678 Korean Journal of Soil Science and Fertilizer Vol. 51, 4, 2018 Introduction 토양침식은표토가물이나바람에의해원래의위치에서분리되어다른곳으로이동하여유실되는현상을말하며삼림벌채, 과다경작, 과다방목등이가장주요한원

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1 Korean J. Soil Sci. Fert. Vol.51, 4, pp , 2018 Korean Journal of Soil Science and Fertilizer Article pissn : eissn : A Study on Efficient Management Strategy for Soil Erosion Joung-Bae Hwang*, Nam-Chan Kim 1, Chang-In Lim 1, and Yoon-Min Kang 1 Hyundai Engineering Co., Ltd, Seoul 03058, Korea 1 Department of Enviromental Engineering, Kwangwoon University, Seoul 01897, Korea *Corresponding author: jbhenv@naver.com A B S T R A C T Received: November 28, 2018 Revised: December 5, 2018 Accepted: December 5, 2018 Soil value was estimated 26 trillion Korean won and recent climate change due to global warming is highly affecting soil erosion. Especially, about 10% of surface soil was annually eroded because of massive construction in Korea. Main purpose of this research was i) to investigate occurrence, mechanism, affecting parameters of soil erosion especially focused on wind erosion and ii) to conduct wind tunnel experiment for evaluating feasibility of dry fog system in stabilizing wind erosion. Result of wind tunnel experiment showed that wind erosion could be reduced about 22-38% after applying dry fog system. Two parameters, soil particle size and spreaded water drop size, are main parameters to affect efficiency of wind erosion stabilization and smaller water drop size is more effective to prevent wind erosion than soil particle size. In terms of wind erosion management, evaluation of soil erosion should be conducted for environmental impact assessment (EIA) when land usage is changed or massive construction was conducted. Since there is no evaluation form of soil erosion in EIA, not only soil erosion but also wind erosion evaluation should be included in the EIA. In addition, transaction of soil and rock open portal recycle system (TOCYCLE) could be utilized to recycle surface soil and consequently, prevent wind erosion and conserve value of soil. Overall, dry fog system is an effective technique for wind erosion preventing system and it could be combined with natural and/or artificial soil conservation system to enhance wind erosion prevention. Furthermore, policy and management system for preventing soil erosion should be thoroughly reviewed to make better soil conservation. Keywords: Weathering, Top Soil, Soil Erosion, Conservation of Surface Soil m/sec 6m/sec 8m/sec 먼지침적량 ( g/m 2 ) Soil reduction (g/m 2 ) 이격거리 ( m) Distance (m) Soil Reduction by Wind Speed and Distance. C The Korean Society of Soil Science and Fertilizer. This is an Open Access article distributed under the terms of the Creative Coons Attribution Non- Coercial License ( which permits unrestricted non-coercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 678 Korean Journal of Soil Science and Fertilizer Vol. 51, 4, 2018 Introduction 토양침식은표토가물이나바람에의해원래의위치에서분리되어다른곳으로이동하여유실되는현상을말하며삼림벌채, 과다경작, 과다방목등이가장주요한원인이다. 이는인간활동에의해교란받지않은자연조건에서주로일어나는현상이지만최근들어인위적으로삼림을포함한지표식생의벌목을통해대규모개발사업을시행하는과정에서표토가유실되는현상이점차증가하고있다. 토양침식은각종농경및산림활동에의한자연적인침식과관개용수및생활용수, 공업용수등의취수와하천주변의도시화및공업화등인류의산업활동에따른인위적인침식으로구분된다. 또한, 침식작용인자에따라수식 (Water Erosion), 풍식 (Wind Erosion), 빙식 (Ice Erosion), 설식 (Snow Erosion), 생물적침식 (Biological Erosion) 등으로구분할수있으며, 대부분의토양침식은수식과풍식에의해발생하는것으로조사되었다. 전세계적으로자연적인침식과인위적인침식과의관계는명확이밝혀진것은없지만, 지형이손상되지않은자연적으로안정적이거나인간활동에의해안정화된지역 ( 사용되지않은불모지포함 ) 에비해인간에의해개발되어토양유실의영향을받는지역이차지하는비율이 3배정도많으며, 사람에의해인위적으로훼손되는유실은물 55.6%, 바람 27.9%, 화학작용 12.2%, 물리적작용 4.2% 순으로조사되어물에의한토양유실면적이가장큰것으로조사되었다 (Oldman, 1991). 우리나라경우토양침식으로인한연평균표토유실량은 50톤 /ha 이상으로전국토의 20% 수준인것으로조사되었으며, 권역별로는강원, 경남, 전남지역에서수계별로는한강권역에서높은수준의토양유실이파악되었으며인위적침식량평가결과표토를직접적으로개발하는면적의연간개발면적의 10% 가유실되고있다고추정하였다 (MOE, 2013). 토양침식에따른국내 외의표토관리방안은국내의경우관계부처협동으로수립한제2차비점오염원관리종합대책 ( ) 에준하여표토를관리하고있는데먼저환경부에서는비점오염원저감관점에서흙탕물저감사업등하천으로의토사유입방지대책을실시하고있으며, 농림부는농업생산성유지관점에서밭기반정비사업, 토양유실및토양양분유출을연구수행하고, 산림청은산림자원보전을위해임도관리를강화하고토석채취를제한하는등각기관별로비점오염원관리의보조적측면에머물러있어표토보전을목적으로하는체계적관리가필요한것으로조사되었다. 또한, 해외의경우독일행정부는표토의보호위반시형사처벌대상과벌과금을부여하고있으며, 미국은토양보전법에의거사전예방적토양자원보전정책을, 캐나다는토지소유자에게토양침식복구의무규정등각국가별로표토보전을위한제도확립및관리주체를선정하여표토유실을적극적으로방지하는등표토관리를하고있다 (MOE, 2013). 따라서, 표토는사람들의활동으로인한무분별한개발과과도한토지이용, 이상기후에가까운집중호우등의영향으로토양침식에취약한상태이기때문에, 침식으로인한생태계의훼손, 수질오염등의문제점이야기되고있으며특히, 훼손된토양의경우재생속도가상당히느려재생이불가능하기때문에효율적이고체계적인표토보전및관리가요구된다. 국내토양환경정책의패러다임이오염토양의정화및복원에서토양그자체가하나의자원으로서 표토 를적극적으로보전하는방안으로정책계획이변화되고있다. 이에국내 외토양침식으로인한환경문제를면밀히조사하여토양침식을저감할수있는방안에대하여제도적 기술적인측면으로구분하여적용할수있는토양침식의효율적인관리방안에대하여제시하였다.

A Study on Efficient Management Strategy for Soil Erosion 679 Materials and Methods

함수량은온도 110±5 C의건조로에의해젖은흙에서제거된수분의양을말하며, 흙의함수량과건조된흙의무게의비를흙의함수비, 흙의비중은 4

또한, 흙의액성한계는소성상태에서액성상태로변하는순간의함수비로액상을나타내는최초의함수비를말하며, 흙의소성상태와반고체상태의한계를나타낼때의함수비를말한다.

흙의물리적특성을파악하기위한흙의분류는일반적으로통일분류법 (USCS) 을이용하는데이는공학이나지질학분야에서흙을입자의크기와입도분포, 소성성등의기준으로분류하는체계이다.

S-1 S-2 S-3 Fig. 1. Soil sample used in the experiment.

풍동실험은가급적현장과동일조건하에서실험을하여야하나현장조건이너무광범위하고주변지역의환경변화가많아이러한조건을모두고려하기에는다소어려움이있어외부의변화여건을최소화하기위하여폭 5 m, 높이

3 A Study on Efficient Management Strategy for Soil Erosion 679 Materials and Methods 실내토질시험실내토질시험은토사층의물리적특성을파악하여흙을분류하고자하는데그목적이있으며실내토질시험을위한시험종류는함수비, 비중, 액성한계, 소성한계, 입도분석등이있다. 함수량은온도 110±5 C의건조로에의해젖은흙에서제거된수분의양을말하며, 흙의함수량과건조된흙의무게의비를흙의함수비, 흙의비중은 4 C에서증류수의단위중량에대한흙입자의단위중량의비를말한다. 또한, 흙의액성한계는소성상태에서액성상태로변하는순간의함수비로액상을나타내는최초의함수비를말하며, 흙의소성상태와반고체상태의한계를나타낼때의함수비를말한다. 흙의입도분석시험은입자의크기및분포를알기위한흙의가장기본적인시험이며, 흙입자의크기는침하, 전단강도, 투수, 동상등흙의공학적성질에큰영향을미치며이시험결과에의해흙의세밀한분류를할수있다. 흙의물리적특성을파악하기위한흙의분류는일반적으로통일분류법 (USCS) 을이용하는데이는공학이나지질학분야에서흙을입자의크기와입도분포, 소성성등의기준으로분류하는체계이다. 금회연구에서는풍동실험을위한토양시료는현재공사중인토목공사건설현장에서토양시료 3종 (S-1, 2, 3) 을채취하여실내토질시험을실시하였다 (Fig. 1). S-1 S-2 S-3 Fig. 1. Soil sample used in the experiment. Test House 풍동실험은가급적현장과동일조건하에서실험을하여야하나현장조건이너무광범위하고주변지역의환경변화가많아이러한조건을모두고려하기에는다소어려움이있어외부의변화여건을최소화하기위하여폭 5 m, 높이 3 m, 길이 12 m의 Test House를설치하여기상조건변화를최소화하였으며건설현장에서일어날수있는풍속조건을만들어풍동실험을하였다. 또한, Test House 측면에개폐가가능한시스템을두어실험이끝날때마다환기를시켜실험의정확도를향상시켰다. 건설현장에서발생하는토양풍식현상을 Test House내에서재현하기위하여토양시료를지속적으로공급할수있는토사공급장치, 토사를지속적으로흩날리도록하기위해지속적인바람을만들수있는송풍기, 풍속을조절할수있는자동제어기기, 토사의확산에따른침적량을확인하기위한계측기기등을준비하였다 (Fig. 2). 또한, Dry Fog System ( 이하 DFS ) 의침적효과를알아보기위하여 Fogging시실험에서사용할 2류체원추형노즐은평균입자직경이 100 μm이하에서미세하게분무할수있는노즐이다.

4 680 Korean Journal of Soil Science and Fertilizer Vol. 51, 4, 2018 None- Fogging Fogging Fig. 2. Wind tunnel experiment (None-Fogging, Fogging). 풍동실험방법본실험을위해채취된시료는토사풍식이용이하도록 Wire Mesh 채를이용하여풍동실험용입자를확보하였으며, 실내토질시험결과함수율이 % 로시료가수분을포함하고있어실험에바로사용하기에어려움이있을것으로판단되어함수율을줄이기위한전처리가필요하였다. 따라서, 채취한토양시료를 Test House에서약 10일동안건조시킨후토양수분측정기를이용하여수분함량이최소화될때까지전처리를하였다. 이는풍동실험에서수분함유에따른입자간의점착력을최소화하기위함이었으며, 저감효과및정확도를극대화하기위함이었다. 토사공급장치에서토사확산지점으로부터 2 m를시작으로 1 m 간격으로 10 m까지시료채취판을설치한다. 특히시료채취판내에는잔량측정을위한 GF/C Filter 일정크기 ( cm) 로잘라사용한다. 풍속조건은토사흩날림정도가건설현장의토양유실과최대한가깝도록재현하기위하여보버트의풍속등급을고려하여산들바람 (4 m/s), 건들바람 (6 m/s), 흔들바람 (8 m/s) 등 3가지의인위적인풍속조건을만들어실험을하였다. 토사공급장치에서나오는토사는송풍기를이용하여각풍속별로약 5분동안지속적으로토사시료확산시킨후, 시료판에충분히침적될수있도록한후시료판을수거하여시료판내 GF/C Filter 무게를측정한후여지무게를제외하여침적량을측정하였다. 또한, 동일한방법으로토사공급장치후단에토양풍식의저감기술의하나인 DFS를설치하여 Fogging으로인한침적량을조사하여 Fogging 전 후의풍속및이격거리별로토사침적량변화를조사하였다. Results and Discussion 토사의물리적특성과분류결과풍동실험을위하여건설현장에서채취한토사시료 3종 (S-1, 2, 3) 에대하여한국산업규격 (KSF) 에따른실내토질시험결과함수율 %, 비중 g/cm 2, Atterberg 한계시험결과비소성및소성지수가작은것으로조사되었다. 체분석결과 200 (0.075 ) 체기준으로 % 까지통과된것으로나타났으며, 모든시료의균등계수 (C u ) 는 , 곡률계수 (C g ) 는 로조사되었다. 또한, 통일분류법 (USCS) 에의한분류결과시료모두실트질모래 (SM, silty sand) 인것으로조사되었다 (Table 1).

5 A Study on Efficient Management Strategy for Soil Erosion 681 Table 1. Results of Sieve Analysis. Sample Sieve Sieve Size () Grain Size Distribution (%), Finer than Uniformity Coefficient, Coefficient of Gradation D85 D60 D30 D15 D10 Cu Cg S SM S SM S SM USCS Remark 토양침식관리방안 ( 제도적인방안 ) 토양침식은한번발생하면재생하기에어려움이있기때문에반드시사전예방이필요하다. 이에사전예방적정책수단의하나인환경영향평가제도는개발사업단계에서표토의보전및침식예방을위한유일한수단이나 환경영향평가서작성등에관한규정 에의하면수질항목에서토사유출량, 토양항목에서토양오염등각항목에대한영향예측및저감대책을수립제시하는것으로되어있어환경영향평가서에는토양침식 ( 유실 ) 과관련된내용을다루지않고있는실정이다. 따라서, 제도적으로보완하기위하여환경영향평가서 토양 항목에표토에대한현황조사및표토유실에대한영향예측, 저감대책등을환경영향평가서에포함시켜작성할수있도록 환경영향평가서작성등에관한규정 ( 안 ) 을개정하여각종개발사업시행에따른표토유실에대한영향을최소화하여야할것으로사료된다. 국토해양부에서우리나라건설공사현장에서발생하는사토, 순성토의정보를체계적으로종합관리하여토석자원을재활용하고불필요한국토환경훼손을방지하기위하여 토석정보공유시스템 (TOCYCLE, Transaction of soil&rock Open portal recycle system) 을운영하고있는데, 이는토석자원의재활용을통해신규토취장개발을줄여표토와자연환경을간접적으로보호할수있는시스템이다. 특히, 대규모개발사업초기에현장에서발생하는사토 ( 비옥토포함 ) 의경우건설폐기물의관점에서재활용되기때문에표토의가치가상실된채재활용되고있는실정이다. 따라서, 토석정보공개전에사토와비옥토를구분하여활용가치가높은비옥토는각현장별로재활용계획을수립하여활용한다면표토의보전측면으로는최선의방법이라사료된다. 토양침식관리방안 ( 기술적인방안 ) 완충식생대, 식생밭두렁, 수로형시설, 낙차공, 침사지, 경사면보호공등은고랭지밭에서강우시유출되는흙탕물을저감하기위한자연적인침식방지공법으로이저감시설은국내건설현장에서일반적으로많이사용하고있는공법이기도하다. 그러나, 공사현장에서저감시설의설치위치및운영방법, 유지관리등이원활하게운영되지않고있어이를보완하기위하여 환경영향평가법 에의한 사후환경영향조사 시환경부와협의된협의내용의관리즉, 저감시설설치및관리에대한모니터링을지속적으로관리하여야한다. 일반적인건설현장에서토양유실이일어날수있는주요공종은토공공종으로토공굴착작업과운반작업시발생할수있으며, 공사장비의이동및토사상 하적시, 토사적치장에서바람과강우에의해토양침식이발생한다. 특히, 발전소, 제철소등과같은대규모건설현장적치장에서침식 ( 풍식 ) 에의한영향을최소화하기위한인위적인침식방지공법으로지속적인살수, 방진망덮개, Dry Fog System ( 이하 DFS ) 과, 화학적먼지억제제 ( 계면활성제, 폴리머, 역청등 ) 등이활용되고있다. Dry Fog System ( 이하 DFS ) 은 U.S. EPA에서석탄운반장비들의먼지저감기술로입증된최고의저감기술

6 682 Korean Journal of Soil Science and Fertilizer Vol. 51, 4, 2018 (BDT, Best Demonstrated Technology) 이라고하였으며 (EPA, 2009), DFS의먼지제거원리는 (Fig. 3) 에제시한바와같이먼지입자와미세수분입자의충돌을나타낸것으로먼지보다미세수분입자의크기가큰경우먼지입자가미세수분입자의주변공기흐름라인을따라흘러가버리는것으로알수있으며, 미세수분입자가먼지입자의크기가비슷하거나작은경우에는미세수분입자가공기흐름라인주변에서충돌을일으키면서미세수분입자속으로먼지입자가포집되는원리이다 (HHS.gov, 2012). Fig. 3. Effect of Droplet Size on Dust Particle Impingement. Fogging 전 후의토사침적량변화풍동실험을통한풍속및이격거리별토사침적량을조사한결과토양발생지점으로부터가장가까운 2m 지점에서대부분의토사가침적된것으로나타났는데, 이는토사의비중때문인것으로생각된다. 또한, 토사침적량은풍속이커질수록침적량은점차증가하고, 이격거리가멀어질수록침적량은감소하는것으로조사되어토사침적량은풍속과는비례하고거리와는반비례하는것으로조사되었다. Fogging으로인한토사저감량은약풍 (4 m/sec) 일때 g/m 2, 미풍 (6 m/sec) 일때 ( ) g/m 2, 강풍 (8 m/sec) 일때 ( ) g/m 2 로조사되었는데이격거리 2 m지점, 미풍 (6 m/sec) 이상에서먼지저감량이 (-) 값으로나타났는데이는바람발생지점으로부터가장가깝고풍속에의한밀림현상으로이동되었기때문인것으로생각된다. 또한, 이격거리별토사저감량은 2 m, 4 m, 5 m지점에서약풍 (4 m/sec) 일때최대가되며, 3 m지점에서미풍 (6 m/sec) 일때가최대이며, 6 m지점이후부터는약풍 (4 m/sec) 에서토사저감량이가장큰것으로조사되었으며, 저감효율은약 22-38% 정도의효과가있는것으로나타났다 (Table 2) (Fig. 4). DFS의토사제거효과는풍속이커질수록효과는증가하지만일정속도가이상이되면효과는점차감소될것으로예상되었는데이는토사입자와물입자의크기및풍속과의관계가 DFS 효율에영향을미치고있기때문일것으로사료된다.

7 A Study on Efficient Management Strategy for Soil Erosion 683 Table 2. Dust reduction and efficiency by wind speed before and after fogging (g/m 2 ). Distance (m) Dust reduction by wind speed Wind speed (4.0 m/sec) Wind speed (6.0 m/sec) Wind speed (8.0 m/sec) None- Fogging Fogging Soil 1) Efficiency reduction (%) None- Fogging Fogging Soil 1) Efficiency reduction (%) None- Fogging Fogging Soil 1) Efficiency reduction (%) ND ) Soil reduction = Fogging - (None-Fogging) m/sec 6m/sec 8m/sec 먼지침적량 (g/m 2 ) Soil reduction (g/m 2 ) 이격거리 ( m) Distance (m) Fig. 4. Soil Reduction by Wind Speed and Distance. Conclusions 본연구는전세계적으로지구온난화에따른기온상승과기상변화등이상기후로인하여강수량이줄고자연생태계가붕괴되면서토지의사막화가급격히가속화되어이로인한지표면이지속적으로건조화되고, 토양침식으로인한환경영향이대두되어이에따른토양침식의효율적인관리방안에대하여연구하였다. 토양침식의관리방안으로제도적인방법은표토의보전및침식예방을위한사전예방적정책수단의하나인 환경영향평가제도 는개발사업시표토유실에대한현황조사및영향예측, 저감대책등을다룰수있도록 환경영향평가서작성등에관한규정 ( 안 ) 을개정하여환경영향평가서를작성한다면표토유실에대한예방및보전효과가클것으로예상된다. 또한, 그동안 사토 의개념만적용하여재활용하기보다는토사처리개념의시스템을운용하였던 TOCYCLE은공사초기에사토와비옥토를먼저구분하여 TOCYCLE을통해활용가치를높여재활용하는것이표

8 684 Korean Journal of Soil Science and Fertilizer Vol. 51, 4, 2018 토의보전측면으로는최선의제도적인방법이라할수있다. 기술적인방안으로는국내건설현장에서일반적으로많이사용하고있는자연적인침식방지공법은 환경영향평가법 에의한 사후환경영향조사 시환경부와협의된저감시설의설치및운영여부에대한모니터링을지속적으로관리하여토양침식에대한영향을최소화한다. 특히, 기술적인저감시설의하나인 Dry Fog System은풍동실험을통해제거효과는토사먼지입자와물입자의크기, 풍속과의관계가저감효율에영향을미친다는것으로알수있었으며, 최고의효과를얻기위하여제거하고자하는토사의입자크기와풍속조건등에대한정보를사전에면밀히조사하여분석한후토사입자보다작은미세한물입자를만들어제어한다면충분한효과를얻을수있으며, 건설현장에서크라샤 (crusher) 등의장비운영및적치장, 비포장노면등에점차확대하여활용하면큰효과를거둘수있을것으로생각된다. 본연구결과토양 ( 표토 ) 의유실방지를위한제도적 기술적인방안을제시하였으며, Dry Fog System과같은기술적인방법들은지속적으로추가연구가필요할것으로사료된다. References ASTM Standard Test Method for Classification of Soils for Engineering Purposes. American Society for Testing and Materials. ASTM Designation D Annual Book of ASTM Standards, Section 4, Casagrande, A Research on the Atterberg Limits of Soils. Public Roads. 13(8): EU Hard surfaces. Hidden costs. Francis Beaufort. Beaufort Wind Scale. U.K. Royal Navy ( Korean Agency for Technology and Standards (KATS). 2006, Standard method of classification of soils for engineering purposes (KS F 2324). Korean Agency for Technology and Standards (KATS) Standard test method for particle size distribution of soils (KS F 2302). Korean Agency for Technology and Standards (KATS) Standard test method for liquid limit and plastic limit of soils (KS F 2303). Korean Agency for Technology and Standards (KATS) Standard test method for water content of soils(ks F 2306). Korean Agency for Technology and Standards (KATS) Standard test method for density of soil particles(ks F 2308). MOE A Study on the Conservation of Surface Soil and Erosion Control MOE Standard Design Guidelines for Muddy Water Reduction Facility. MOE Research on Value Evaluation and Examples for Soil and Groundwater. MOE Comprehensive Topsoil Conservation Plan ( 13-17). p MOE Guidelines for the Notification of Post-Environmental Impact Survey Results. MOE Regulations on the Preparation of Environmental Impact Assessment, Ministry of Environment Notice Oldeman, L.R., R.T.A. Hakkeling, W.G. Sombroek, 1991, World Map of the Status of Humaninduced Soil Degradation (GLASOD): An Explanatory Note. International Soil Reference and Information Centre. Wageningen U.S. Department of Agriculture (USDA). Soil Survey Staff Soil Survey Manual, USDA handbook no.18. U.S.

9 A Study on Efficient Management Strategy for Soil Erosion 685 Government Printing Office, Washington, DC. U.S. Department of Health and Human Services Dust Control Handbook for Industrial Materials Mining & Processing, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication (RI 9689), Jan;1-284 U.S. Environmental Protection Agency(EPA) in 40 CFR Part 60 Standards of Performance for Coal Preparation and Processing Plants; Final Rule, October 8.

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