than 6 feet.

Well drained (W) Soils have intermediate water holding capacity. Depth to

water table is more than 6 feet.

Moderately well Soils have a layer of low hydraulic conductivity, wet state 

high in the profile. Depth to water table is 3 to 6 feet.

Poorly drained (P) Soils may have a saturated zone, a layer of low hydraulic

conductivity, or seepage. Depth to water table is less

than 1 foot.

Somewhat excessively Soils have a high hydraulic conductivity and low water

holding capacity. Depth to water table is more than 6 feet.

Somewhat poorly Soils commonly have a layer with low hydraulic conductivity,

wet state high in profile. Depth to water table is 1 to 3 feet.

Very poorly drained (VP) Soils are wet to the surface most of the time. Depth to

water table is less than 1 foot, or is ponded.

Table 2.—Soil drainage classes in the STATSGO database

drained (SE)

drained (SP)

drained (MW)
8

Riparian Land Use

Land use of riparian areas, delineated with 30-m

and 60-m buffers, was determined using National

Land Cover Data (http://landcover.usgs.gov) for

each State. Land cover data are based on 30-m

Landsat thematic mapper imagery. There are 

19 land cover classes in this classification. We

grouped these classes into four broad categories

including developed (urban), agricultural,

natural/semi-natural, and other (transitional) 

(table 3). Land cover data were intersected with

riparian areas using LATTICECLIP within ArcGrid

(ESRI 1999). The percentage of each land cover

class found within delineated riparian areas was

summarized for the region and by State and

hydrologic type (lake, stream, wetland).

A. Developed

1. Low Intensity Residential

2. High Intensity Residential

3. Commercial/Industrial/Transportation

4. Quarries/Strip Mines/Gravel Pits

5. Urban/Recreational Grasses 

B. Natural/Semi-natural

6. Deciduous Forest

7. Evergreen Forest

8. Mixed Forest

9. Grasslands/Herbaceous

10. Shrubland

11. Bare Rock/Sand/Clay

12. Woody Wetlands

13. Emergent Herbaceous Wetlands

C. Agriculture

14. Orchards/Vineyards/Other 

15. Pasture/Hay

16. Row Crops

17. Small Grains

18. Fallow

D. Other

19. Transitional

Table 3.—Land cover class from the National Land Cover database used in this analysis
A number of caveat and limitations associated with

our data and procedures may influence estimates,

restrict accuracy, and argue for caution in

interpretation of the results. First, complete

hydrologic data were not available for each State.

Specifically, we lacked digital lake data for Illinois,

Iowa, and Indiana and wetland data for Illinois,

Iowa, and Missouri. These omissions resulted in an

underestimate of riparian resources for these

States. Fortunately, wetlands and lakes are of

relatively lesser geographic importance in these

States, compared to the northern Lake States of

Michigan, Wisconsin, and Minnesota (figure 3). As

such, omission of lake and wetland data for these

States may not grossly underestimate total extent

of riparian area in the region. Second, there is

inconsistency in the extent to which intermittent

streams are accounted for in each State. Michigan,

Wisconsin, and Minnesota stream layers include

intermittent streams, either separately or included

with perennial streams. We were unable to

determine whether intermittent streams are

included in the stream hydrography layer for

Illinois, Missouri, Iowa, and Indiana. As such, it is

possible that riparian areas for the latter States are

underestimated. Moreover, intermittent streams are

notoriously underrepresented on USGS quad maps

because of the difficulty in interpreting these 

systems on air photography, particularly in forest

settings. As such, stream hydrolayers for all States,

even those that specifically identify intermittent

channels, likely grossly underestimate these

systems. All of the above caveats likely result in an

underestimate of total riparian resources in each

State and the region as a whole. On the other

hand, overlap in riparian buffers among stream,

river, and wetland riparian coverages can

potentially inflate estimates of riparian area in

some States. We did not determine how much

overlap occurred, but it likely is only an issue in

States where both streams and large wetlands are

extensive, including

Minnesota, Michigan, and

Wisconsin. Finally, our

wetland data layers were

not restricted to openwater wetlands, as in some

assessments (Minnesota

Department of Natural

Resources 2001). We also

included marshes,

swamps, and bogs. As

such, our estimates of

riparian area around

wetlands will be higher

than estimates that are

restricted to open-water

wetlands.

9

Shown above is a black ash

forest along a small stream.

Caveats and Limitations
10

Figure 3.—Area of surface

water (blue bars) and

wetlands (red bars), in

thousands of hectares, 

for each State in the

Midwest Region. 

Source: 1997 U.S.

Department of Agriculture

Natural Resource

Conservation Service,

National Forest Inventory

(www.nrcs.usda.gov).

Wetland area includes only

wetlands and deepwater

habitats on non-Federal land.
A Fixed-Width Buffer Approach

We estimate that riparian areas cover at least 8.9

million hectares (based on 30-m buffers) to 13.2

million hectares (60-m buffer) in the seven States,

or approximately 8.5 to 12.6 percent of total land

area in the region (figure 4). The estimate does not

double from 30-m to 60-m buffers because of

increased overlap between adjacent water bodies as

buffer width increases.

Amount of riparian area varies widely among

States, ranging from 4.7 million hectares in

Minnesota to 0.3 million hectares in Iowa (based

on a 60-m buffer; figure 5). Approximately 77

percent of the regional total occurs in Minnesota,

Wisconsin, and Michigan (figure 6). We estimate

that up to 17 to 23 percent (based on a 60-m

buffer) of the land base in these States is riparian,

compared to 2 to 20 percent in Missouri, Iowa,

Indiana, and Illinois (figure 7). Estimates of

riparian land areas for some States (MN, WI, MI,

IN) do not double between 30-m and 60-m

buffers; these States included wetland data layers.

States that lacked wetland data (IL, MO, IA) had

approximately double the land area in 60-m

riparian buffers as in 30-m buffers. This indicates

that overlap among adjacent wetlands, as buffer

width increases, largely drives the nonlinear

relationship between buffer width and riparian

land area at the regional scale.

Our assessment of riparian extent in the region

must be interpreted with caution, because we rely

on data and procedural assumptions that decrease

accuracy or alter estimates, relative to other

assessments. Two assumptions likely lead to an

underestimate of total riparian resources in some

States and in the region, while a third likely

overestimates riparian resources in some States.

The lack of digital hydrologic data on wetlands

and lakes for some States (see Approach) and the

generally poor inventories of intermittent streams

in most States result in underestimates of total

riparian area in individual States and the region.

Conversely, an undetermined amount of overlap

among data layers, particularly stream and wetland

data layers in States where both of these resources

are abundant, may inflate the total extent of

riparian area for these States and the region.

Finally, our estimates of amount of riparian area for

individual States may differ from other assessments

due to differences in scale of data layers,

definitions of land area, and types of water bodies

and wetlands included in the survey. For example,

using a 60-m buffer, others have estimated the

total amount of riparian area in Minnesota at 3.1

million hectares (Minnesota Department of Natural

Resources 2001), 34 percent below our estimate of

4.7 million hectares for the State. The difference is

likely due to wetland types in our definition, not

just open-water wetlands, as in the other survey.

11

Amount of Riparian Area in the Midwest Region

...our estimates of amount of riparian

area for individual States may differ from

other assessments due to differences in scale of

data layers, definitions of land area, and types of

water bodies and wetlands included in the survey.
12

Figure 4.—Cumulative land

area and cumulative riparian

area, based on 30-m and 

60-m buffers, respectively,

for the Midwest Region.

Figure 5.—Total land area

(blue bars) and riparian 

land area, based on

30-m (red bars) and 

60-m (yellow bars) buffers, 

for each State in the 

Midwest Region. Values are

thousands of hectares.
13

Figure 6.—Percent

contribution by State to 

total riparian area in the

Midwest Region based 

on 30-m (blue bars) 

and 60-m (red bars) 

buffers, respectively.

Figure 7.—Percent riparian

area by State in the

Midwest Region. Blue 

slices represent percent 

of total land area that is

riparian in a State, based 

on 60-m buffer around all

water bodies.
14

Alternative Delineation: Hydric

Soil and Flood Probability

Indicators

We sought to contrast estimates of riparian area

extent based on fixed-width buffers with alternative

approaches to delineation, including one that was

more restrictive (i.e., equating riparian areas with

wetlands and floodplains) and one that was

functionally based (e.g., land area influenced by

infrequent, ecosystem-altering floods). The

alternative approaches we used included (1)

riparian delineation using hydric soil indicators

and (2) delineation based on 100-year flood

probability data. Both were derived from readily

available, although not geographically complete,

digital data sources. Estimates based on these

approaches are provided simply as points of

comparison with the buffer-based approach. We

make no claims as to their accuracy in reflecting

actual riparian extent.

Assessment of riparian area based on hydric soil

characteristics generally differs greatly from results

based on the fixed-width buffer analysis (table 4).

For three States (MN, WI, IN), the restrictive

delineation underestimates the amount of riparian

area by an order of magnitude, compared to 30-m

or 60-m fixed-width buffers. Conversely, for Iowa,

this approach increases the riparian estimate by an

order of magnitude (table 4), perhaps because the

buffer analysis omitted wetland data for this State,

while the soil-based approach included wetlands

by definition. For Missouri, riparian area estimates

based on hydric soil conditions and the 60-m

buffer were nearly identical, while the soil estimate

for Illinois fell midway between the 30-m and 

60-m buffer estimates (table 4).

Probability data for 100-year floods were available

statewide in digital format only for Illinois. Our

estimate of riparian area using this approach

reflects a longer term perspective to land-water

interactions. This longer term perspective is not

without precedent. Research in other regions has

demonstrated that infrequent, large magnitude

floods can have important ecosystem-altering

effects outside of a floodplain, including extensive

vegetation mortality (Michener et al. 1998, Palik

1999). Using these data, we estimated Illinois

riparian area at nearly 1.6 million hectares,

substantially higher than either soil or buffer

estimates (table 4).

Open-water wetland 

in an urbanized area.
15

State Soil 30-m buffer 60-m buffer FEMA flood rating2

Minnesota 429,807 3,424,776 4,677,041

Iowa 1,193,446 173,154 342,825

Illinois 497,655 329,082 619,940 1,583,303

Wisconsin 265,374 1,602,854 2,462,914

Indiana 314,009 1,188,386 1,864,936

Missouri 729,121 378,821 736,338

Michigan 11,796,911 2,531,346

1

Soil data incomplete for Michigan.

2

Available only for Illinois.

Table 4.—Riparian area (hectares) based on soil characteristics, fixed-width buffers, and flood indicators
16

Regionally, about 48 percent of total riparian lands

(based on the mean of 30-m and 60-m buffers) are

associated with wetlands, while 36 percent are

associated with streams and rivers and 16 percent

with lakes (table 5). But the results must be

interpreted with caution, because several States 

(IL, IA, IN, MO) did not have lake or wetland

hydrology data available. Consequently, stream

riparian areas in these States are overrepresented as

a percent of total riparian area. On the other hand,

wetlands and lakes in these States are much less

extensive than in the northern Lake States (MI, WI,

MN; figure 3). Consequently, the lack of

accounting for wetlands or lakes in some States

may not overly bias our regional results. Moreover,

a full accounting of wetlands in all States would

only serve to emphasize that most riparian areas in

the region are associated wetlands, rather than

streams and rivers.

Types of Riparian Areas in the Midwest Region

30-m buffer 60-m buffer

State Stream Wetland Lake Stream Wetland Lake

Minnesota 601,543 2,646,383 176,850 1,401,850 2,928,551 346,640

Iowa 173,154 na na 342,825 na na

Illinois 329,082 na na 619,940 na na

Wisconsin 425,979 11,176,876 1,062,882 1 1,400,032

Indiana 277,336 911,050 na 557,613 1,307,323 na

Missouri 318,945 na 59,875 641,624 na 94,714

Michigan 494,400 1,232,540 69,971 988,800 1,409,641 132,904

Total 2,620,439 4,789,973 1,483,572 5,615,534 5,646,515 1,974,291

Percent 29.5 53.9 16.7 42.4 42.7 14.9

1

Lake and wetland data combined for Wisconsin.

Table 5.—Riparian area (hectares) by type in the seven midwestern States based on 30-m and 60-m buffers
17

Land Use of Riparian Areas in the Midwest Region

Riparian lands in the Midwest support 18 of 19

possible land cover classes (table 6). According to

our analysis, fallow lands were nonexistent in

riparian areas of the region and thus are not

included in the agricultural category. We grouped

17 classes into three broad categories including

developed, natural/semi-natural, and agriculture

(table 6). The 18th class, transitional land cover,

was rare in the region (table 6) and was excluded

from further consideration.

Based on our groupings, approximately 72 percent

of midwestern riparian areas support natural or

semi-natural land cover, including forest, emergent

wetland vegetation, natural grassland, or shrubland

(figure 8). Within the natural/semi-natural

grouping, forest (deciduous, evergreen, mixed, and

woody wetland) is the predominant land cover in

all States. Another 26 percent of riparian area in

the region has been converted to agriculture, while

1.4 percent has been converted to developed

(urban/suburban) land uses (figure 8).

There is large variation in riparian land cover

among the seven midwestern States (table 6, figure

9). The northern Lake States (MN, WI, MI) contain

the greatest amounts of natural/semi-natural

riparian areas (73-81 percent, based on 60-m

buffers), compared to the Farm Belt States (IA, IN,

IL, MO; 38-55 percent). Conversely, the latter

States have a much higher percentage of

agricultural conversion of riparian areas (43-58

percent), compared to Minnesota, Wisconsin, and

Michigan (18-26 percent).

Developed land cover in riparian areas is higher in

the Farm Belt States (2-4 percent) than the

northern Lake States (1 percent), but still low

overall (table 6, figure 9). Even Illinois, arguably

the most urbanized State in the region, has only 

3 percent of riparian lands in the developed class

(figure 9).

Data interpretation and definitions will affect

estimates of riparian land use within individual

States. Again, using Minnesota as our example, we

found much less agricultural conversion in riparian

areas (20 percent, based on a 60-m buffer) than in

a similar assessment (50 percent; Minnesota

Department of Natural Resources 2001).

Conversely, we found much more woody wetland

vegetation (45 percent) in riparian buffers than did

the earlier assessment (11 percent). Our inclusion

of all wetland types, not just open-water wetlands,

likely accounts for these differences. Not only did

our estimate include a greater amount of riparian

area associated with wetlands, but also swamps,

marshes, and bogs are more likely to be associated

with wetland forest around their periphery than

with agricultural land.

...approximately 72 percent of 

midwestern riparian areas support natural 

or semi-natural land cover, including forest, 

emergent wetland vegetation, natural grassland, 

or shrubland.
18

State

Land use Minnesota Iowa Illinois

Buffer width Buffer width Buffer width

30-m 60-m 30-m 60-m 30-m 60-m

Developed

Low Intensity Residential 4,028 9,681 980 2,037 3,619 7,096

High Intensity Residential 1,261 2,776 169 386 1,150 2,405

Commercial/Industrial/ 7,718 15,151 4,203 7,219 2,807 5,345

Quarries/Strip Mines/Gravel Pits 2,926 4,545 108 213 400 691

Urban/Recreational Grasses 2,299 4,950 310 771 2,992 6,016

Natural/Semi-natural

Deciduous Forest 315,589 548,262 49,061 86,762 82,253 154,340

Evergreen Forest 103,099 158,642 217 381 6,925 10,863

Mixed Forest 100,839 166,127 529 973 3,876 6,766

Grasslands/Herbaceaous 711 1,191 6,585 13,555 3,577 6,989

Shrubland 23,456 30,885 0 0 51 94

Bare Rock/Sand/Clay 69 172 813 1,028 313 540

Woody Wetlands 1,882,200 2,112,904 22,575 37,536 64,536 104,339

Emergent Herbaceaous Wetlands 559,805 694,038 7,588 12,182 13,084 17,187

Agriculture

Orchards/Vineyards/Other 0 0 0 0 6 15

Pasture/Hay 154,479 307,327 25,935 54,669 60,109 121,996

Row Crops 238,578 572,474 52,995 122,551 82,879 174,013

Small Grains 17,211 32,996 1,086 2,561 501 1,235

Other

Transitional 10,507 14,921 0 0 3 10

Table 6.—Riparian area (hectares) of the seven midwestern States in different land use/land cover classes

See table 3 for complete land cover descriptors

Transportation
19

State

Wisconsin Indiana Missouri Michigan

Buffer width Buffer width Buffer width Buffer width

30-m 60-m 30-m 60-m 30-m 60-m 30-m 60-m

3,192 8,110 17,496 27,972 1,677 3,366 7,174 14,711

1,005 2,521 2,766 4,319 371 737 1,894 3,770

4,006 9,135 10,714 16,309 2,469 4,516 5,352 9,905

282 480 2,064 3,724 255 481 2,221 4,632

2,163 4,947 6,112 10,027 1,415 2,973 2,321 4,632

421,314 690,341 287,723 433,148 112,489 213,134 280,430 458,508

51,088 82,904 17,338 27,851 12,111 21,330 90,017 133,186

101,687 158,848 6,665 8,635 15,008 27,638 65,777 105,260

15,100 22,497 7,101 11,411 5,285 11,101 14,802 22,555

70 85 104 186 277 604 114 178

457 558 239 419 1,180 1,753 213 328

507,233 611,703 123,276 141,142 72,754 117,073 902,276 1,112,234

203,252 233,438 22,946 26,085 11,830 18,177 185,340 219,325

14 14 0 0 0 0 1 1

116,614 272,100 150,743 305,352 58,664 132,810 49,910 92,833

173,052 361,760 350,594 670,783 78,784 171,107 187,006 348,028

25 102 178 347 4,163 9,347 44 93

2,301 3,372 1,700 2,916 89 191 2,019 3,078
20

0

2,000

4,000

6,000

8,000

10,000

Figure 8.—Riparian land 

use in the Midwest Region

based on 30-m and 60-m

buffers. Percentages are 

portions of total riparian

area in the region.

Figure 9.—Riparian land

use in the Midwest Region.

Colors represent

percentages of riparian

lands in different land cover

categories (red is

agriculture, yellow is 

natural land cover, 

blue is urban/developed).
21

Amount of Riparian Area

Our estimates of riparian land area for several of

the midwestern States, and consequently the region

as a whole, are conservative due to data limitations.

Nonetheless, the magnitude of the estimates point

to substantial ecological, social, and economic

importance of riparian resources in the region,

particularly for the upper Great Lake States of

Minnesota, Wisconsin, and Michigan.

Several potential implications are suggested by

these data. For example, policies that result in

restricted land use for forestry or agriculture within

riparian areas could have significant negative

impacts on local and regional economies. For

instance, Minnesota contains 6.1 million hectares

of productive forest land (Shifley and Sullivan

2002), of which 23 percent, or1.4 million hectares,

potentially is riparian. Restrictive or no-harvest

policies for 1.4 million hectares of productive

riparian forests would have measurable negative

economic consequences for the State. Conversely,

the cumulative importance of riparian resources in

Minnesota and the region as a whole suggests that

policies and practices that significantly degrade

riparian habitat will have broad negative impacts

on wildlife populations, water quality, and biotic

diversity. Understanding multidimensional

ecological and economic responses to different

amounts and types of riparian protection is an

important policy need.

Our analysis demonstrates how a riparian

delineation approach might influence policy and

management decisionmaking. An example of this is

the nonlinear relationship between riparian buffer

width and amount of riparian land area. For the

region as a whole, doubling riparian buffer width

from 30 m to 60 m results in only a 49-percent

increase in riparian land area. This same

nonlinearity is evident for all States that include

wetland data layers (MN, WI, MI, IN). One policy

interpretation of this is that doubling riparian

management buffer widths throughout a State or

region, while presumably resulting in greater

ecological protection of aquatic ecosystems and

water quality, will not double the amount of land

area potentially falling into use-restricted riparian

management area designations. The shape of the

response function between riparian management

buffer width and ecological function needs better

clarification before the economic and social

consequences of riparian area delineation can be

fully appreciated.

Implications and Needs
22

Types of Riparian Areas

At the regional scale, the majority of midwestern

riparian land area is associated with wetlands. This

is an important result because most people equate

riparian areas strictly with stream ecosystems.

Clearly, this is not the case for much of the region.

Similarly, lake riparian areas, although not as

extensive as those associated with streams or

wetlands, are a significant resource in the region.

The role that lake and wetland riparian

management zones have in protecting ecological

functions in associated water bodies is greatly

understudied relative to streams.

The generally poor accounting of intermittent

channels in hydrologic data layers for the Midwest

likely leads to large, but underdetermined,

underestimates of the amount of total and streamassociated riparian land area. Spatial data on

intermittent streams are notoriously incomplete,

because of difficulty in identifying small streams

using air photography. With better inventory, it is

likely that the amount of stream riparian areas

would increase, perhaps even exceeding that

associated with wetlands in some States.

A bottomland hardwood forest along a river.
23

Riparian Land Use

On the surface, the large amount of riparian land

area in natural/semi-natural land cover classes

suggests that riparian functions, including

sediment filtering, carbon storage, and wildlife

habitat, are being maintained in the region.

Although this is an encouraging result, it must be

interpreted with caution. Natural land cover classes

impart only limited information about ecosystem

structure and function. They say nothing about

vegetation age, species composition, or local

disturbances that can degrade riparian

functionality. Moreover, our assessment of riparian

land use/land cover, based on the fixed-width

buffer approach, is limited to at the most first 60 m

of land around or adjacent to lakes, wetlands, and

streams. Protection of water quality and aquatic

habitat is equally dependent on land use and cover

in the larger watersheds outside of the riparian

area. Our assessment does not account for

condition in the watershed proper.

The regional extent of land cover conversion in

riparian areas to agricultural or other development

is likely underestimated because of poor

documentation of intermittent streams. For

example, in Michigan, 61 percent of riparian areas

associated with documented intermittent streams

have been converted to agriculture, or are in

developed urban areas, compared to 19 percent of

riparian areas in the State as a whole. Better

inventory and accounting of intermittent streams in

the region would likely increase the estimate of

riparian land that is in agriculture or otherwise

developed. Advanced remote sensing

methodologies are needed to better document

intermittent and small perennial stream locations

and associated land use/land cover.

Sedge meadow along a small stream.
24

1. Cumulatively, riparian areas occupy up to 13

percent of the land base in the seven-State

Midwest Region. 

2. Riparian area, as a percent of total land area,

exceeds 17 percent in four midwestern States

(MN, WI, MI, IN).

3. Amount of riparian area is likely

underestimated in each State and the region

due to limitations of available data,

particularly the poor accounting of

intermittent streams.

4. For some States, and the region as a whole,

doubling the width of a riparian buffer from

30 to 60 m results in only a 49 percent

increase in estimated riparian area, due to

increasing overlap between adjacent riparian

areas as buffer width increases.

5. In the region, 72 percent of riparian areas are

in natural/semi-natural land use categories,

with forests making up the majority of this

total. Agricultural land use in riparian areas is

more important in the Farm Belt States 

(MO, IN, IL, IA), but still less than 60 percent

of total riparian area.

6. Urban development in riparian areas is low for

the region as a whole, and in each State,

totaling no more than 4 percent of any State’s

total riparian resource.

7. Condition of the watershed outside of the

riparian area is not accounted for in our

assessment of land use, but has a large

influence on water quality and aquatic 

habitat integrity not reflected in riparian 

land use and condition.

Key Points
25

Hanowski, J.M.; Wolter, P.T.; Niemi, G.J. 2000.

Effects of riparian buffers on landscape

characteristics: implications for breeding birds.

In: Wignington, P.J., Jr.; Beschta, R.B.L., eds.

Riparian ecology and management in multi-land

use watersheds. Proceedings of the Journal of

American Water Resources Association: 523-528.

Ilhardt, B.L.; Verry, E.S.; Palik, B.J. 2000.

Defining riparian areas. In: Verry, E.S.;

Hornbeck, J.W.; Dolloff, C.A., eds. Riparian

management in forests of the continental eastern

United States. Boca Raton, FL: Lewis Publishers:

23-42.

Michener, W.K.; Blood, E.R.; Brim Box, J.M.;

Couch, C.A.; Golladay, S.W.; Hippe, D.J.;

Kirkman, L.K.; Mitchell, R.J.; Palik, B.J. 1998.

Tropical storm flooding of a Coastal Plain

landscape. BioScience. 48: 696-705.

Minnesota Department of Natural Resources.

2001. Riparian forests in Minnesota: a report to

the state legislature.

Palik, B.J.; Michener, W.K.; Mitchell, R.J.;

Edwards, D. 1999. The effects of landform and

plant size on mortality and recovery of longleaf

pine during a 100-year flood. Ecoscience. 

6: 255-263.

Palik, B.J.; Zasada, J.; Hedman, C. 2000.

Ecological considerations for riparian

silviculture. In: Verry, E.S.; Hornbeck, J.W.;

Dolloff, C.A., eds. Riparian management in

forests of the continental eastern United States.

Boca Raton, FL: Lewis Publishers: 233-254.

Shifley, S.R.; Sullivan, N.H. 2002. The status of

timber resources in the north central United

States. Gen. Tech. Rep. NC-228. St. Paul, MN:

U.S. Department of Agriculture, Forest Service,

North Central Research Station. 50 p.

Verry, E.S.; Hornbeck, J.W.; Dolloff, C.A., eds.

2000. Riparian management in forests of the

continental eastern United States. Boca Raton,

FL: Lewis Publishers. 402 p.

Literature Cited
Palik, Brian; Tang, Swee May; Chavez, Quinn. 

2004. Estimating riparian area extent and land use in the Midwest.

Gen. Tech. Rep. NC-248. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North

Central Research Station. 28 p.

This report quantifies the amount and land use/land cover of riparian area in the seven-State

Midwest Region of the continental United States. We estimate that riparian areas cover 8.9 to 

13.2 million hectares in the region and that approximately 72 percent of riparian areas support

natural or semi-natural land cover. 

Key Words: Riparian area, Midwest, riparian buffers, land use, land cover

About the Authors

Brian Palik is a Research Ecologist and

Project Leader for the USDA Forest

Service North Central Research Station,

Grand Rapids, MN.

Swee May Tang is a graduate student

at the University of Washington,

Seattle, WA.

Quinn Chavez is a GIS Specialist with

the USDA Forest Service Northeastern

Area State and Private Forestry,

St. Paul, MN.

Published by:

North Central Research Station

Forest Service U.S. Department of Agriculture

1992 Folwell Avenue

St. Paul, MN 55108

2004

Web site: www.ncrs.fs.fed.us

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