圖書典藏及影音數位平台

古寧頭～嚨口於大金門西北側，因颱風或季風波浪侵襲，造成沿岸地形改變，經金門縣政府與當地居民反映，現況灘面較以往呈現侵蝕狀況。 由於此區域過去較少進行水深地形及波浪調查，因此有必要針對海象、地形水深、波浪及底質等進行調查，以供未來擬定海岸防護對策參考之依據。

First, origin and purpose In Kinmen coast there are many places in erosion phenomenon, marine meteorology basic survey data and the coast of topography is relatively insufficient, and lack of long-term observation data and systematic analysis. Therefore, this project installment segment for investigation and study, by the marine meteorology and topography investigation, cooperate with the numerical simulation analysis, proposing the segmentation method of coast erosion prevention and control strategy, in order to complete background investigation and coastal protection. Project zone in 2014 for coastline length from Cih-Ti to Shuei-tou port is about 5.2 kilometer. 2015 project area for Gu-ning-tou to Long-kou coast is about 5.0 km coastline length. Second, Field investigations The topography measurement- This year in May and September during twice topographic surveys has suffered Soudelor and with Lotus typhoons hit. Nearshore area (elevation 1 ~ 3 m) in Gu-ning-tou area appears slightly deposition; An-ci to Long-kou has slight erosion. Offshore area at the Gu-ning-tou of depth to 5 ~ 8 m in sedimentation, small deposition of the Jin-lie waterway with an obviously change, the remaining present slight erosion. Tide, waves and current analysis-This year in May and September are twice survey. Direction is given priority to with W to flood tide current, ebb tide is to give priority to E and surface current were greater than the middle, bottom. The first and second measurement current distribution is greater than 50 and 37.5 cm/s. Wave record shows for the first time, during the period of observation of wave height (H1/3) is 20.0 cm, the corresponding indicator period (T1/3) 3.79s, wave dir. to E, W, and ENE. During the second record is displayed, observation of wave height is 22.5 cm (H1/3), the corresponding period (T1/3) 3.20 s, wave dir. to E. At Shuei-tou port, tidal station (2014/3 ~ 2015/10) maximum tide level is 3.62 m, the lowest tide level is 3.29 m, the largest tidal range of 6.04 m. Spring average high tide level is 2.47 m. Tide is semidiurnal tide and main constituent elements are M2 and S2. Sediment analysis- This year in May and September are twice survey. Sampled five sections, a total of 20 points; high and low tide with 9 sampling stations, a total of 18 points; bed suspension sampling with three sections, a total of 6 stations; offshore current field investigation with bed suspended load station layout. a. Sample in sea- Inside Wu-jiang bay and nearshore median grain size is given priority to with silt; sea side is given priority to with medium sand. The particle size distribution of Wu-jiang bay is roughly parallels the coast, present to the diminishing coast distribution. A coarse particle size has an augment trend to Jin-lie waterway and Gu-ning-tou. b. Sand on the beach- High, low tidal median grain size in general is given priority to with coarse sand, each station size difference is not big; we have a trend of diminishing from north to south. c. Bed suspended load- Investigating at surf zone station for the first time, and calculating the net rate of between 0.12 ~ 0.88 cm3 / min, the main direction of drift sand transport large extend parallel to the coast or contour is given priority to. Surf zone with inner station net between 1.17 ~ 3.96 cm3 / min, the main direction of drift sand transport in general is given priority to with vertical coastline. A second survey surf zone outside the station, and the calculation of the amount of net transmission rate between 1.83 ~ 9.22 cm3 / min, the main direction of drift sand transport in general is given priority to with vertical coastline. Surf with inner station net transfer between 1.74 ~ 9.47 cm3 / min, the main drift sand transmission direction somewhat parallel to the coast to the southeast. d. Offshore current during the investigation and monitoring of the region mainly the east - west dir., average velocity 10 to 40 cm/s about 82 ~ 83%. Flood tidal current is toward to east and then turn west; ebb tide, give priority to the west and then turn east first. Twice survey of nearshore current to flood, at ebb tide are turning time, the difference about almost 2 ~ 4 hours. Third, Coastline Change One –Dimension modle From 2005 to 2013, a total of eight years, the average amount of coastline back at about 31.52 m, coastal erosion from An-ci to Long-kou is more serious. One-dimensional model with two-dimensional numerical model of wave field simulation results are coastline change during summer and winter. Results show that this project area in only considering season under the action of wind and waves will not have obvious change. Two-dimensional numerical simulation of coastal change In winter wave, summer wave, and 50-year period of ESE and ENE typhoon wave action, the nearshore wave height less than 0.3 m, mostly nearshore current mostly below 0.03 m/s. Topography presents us stable, little change, only Gu-ning-tou and near An-ci vary slightly. Forth,Coast protection strategy Coast protection planning scheme two One, geotextile submerged, geotechnical sand in geotechnical fabric processed into circumference of 4.3 m, height of 0.8 m, a single length is 50 m, bottom bed fortification anti-scouting. Along the Gu-ning-tou to Long-kou at depth of about 1 m laid geotextile submerged, the total length of about 5500 meters. Estimates of the construction funds of about 22.55 million (NTD), maintenance costs about 0.68 million (NTD) a year. Two, to work geotextile submerged with artificial beach nourishment, geotextile layout as one. Estimates of the construction funds of about 46.75 million (NTD), maintenance costs about 1.41 million (NTD) a year.