• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2013-2018
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• 2007

최근에 발생하는 홍수특성은 단기간의 국지성 집중호우로 본류 대하천보다는 상류지역 지류하천이 특히 취약하여 이에 대해 하류보다는 상류, 본류보다는 지류위주로 과거와 다른 치수정책 전환이 요구되고 있다. 정부에서도 과거 치수대책이 제방위주의 선적인 개념에서 면적인 개념의 유역치수 중심의 방어형태로 추진하고 있으나, 상류지류 하천에 대한 홍수방어 계획은 부족한 실정이다. 지류하천에 홍수가 발생하면 홍수도달시간이 짧아 첨단홍수예보시스템으로도 대처가 곤란한 문제가 있으며, 이외에도 홍수와 함께 산사태가 빈번히 발생되고 토석류, 유목류가 한꺼번에 동반 유입되어 인명과 재산피해가 크게 발생하는 특징을 가지고 있다. 작년 7월 강원지역 집중호우에서도 인제군, 평창군 등 지류에 인명과 재산피해가 크게 발생한 것도 이와는 무관하지 않을 것이다. 최근 국지성 집중호우가 빈번히 발생하는 것은 기상적 측면이 아니더라도 우리나라는 하천경사가 급하고 산지가 국토의 약 70%로 구성되어 있어 지형적 측면에서 평화의댐(지체댐), 군남홍수조절지, 한탄강 홍수조절댐 등 대규모 홍수방어댐 도입시 홍수조절 효과가 우수하나, 대규모 댐건설에 따른 지역민의 불신, 환경단체 반발, 사회적 미합의 등 현실적인 제약조건이 많으므로 현실적이고 상류지역 지류하천에 효과적인 홍수조절을 위해서는 보호하고자 하는 도시 및 주요시설물시설에 대하여 소규모 홍수저류지(Detention Dam)를 상류 지류하천에 단일 또는 군(群)으로 도입하여 설치하는 방안을 적극적으로 추진하여야 한다고 사료된다. 소규모의 홍수저류지는 평상시에는 자연상태와 같이 전량 방류하고 갑작스런 홍수발생시 첨두홍수량을 지체하거나 감소시켜 하류지역에 홍수피해를 줄이는 시설로 기존의 댐보다는 규모가 적고 평상시에는 자연하천과 같이 물을 담지 않아 환경변화에 의한 영향이 적어 사회적 합의가 유리하고 친환경적이며, 홍수기에는 비어 있는 저류용량을 전량 활용이 가능하여 저수규모에 비해 홍수조절효과는 큰 장점이 있다. 특히 홍수조절의 본래 목적 외에도 초목류, 토석류 및 각종 부유쓰레기를 차단하는 사방댐 역할과 하류하천의 퇴사량 감소 등 다방면으로 효과가 있어 독일, 일본 등 선진국에서는 적극적으로 추진되고 있다. 본 연구에서는 선진 외국에 도입된 홍수저류지 사례를 조사 및 검토하여 국내에 적용 가능한 유역분담형 홍수저류지 규모 및 방식, 홍수저류지 도입방안과 향후 연구방향 제시하였다.

• Journal of Korea Water Resources Association
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• v.56 no.12
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• pp.837-844
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• 2023

Small and medium-sized mountain rivers that flow through steep, confined valleys carry large amounts of coarse-grained sediment and woody debris during floods. It causes an increase in flood water level by aggrading the riverbed and the cross-section blockage due to driftwood accumulation during flooding. However, the existing flood level calculation in the river basic plan does not consider these changes. In this study, using the Typhoon Hinnamnor flood in September 2022 as an example, we performed numerical simulations using the HEC-RAS model, taking into account the blockage of a cross-section at the bridge and changes in riverbed elevation that occurred during floods, and analyzed the flood level to predict flood risk. This study's results show that flooding occurs if more than 30% of the cross-section is blocked. The rise of flood water levels corresponds to that of the riverbed due to sediment deposition. These results can be used as basic data to prevent and effectively manage flood damage and contribute to establishing flood defense measures that consider actual phenomena.

• Journal of Korea Water Resources Association
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• v.46 no.9
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• pp.947-956
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• 2013

Most of flood protection walls built on the impingement in mountain rivers have been made of concrete. It may cause flood disasters because the smooth wall surface could increase flow velocity. In this study the hydraulic experiments was carried out to evaluate the effect of one side wall with rectangular vertical ribs on flow resistance in open channel. The ratio of the pitch between vertical ribs to its depth, ${\lambda}_{nv}$, was designed so that it include the so-called d type and k type roughness. The range of Froude number, $F_r$, based on hydraulic radius is 0.81~1.12. Flow resistance in the open channel with a rib sidewall depends on the interval length of each ribs and the flow discharge. Maximum flow resistance occurred when ${\lambda}_{nv}$ is 9. In the d type roughness which ${\lambda}_{nv}$ is less than 3, the flow resistance decreases with increase of flow discharge. In the k type roughness which ${\lambda}_{nv}$ is greater than 3, the flow resistance increases with increase of flow discharge. The increments of flow resistance are especially great when ${\lambda}_{nv}$ are 9 and 12. The resistance due to vertical rib is mostly by the shape resistance and the vertical rib on one sidewall of open channel affects on the flow resistance so that the equivalent roughness heights of vertical rib may occur in scale of flow depth. Therefore the vertical ribs may be used to reduce the flow velocity and to move the location of maximum flow velocity from the rib sidewall to the centerward in a cross section of channels.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.479-491
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• 2013

Products of the eruption of Mt. Baekdusan are identified as volcanic materials at the estuaries of the Songhuagang river to north, the Dumangang river to east and the Amnokgang river to west. More speficially, pyroclastic flows, lahars and volcanic floods can affect an area of 400km in radius, centering around Lake Cheonji caldera. However, unlike the millenium eruption, the flow situation has been changed. Because multi-purpose dams and reserviors with a combined pondage of mora than 2 billion tons of water have been built in the rivers of which sources are originated from Lake Cheonji caldera. In addition, the flow of fluids expected to take place when the volcano has erupted is thought to be affected by artificial constructions in both direct and indirect ways. This study calculates the direction of fluids flow by using numerical analyses of pyroclastic flows, lahars and volcanic floods that can occur when the volcano of Mt. Baekdusan has erupted. We also estimate the scope of damages by pyroclastic flows, lahars, volcanic flooding caused by the pondage of the dams and water storages in and around Mt. Baekdusan. Pyroclastic flows transported over the steep slopes at the early times of eruptions move over the mountain slopes, affecting airplanes, and lahars due to leaks of Lake Cheonji could reach as far as major rivers and streams near Mt. Baekdusan. Unlike historical accounts, volcanic flood is expected to be limited in its scope of influence to reservoirs bigger than Lake Cheonji in pondage.