Soil potentials:A positive approachto urban planning

Looking at soil properties in terms of their potentialsrather than limitations is more likely to result in land useplans that are compatible with a community's needs.

DONALD E. McCORMACK

BBETWEEN 60 and 65 million acresor about three percent of our land

is now in urban use (8). This in-cludes land used for transportationsystems. There are roughly 150 mil-lion urban residents, so the amount ofurban land used per urban resident isabout 0.4 acre. We are now cultivat-ing 2.1 acres of cropland per capita.

It seems almost incredible that thespan between these two figures is asnarrow as it is. Certainly it is a trib-ute to the productivity of the Ameri-can farmer and the soil he tills. It ismade even more impressive by thefact that the value of our farm prod-ucts exported in 1973 was nearly $19billion or almost $400 for the averagefamily of four.

In the next 30 years it is estimatedthat 18 million acres of land will go tourban uses other than transportation(10). Each decade, an area largerthan the state of New Jersey will beurbanized.

A question vitally important to allAmericans is what land should beused for urban development? Howwe answer that question will deter-mine in a large measure the qualityof life and the productivity of the land

Donald E. McCormack is assistant directorof the Soil Survey Interpretations Division,Soil Conservation Service, U. S. Departmentof Agriculture, Washington, D. C. 20250.

for all uses in the future. Decision-makers, both in the market place andin city hall, must face this question bycarefully studying the long-term con-sequences and economic, social, andenvironmental impacts of land usechanges (1). The nature of our soils—their limitations and their potentials—is one of the key considerations inanswering this vital question.

Soil Limitations

For more than 10 years, extensiveuse has been made in urbanizing areasof the detailed information providedby soil surveys. To a large degree thisinformation has been used to identifysoil limitations that impose hazards tothe intended urban use. Where suchinformation was not used, many urbanresidents have encountered seriousproblems with their homes. Failuresof septic tanks systems, wet base-ments, cracked foundations and wallsdue to unstable soils, and flooding arecostly problems that plague manyhomeowners.

These soil-related problems are aresult of soil properties that preventproper performance. The problemscould have been anticipated and mea-sures taken to minimize failures if in-formation about the soil propertieshad been available.

Planning commissions, health de-partments, highway departments, local

governments, builders, developers, andothers are increasingly aware of thevalue of soil data in making decisions.Copies of soil survey field sheets,interpretive tables, and maps andpublished soil surveys are used direct-ly by many of these agencies and in-dividuals. Also, an increasing numberof communities have arranged for atechnical review by the local soil con-servation district of all requests forproposed developments. A principalpart of this review is reference to thesoil data and consideration of soilproperties that are likely to imposehazards on the intended use.

Most often this activity is orientedtoward avoiding problems, and thereare many outstanding examples wherethis approach has proved valuable.Most advantages of using soil surveydata in urbanizing areas that Klinge-hiel (12) listed in determining a high-ly favorable benefit-cost ratio (125:1)were of this nature. The fact that anarea has a severe soil limitation forbasements and septic tank absorptionfields due to a high seasonal watertable may be among the planner'smost powerful arguments against aproposed development.

The process of pointing out prob-lems is often immediately effective forthe same reason that a blind man ap-preciates knowing there is a cliff threesteps ahead of him. We may have little

258 JOURNAL OF SOIL AND WATER CONSERVATION

chance to influence his resolve to walkoff the cliff, if in fact he has chosento do so, but fortunately he usuallywishes to avoid disaster.

Land Use Regulation

Increasingly, devices other than zon-ing are being used to restrict land use.Denial of permits for septic tank ab-sorption systems due to slow soil per-colation rates, coupled with decisionsnot to extend sanitary sewers into se-lected areas, is proving effective. Taxpolicies have been legislated in manystates to provide relief for farms neardeveloping areas (9). Purchase ofdevelopment rights or their optionaldonation to the community, as nearYellow Springs, Ohio, is receiving moreattention.

Where building is done on soils withseverely limiting properties, some com-munities are passing ordinances thatrequire special designs to minimizethe poor performance that resultedwhen standard designs were used. Thevillage of Canfield, near Youngstownin northeastern Ohio, received an in-novation award in 1973 from the In-ternational City Management Associa-tion for its subdivision regulations thatvary the design requirements forhouses according to the kind of soilas indicated by soil surveys (2). Thedesign of basement walls, includingthe use of pilasters and reinforced con-

crete, to resist high shrink-swell; ofwider foundation footings for soilswith low strength; of special drainagepractices for basements; of limits indepth to the basement floor; and ofstreet pavements in subdivisions arebased on the kind of soil (6). Con-sidering the vast amount of informa-tion provided by soil surveys, it seemsincredible that many building codesstill require the same design for theabove elements of home constructionfor all homes built within their juris-diction, giving no consideration to thewide range of unique kinds of soilsthat occur there.

Zoning has been considered a validexercise of the police power of gov-ernment, whereby the public health,safety, and welfare are protected(13). In the recent Wisconsin case ofJust v. Marinette County, the courtsupheld zoning based on the eminentdomain power of government, claim-ing that eminent domain is exercisedwhen the government wishes to re-strict a person's use of his land tosecure an affirmative benefit for thepublic (13). The lusts, who wereprevented from filling a marsh, weredenied the compensation usually pro-vided in cases of eminent domain.The court held that the only value tobe considered in determining the com-pensation is that based on the use ofthe land in its native state. It will be

very interesting to see how this deci-sion affects the application of zoningin the future.

Maximum Net Productivity of Land

At any point in time, in spite of ourinability to specifically define it (orachieve it), there exists that uniqueset of uses of available resources thatresults in the maximum net produc-tivity of land. The naturalist, thefarmer, the developer, and others havetheir own ideas about what the pri-orities should be.

Complex as its solution may he,there exists a formula for weighingand integrating the many opinionsand factors that impinge on this issue.Most people would agree that maxi-mizing alternatives for future useshould be included and given consid-erable weight in such an equation.

Too vague, too complex, too hypo-thetical, too idealistic—these are com-mon reactions to the above definitionof maximum net productivity of land.Defined in these terms, productivityis so interwoven with the aspirationsof people that many social objectivesare inseparable from the obvious eco-nomic implications. Crazy Horse, thegreat war chief of the Oglala Sioux,was quoted as saying, "One does notsell the earth on which the peoplewalk" (15). The concept of propertyand the rights that go along with its

NOVEMBER-DECEMBER 1974 259

ownership will, of necessity, gradual-ly change as the needs of an increas-ing population impact on dwindlingor at least finite resources.

Environmental quality has been con-sidered diametrically opposed to in-creasing levels of production or de-velopment by rhost conservationists.It is painfully obvious that in manycases progress, as normally defined,has come at the expense of environ-mental values.

When changes are considered in theuse of soils or other resources, waysshould be sought to minimize thedegradation of air quality, water qual-ity, and other aspects of the environ-ment. The choice of which land touse for given kinds of developmentis in most cases a vitally importantdeterminant of the impact on environ-mental quality. The study of ways todesign a development on given kindsof soil to minimize adverse environ-mental impacts also is needed, bothbefore a site is selected and as plansare made for its development.

In the long run there is no way thatthe net productivity of land can bemaximized without also maximizingenvironmental quality. Each newproject that is built without properlytaking into account environmentalquality will result in unnecessary pol-lution or deletion of values that willsubtract from the maximum net pro-ductivity of the land.

Odum (14) defined ecosystems asareas of nature that include living or-ganisms and nonliving substances in-teracting to produce an exchange ofmaterials and energy between the liv-ing and nonliving parts. Increasingemphasis is being given to the con-sideration of ecosystems in land useplanning, especially by environmental-ists. Many environmental values canhe maintained if existing ecosystemscan be preserved or properly man-aged. However, many people whodefine and interpret ecosystems do notgive proper weight to the soil thatsustains them.

It is interesting that in his discus-sion of ecosystems, Odum (14) citedthe most striking contrast between apond and a terrestrial ecosystem asbeing the size of green plants. Per-haps statements such as this result inthe lack of proper attention to thedifference in the sustaining mediumamong many who apply these con-cepts. Odum later referred to soil as

a highly developed ecological sub-system that determines the nature ofterrestrial ecosystems.

It is estimated that about 95 per-cent of the living organisms sustainedby soil are within the soil rather thanabove the soil surface (5). There areabout 100,000 different kinds of soilin the United States (17). No two ofthese soils have exactly the same com-bination of the five factors of soil for-mation—parent material, climate, liv-ing organisms, relief, and time or age.Because most of the factors that deter-mine the native terrestrial ecosystemsare controlled by the soil, and in factmost living organisms making up theecosystems are within the soil, anydefinition of the term that does notinclude the kind of soil as a centralfeature is incomplete.

The same kind of soil obviously maysupport several different kinds of eco-systems, depending on what man hasdone with the land. The best prospectfor predicting the impact of man'saction on ecosystems is to evaluate thenature of the soil before the actiontakes place, determine the soil prop-erties that will influence the ecosys-tem after land use is altered, and pre-dict the nature of the ecosystem afterthe change is made. Often it is pos-sible to examine land nearby where asimilar change in use was made onthe same kind of soil and with thesame vegetative community to verifythis prediction. Kinds of ecosystemshave little interpretive value unlessthe kind of soil is included in theirdefinition.

Positive Approach to Urban Planning

The outlook for continuing successin urban planning over a long periodof time is much greater when theeffort is centered around the positiveobjective of maximizing the net pro-ductivity of the land rather thanaround the objective of avoiding prob-lems or nuisances. Evaluation of al-ternative plans, each of which por-trays attempts to use available re-sources to their potential, is most like-ly to result in plans that are compati-ble with a community's needs.

There is a tendency for planners tospeak of soil suitability when they dis-cuss the merits of various land useproposals (3). Usually they are equat-ing soils with severe limitations topoorly suited soils and soils with slightlimitations to well suited soils. In

some urban areas such a conversionof terminology is valid. For manyareas it is not.

For more than 10 years soil inter-pretations for nonfarm land uses havebeen presented largely through theidentification of the degree and kindof soil limitation. Presentation accord-ing to soil suitability was rejected forseveral reasons. Foremost among thesereasons were (a) the fact that a site'soverall suitability is determined by agreat many things other than thenature of the soil, (b) an awarenessthat soil limitations can be overcomeby proper design, and (c) the lack ofextensive data about the performanceand cost of potential practices forovercoming soil limitations in specifickinds of soil.

As a result of presenting interpreta-tions on the basis of limitations, theuse of soil data has been incomplete.An analogy to conservation planningfor a farm illustrates the problem.

Suppose a conservationist visits afarm, discusses the farm's conservationneeds, and presents alternatives show-ing the farmer the importance of con-servation treatment and wise use ofhis land. Referring to the soil survey,the conservationist points out to thefarmer that a sloping soil is highlyerodible when it is used for cultivatedcrops. He also points out a nearbyarea of nearly level soil that would bebetter for cultivated crops becausethere would be little erosion, but henotes that it has a severe wetnessproblem. About this time the dialogueends, and the farmer is left to deter-mine how he should use the factsgiven to him. Indeed, this is a veryincomplete approach to conservationplanning if we assist the farmer no fur-ther, yet in many cases we go no fur-ther in assisting the urban planner orother officials of local government.

Soil potentials provide a positivebasis for proceeding through the ap-plication of facts about soil propertiesand limitations to planning for spe-cific objectives. Planners seek ways offitting the growth of urban areas tothe limitations of the environment (3 ).Where it is feasible, economically andenvironmentally, to overcome limita-tions to meet the needs of society, itmay be logical to use soils for a givenpurpose for which they have severelimitations. The principle is followedin conservation farm planning. It isone of the basic assumptions in the

260 JOURNAL OF SOIL AND WATER CONSERVATION

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land capability system, in which thecapability class is assigned on thebasis of continuing limitations afterthe application of feasible practices(16). Much of the nation's corn cropis produced on soils that in their nat-ural state have severe limitations forgrowing corn.

Soil potential has been defined asthe ability of a soil to produce, yield,or support a given structure or activityat a cost expressed in economic, social,or environmental units of value (11).As previously indicated, among thevarious kinds of inventories of naturalresources, the soil survey has the high-est interpretive value for most aspectsof urban planning. If we define thekind and extent of man's activity, wecan predict the ecosystem, the amountof runoff and erosion, and most otherof the elements that determine envi-ronmental quality and productivity.

In determining soil potential it isessential that the practices that mightbe used to overcome the soil limita-tions be identified, as well as theircost and an estimate of any continu-ing limitation after they are installed.This procedure is used with the farm-er in the above example when thealternatives of contouring, striperop-ping, or terracing are considered sothat cultivated crops can be grown onthe sloping soil.

Increasing data are available onpractices that can be used to over-come soil limitations for nonfarm landuses. For example, use of perimeterdrains around absorption fields canimprove the function of septic tanksystems on some soils with seasonalhigh water tables ( 4). The "Texasslab" can be used on soils with highshrink-swell potential to assure stablefoundations, or steel-reinforced con-crete basement walls can be used insuch soils (6). Basements can be elimi-nated altogether, provided with in-creased drainage, or placed at a shal-lower depth in wet soils.

It is not possible to completelyweigh the alternatives in land useuntil the full range of such practicesis identified. Identification of thesepractices is necessary before an arrayof soil potentials can be developed, atask that should be given high priorityin the next few years. Local informa-tion about "what works" in overcom-ing soil limitations must be recordedby kinds of soil.

For many communities, it is not

Soil Conservation Service photo

Sloping soil with a good potential for pas-ture may have a poor potential for housingbecause of the erosion hazard.

,TSoil Conservation Service photo by Cole

Gullying threatens this home because thecommunity's building code did not ade-quately consider soil stability in specifyingdesign criteria.

Building on soft organic soil resulted inthis subsidence problem. Use of soil sur-veys can prevent the use of such soils forhouses and other buildings.

by

NOVEMBER-DECEMBER 1974

261

physically or socially possible to lo-cate all urban development on soilswith slight limitations for the requiredland uses. In fact, in some communi-ties all the soils may have severe limi-tations for some kinds of urban devel-opment. For example, all the soilsaround New Orleans, Louisiana, havesevere limitations for dwellings due toflooding, high water tables, or un-stable soils. Some soils, however, aremuch more favorable than others.

Obviously there will be no mora-torium on building homes in the NewOrleans area because of these limita-tions. Local builders have found waysof providing protection against flood-ing; they provide drainage; and theydesign foundations that will supportthe loads. By Ohio standards thesepractices are prohibitively expensive,but it is not necessary in Ohio com-munities to build on soils with suchsevere limitations.

Some wet soils in the New Orleansarea are much wetter than others.Some unstable soils are much moreunstable than others. Some soils floodmuch more frequently and more deep-ly than others. By evaluating the limit-ing soil properties and considering therelative cost of overcoming the limi-tations, it is possible to identify thosesoils best suited for building and thoseleast suited. All the soils in the areacan he ranked in terms of relative suit-ability; and through this ranking, soilshest suited for building homes can beidentified. Even though these soilsmay be more limiting than the poorestsoils in some Ohio communities, sucha ranking of soil potentials is a power-ful tool in planning.

Fortunately most communities havesoils that are much better suited forbuilding than those in the vicinity ofNew Orleans. But for these commu-nities it is still important to develop aranking of soil potentials. Assume, forexample, that all soils have slight limi-tations for building. Depending onlocal objectives, some of these soilsmight be considered poorly suited forbuilding because they are highly erod-ible during construction, because soi.reaction is not acid enough to growthe azaleas prized by the local resi-dents, because they are too coarse intexture in the lower horizons to prop-erly filter effluent from septic tanks,because they are highly productive forimportant cultivated crops, becausethey arc ideally suited for intensive

recreation sites, or for many otherreasons.

It is essential that local objectivesbe listed, discussed thoroughly, andagreed to before the task of develop-ing an array of soil potentials begins.Such an activity is a logical functionof the local planning organization, asis the ensuing ranking of the soils, andit cannot be separated from local ob-jectives if it is to be useful.

This approach has been callededaphic planning (11). The profes-sional planner who elects to followthis approach can expect to obtain awide scope of support and assistancefrom conservationists, natural scien-tists, citizen groups, and individualsconcerned about the quality of theenvironment. Assistance from the soilscientist and soil conservationist, aswell as the engineer, sanitarian, bi-ologist, and related professions, willhe required to develop the most mean-ingful array of soil potentials.

Application of soil potentials toplanning in areas broader than thelocal community also holds promiseas a tool for fitting land use plans andpolicies to limitations and potentialsof the environment. Councils of gov-ernments covering several counties canmake good use of an array of soil po-tentials, along with a generalized soilmap covering the counties, in planningfor transportation networks, waste dis-posal systems, park and recreationsystems, preservation of prime farm-land, and other elements of land use.There are now 328 such councils inthe United States (7). Likewise, stategovernments, multistate regions, andthe federal government can make ex-tensive use of soil potentials.

At each level the ratings of soil po-tentials for individual kinds of soilmust be relative to all other soils inthe area covered. Soils rated poor ina few local communities may be fairor good in the larger region or viceversa. As in developing such arraysfor local communities, it is necessarythat objectives in land use for thelarge areas be identified.

Conclusion

It is not inevitable that our citiesgrow as massive amoebae, spreadingacross the land, eliminating irreplace-able resource potentials, and creatingserious environmental problems withfingers of strip development or col-onies of leapfrog development that

limit the alternative future uses oflarge areas of land. Soil potentialsprovide a valid basis for a positiveapproach to making land use deci-sions that will help insure the best useof the vast land resources of this coun-try. Through use of the soil poten-tial concept, such planning will helpachieve the maximum net productivityof the land-a worthy goal for us all.

REFERENCES CITED1. American Assembly. 1974. Land use in

America. Report of the 45th AmericanAssembly, Harriman, N. Y., April 1974.Columbia Univ., New York, N. Y.

2. Baker, W. B. 1973. Soil surveys-abase for building codes. Public Manage.(May): 9-10.

3. Bauer, K. W. 1973, The use of soilsdata in regional planning. Geoderma10: 1:1-26.

4. Bouma, J., W. A, Ziebell, W. G. Walker,P. G. Olcott, E. McCoy, and F. D. Hole.1972. Soil absorption of septic tank ef-fluent. Inf. Circ. No. 20. Dept. Soil Sci.and Bact., Univ. Wisc., Madison.

5. Buckman, H. D., and N. C. Brady.1969. The nature and properties of soils.Macmillan Co., London, Eng.

6. Canfield Planning Commission. 1966.Canfield subdivision regulations. Can-field, Ohio.

7. Croke, E. J., K. G. Croke, A. S. Ken-nedy, and L. J. Hoover. 1972. The re-lationship between land use and environ-mental protection. Joint Rept., Presi-dent's Water Pollution Control Adv.Bd., and Air Quality Adv. Bd. Wash-ington, D. C.

8. Frey, H. T. 1973. Major uses of landin the United States: Summary for 1969.Agr. Econ. Rept. No. 247. Econ. Res.Serv., U. S. Dept. Agr., Washington,D. C.

9. Hady, T. F., and A. G. Sibold. 1974.State programs for differential assess-ment of farm land and open space. Agr.Econ. Rept. No. 256. Econ. Res. Serv.,U. S. Dept. Agr., Washington, D. C.

10. Jackson, Sen. H. 1974. Speech intro-ducing proposed land use bill to theSenate. In Land Use and the Environ-ment: An Anthology of Readings. Am.Soc. Planning Officials, Chicago, Ill.

11. Johnson, W. J., and L. J. Bartelli. 1974.Rural development: Natural resourcedimensions. J. Soil and Water Cons. 29:L:18-19.

12 Klingebiel, A. A. 1966. Costs and re-turns of soil surveys. Soil Cons, ( Au-gust ): 3-6.

13. Large, D. W. 1973. This land is whoseland? Changing concepts of land asproperty. Wisc. Law Rev. 1973(4 ):1,039-1,083.

14. Odum, E. P. 1971. Fundamentals ofecology. W. P. Sanders Co., Philadel-phia, Pa.

15. Sandoz, M. 1945. Crazy Horse, thestrange man of the Oglalas. Knopf,New York.

16. Soil Conservation Service, U. S. Depart-ment of Agriculture. 1966. Land capa-bility classification. Agr. Handbook No.210. Washington, D. C.

17. Soil Survey Staff, Soil Conservation Ser-vice, U. S. Department of Agriculture.1974, Soil taxonomy: a basic system ofsoil classification for making and inter-preting soil surveys. Agr. HandbookNo. 436. Washington, D. C. q

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