人工沙灘養(yǎng)護外文翻譯

1、<p>　　California Beach Restoration Study January 2002</p><p>　　4. NOURISHMENT CONCEPTS</p><p>　　Simply stated, beach nourishment is the introduction of sedimen

2、t onto a beach. In most cases, the sediment is sand and the beach is in an eroded condition. The process supplements the diminishing supply of natural sediment. Nourished shorelines provide two primary benefits: increase

3、d area for recreation, and greater protection against coastal storms. Other tangible benefits include tourism revenues, restored wildlife habitats, enhanced public health and safety, increased coastal access, and redu<

4、;/p><p>　　Sediment characteristics and sources, sediment placement methods, and maintenance</p><p>　　Requirements, the key components of nourishment projects, are discussed in the following section

5、s.</p><p>　　4.1 Overview</p><p>　　Whereas structural means of beach retention were common 30 to 50 years ago, beach</p><p>　　Nourishment has become the preferred method in recent de

6、cades. Beach nourishment represents a “soft” method of shoreline stabilization, in contrast to “hard” alternatives such as groins. Hard structures are designed to remain stable and stationary, fully resisting the actions

7、 of waves, currents, and sediment transport. Hence, they tend to be large structures and may significantly impact the natural movement of sand. Soft stabilization alternatives, such as sand or cobble beach fills, mimic n

8、atur</p><p>　　seasonal shoreline fluctuation remains within acceptable limits during the project design life.</p><p>　　Ultimately, however, nourishment material is sacrificial in nature and will

9、 require periodic maintenance.</p><p>　　Introducing new sand onto the beach can compensate for a reduced sediment supply delivered by rivers and streams. In this way, beach nourishment represents a means of

10、restoring a more natural system. Wider beaches, in turn, reduce the need for hard structures while simultaneously increasing recreational opportunities.</p><p>　　4.2 Beach Nourishment Material</p><

11、;p>　　The characteristics of the available fill material are of utmost importance in the design of beach nourishment projects. At a minimum, the sediment must be uncontaminated and have a small fraction of fine grain s

12、izes (“fines”, such as silt and clay). Most nourishment projects use sand as the fill material, although projects have been implemented using pebbles and cobbles.</p><p>　　In addition to the foregoing proper

13、ties, the fill material should possess grain sizes that are comparable to or larger than those of the native beach sand. Comparably sized grains will tend to behave in a manner analogous to that of the native material, w

14、hile larger grain size will tend to be more stable. Smaller grains should be avoided whenever possible, as they are less stable and hence prone to accelerated erosion.</p><p>　　4.3 Sediment Sources</p>

15、<p>　　Sources of nourishment material may include offshore deposits, inland areas, sediment accumulations from within the littoral system, and “sand of opportunity” (NRC, 1995). Each of these sources is described

16、in one of the sections that follow.</p><p>　　4.3.1 Sand of Opportunity</p><p>　　The majority of beach nourishment projects conducted in California have utilized “sand of opportunity”, which is d

17、erived from projects whose primary motive is not beach replenishment. Common sources of this material have been dredged sediment from harbor construction, harbor maintenance, and lagoon restoration projects (Wiegel, 1994

18、). In these cases, the suitability of the sediment as a beach fill material must be carefully examined both in terms of size fraction and pollutants. The primary adva</p><p>　　4.3.2 Offshore Sources</p>

19、;<p>　　During recent decades, offshore sand deposits have served as the most common source of borrow material. Sand from these relict deposits is typically dredged and placed on the dry beach. The primary advantag

20、es of this approach include low cost, high placement rates on the receiving beach, and minimal disturbance onshore while the project is underway.</p><p>　　Although the use of offshore sand deposits also has

21、disadvantages, careful planning and coordination with resource and regulatory agencies can minimize the potential drawbacks. One such drawback is the tendency for offshore sediments to contain a higher percentage of silt

22、 and clay, necessitating a large overfill volume to account for anticipated losses. Additionally, the offshore borrow areas must be sited well seaward of the active portion of the beach profile so that the nourishment sa

23、nd is no</p><p>　　4.3.3 Inland Sources</p><p>　　There are a number of inland sources of beach-quality sand. In southern California, the loss of sediment reaching the coast due to the damming of

24、rivers is a well-documented phenomenon (Chapter 7, this report). The sediment trapped behind the dams represents a significant source of nourishment material. The use of this sediment accomplishes two objectives: re-esta

25、blishment of the reservoir capacity and nourishment of the beaches. Other inland sources that have been exploited in the past include </p><p>　　4.3.4 Sources within the Littoral System</p><p>　　

26、Sand bypassing and backpassing operations redistribute sand within the littoral system. Neither method represents a true source of sand because no new material is added to the system.</p><p>　　However, both

27、operations have been utilized extensively in California to place sand where it is most needed.</p><p>　　Sand bypassing is the practice of transporting accumulated sand from the upcoast side of a sediment bar

28、rier, such as a jetty, to the eroded side. The process attempts to restore the natural downcoast flow of sand. Many harbors in California conduct sand bypassing in conjunction with maintenance dredging operations.</p&

29、gt;<p>　　Sand backpassing involves the mechanical transport of material from a wide stable beach to an upcoast sediment-starved beach. This method often is utilized in locations where the sand from an eroding reac

30、h moves alongshore and is deposited in a more sheltered area. Backpassing essentially “recycles” the sand back to the eroding beach. If the sand volumes are moderate and the haul distances are short, the practice can pro

31、vide a cost-effective scheme for beach maintenance. Similar to sand bypassin</p><p>　　4.4 Beach Fill Placement</p><p>　　Once sand is placed on the beach, waves and currents redistribute the mate

32、rial offshore and alongshore until a stable configuration is achieved. Depending on local conditions, a nourished beach may take several months or years to reach the equilibrium condition. The fill may be placed well abo

33、ve the shoreline as dune nourishment, on the dry beach and near the waterline, across an extended portion of the profile that stretches from the dry beach to well offshore, or completely offshore as a sand </p>&l

34、t;p>　　4.4.1 Dune Nourishment</p><p>　　Dune nourishment (Figure 4.1) is particularly effective in protecting upland development against storm waves. The placement of material high above the waterline does

35、not expand the width of the dry beach, however, and therefore is not appropriate when the enhancement of recreational opportunities is an important project objective.</p><p>　　Figure 4.1 Dune nourishment<

36、/p><p>　　4.4.2 Dry Beach Nourishment</p><p>　　Nourishment of the dry beach is a very common approach. In this scheme, sand is placed on the dry portion of the beach and near the waterline, and resu

37、lts in an immediate increase in beach width available for recreation (Figure 4.2). However, because no sand is placed on the submerged portion of the beach, sand will be redistributed offshore across the entire profile u

38、ntil a stable configuration is established. The equilibrating process results in a substantial narrowing of the initial dry beach</p><p>　　Figure 4.2 Dry beach nourishment</p><p>　　4.4.3 Profile

39、 Nourishment</p><p>　　Profile nourishment involves placing the sand across the entire beach cross-section, both above and below water (Figure 4.3). The placement method attempts to build the beach in an alre

40、ady stable configuration. Because the equilibrium condition develops immediately, there is little offshore redistribution of sand and changes in the dry beach width are minimal. However, this placement scheme is more dif

41、ficult and also provides less storm protection because there is no extra reserve of sand on the</p><p>　　Figure 4.3 Profile nourishment</p><p>　　4.4.4 Nearshore Bar Nourishment</p><p&

42、gt;　　This method involves the placement of beach fill material in a sand bar just offshore of the surf zone (Figure 4.4). To be successful, the placement must be within the active portion of the beach profile. The sand w

43、ill gradually move onshore under the influence of waves and currents, increasing the beach width. The period of time required for the sediment to be moved up onto the beach varies with wave conditions. Although the nears

44、hore bar placement scheme is the most technically challenging, it</p><p>　　Figure 4.4 Nearshore bar nourishment</p><p>　　4.4.5 Beach Nourishment with Sand Retention Devices</p><p>　

45、　Sand retention devices are often used to prolong the effectiveness of a beach nourishment program (USACE, 1995). These devices are designed to reduce the amount of fill lost alongshore or offshore. Examples of natural s

46、and containment are common in California. Many naturally wide beaches exist where sand is retained by sediment-blocking features such as headlands, reefs, rocky stream deltas, and other irregular bottom contours (Everts,

47、 2000). In concept, the use of sand retention devices with no</p><p>　　4.5 Maintenance</p><p>　　As indicated at the outset of this chapter, nourished beaches typically require periodic</p>

48、<p>　　replenishment. Waves and currents will redistribute the beach fill sand in the alongshore and cross-shore directions, background erosion may persist, and extreme storm events may cause large losses of sedime

49、nt from the dry beach. As a result, maintenance should be scheduled in the original project plan and monitoring should be performed to insure that the maintenance schedule is appropriate. Typical re-nourishment intervals

50、 range between two and ten years.</p><p>　　Depending on local site conditions and sediment availability, it may be more economical to place a smaller fill initially and perform frequent re-nourishment. Conve

51、rsely, if the beach fill project is dependent on a single large dredge project in a nearby navigation channel, then a larger initial fill will be placed and the interval between maintenance operations will be greater.<

52、;/p><p>　　4.6 References</p><p>　　Everts, C. H., and C. Eldon, 2000. “Beach Retention Structures and Wide Sandy </p><p>　　Beaches inSouthern California”, Shore & Beach, Vol.68, No.

53、 3, pp. 11-22.</p><p>　　National Research Council, 1995. Beach Nourishment and Protection, Washington D.C.:National Academy Press, 334 pp.</p><p>　　U.S. Army Corps of Engineers, 1995. Design of

54、Beach Fills, USACE Engineering Manual1110-2-3301, 86 pp. + appen.</p><p>　　Wiegel, R.L., 1994. “Ocean Beach Nourishment on the USA Pacific Coast”, Shore & Beach,Vol. 62, No. 1, pp. 11-35.</p><

55、p><b>　　中文翻譯：</b></p><p><b>　　4.人工養(yǎng)護理念</b></p><p>　　簡單來說，海灘養(yǎng)護就是將其他地方的沙補充到沙灘上。在大多數情況下，泥沙是沙和海灘處于侵蝕條件下的產物。而這個過程彌補了天然泥沙供給的減少。采用人工海灘養(yǎng)護的海岸線有兩個主要的好處：擴大了娛樂場所的區(qū)域和增強抵抗海岸風暴能力。另外直接

56、的好處包括增加旅游業(yè)收入，恢復野生生物棲息地，增強公共健康和安全，增加海岸的活動范圍和減少剛性水工建筑物。</p><p>　　泥沙的特性、來源、放置方法和維護要求，這些關鍵的人工海灘養(yǎng)護部分，將會在下面的章節(jié)中討論。</p><p><b>　　4.1.概況</b></p><p>　　在三十到五十年前，利用結構性建筑物來保護海灘是很普遍的，

57、然而，在近幾十年來，人工海灘養(yǎng)護的方法已經很受歡迎。</p><p>　　人工沙灘養(yǎng)護代表著一種穩(wěn)定海岸線的軟性治理方法，與其相對的是剛性方法，如堤壩。剛性的建筑物設計是用來保持海灘的穩(wěn)定、不變，以便足以抵抗波浪、流和泥沙輸運的作用。因此，這些建筑物盡量做得足夠大，可以抵抗天然的泥沙運動。軟性的穩(wěn)定方法，如沙子或者往海灘填充卵石，來模擬自然運動，希望變得有活力，來應對波浪、流作用下而產生的變化。對于用沙子來進行人

58、工海灘養(yǎng)護而言，在冬季期間干燥的海灘面變得狹窄，然后在狂野的夏季波浪條件下干燥的海灘面會恢復到原先的大部分或者全部寬度。</p><p>　　理論上來講，人工海灘養(yǎng)護項目的設計是為海岸線波動在設計生命周期內保持合理的范圍內。然而，最后海灘養(yǎng)護物質在自然情況下的消耗需要周期性維護補充。</p><p>　　往海灘引進新的沙子能夠補充在河流、溪流作用下流失的泥沙減少量。通過這個方式，人工海灘養(yǎng)

59、護代表著一種恢復得更加自然化的體系。相應地，更多寬闊海灘減少對剛性建筑物的需求，然而，同時增加娛樂的可能性。</p><p>　　4.2.人工海灘養(yǎng)護的物質</p><p>　　可用于填充的養(yǎng)護物質特性在設計人工海灘養(yǎng)護項目中是至關重要的。至少，泥沙必須是不受污染的，允許一小部分細小顆粒（如淤泥、黏土顆粒等）雖然項目已經用卵石或者鵝卵石作為填充物，但是大部分海灘養(yǎng)護項目采用的是沙子作為填充

60、物質。</p><p>　　除了前灘地以外，填充物應該擁有的顆粒尺寸能夠比得上或大于當地海灘的沙子尺寸。尺寸可以比較的顆粒傾向與當地物質類似的運動方式，然而，更大的顆粒會傾向于更加穩(wěn)定。無論何時，更小的顆粒都應避免，因為這些小顆粒不穩(wěn)定，會傾向于加快其侵蝕速度。</p><p><b>　　4.3.泥沙的來源</b></p><p>　　養(yǎng)護物

61、質的來源可能包括近海沉積物、內陸區(qū)域、源于海濱系統內的“泥沙隨機性”累積。（NRC，1995）。每個泥沙來源會在下面的章節(jié)中描述。</p><p>　　4.3.1.運動中沙子的隨機性</p><p>　　在吉利福尼亞州所進行的大部分海灘養(yǎng)護項目都應用了運動中沙子的隨機性這一特性，這源于那些主要不是以海灘沙子補充為動力的自然海灘演變規(guī)律。這種物質的普遍來源于港口建設、港口維護和瀉湖的恢復項目

62、中的泥沙疏浚（Wiegel，1994）。在這些案例當中，作為合適的海灘填充物質必須要經過一系列的顆粒尺寸、污染物質的認真檢驗符合。運動中沙子的隨機行的主要優(yōu)勢是低成本。通過在海灘放置泥沙，海水里沉積物的成本被排除在外，還有海灘養(yǎng)護項目能夠從疏浚作業(yè)中獲得實在的效益。</p><p>　　4.3.2.近海物質來源地</p><p>　　近幾十年間，海沙沉積物已經作為最常見的輸出物質來源。來源

63、于殘積物的沙子被疏浚和放置在干燥的海灘上。而這個方案的主要好處有低成本、在物質輸入區(qū)的海灘上高的沉積率，當這個項目在進行中，物質輸運的距離是最小的。雖然海洋沉積物也有其缺點，但認真的規(guī)劃以及適當的媒介協調，就能夠使?jié)撛诘娜秉c最小化。其中，有這樣一個缺點是傾向于海里的泥沙含淤泥、黏土的比重比較高，需要溢出量大才能達到補充預期泥沙流失量。</p><p>　　此外，海上泥沙輸出區(qū)域必須位于正面朝向岸灘輪廓最活躍部分，

64、以便養(yǎng)護的沙子沒有讓波浪、流作用排回到輸出區(qū)。</p><p>　　4.3.3.內陸物質來源</p><p>　　有大量的海灘質沙子來源于內陸物質。在加利福尼亞州南部，流失的泥沙到達海岸取決于在河流建堤壩，這個現象就好比如一份很好的備份文件證明。困在大壩后面的泥沙代表著一種極其重要的養(yǎng)護物質來源。這種泥沙的使用能夠達到兩個目的：能夠重建儲存庫容，海灘的養(yǎng)護物質。另外那些過去已經被利用的內陸

65、物質來源包括沙丘、荒地。</p><p>　　4.3.4.在海濱系統內的物質來源</p><p>　　沙子沖刷和淤積，這些作用在海濱系統內重新分配。既不是一種方法能代表著一種真正的沙子來源，也不是因為一種新的物質添加到系統中。然而，這兩種沖刷和淤積的作用原理已經廣泛地應用到及利福尼亞州最需要填沙的地方了。</p><p>　　沙子的沖刷就是來自上行海岸邊的沙擋被搬運

66、到已經侵蝕的海岸。而這個過程試圖去恢復那自然狀況的下行海岸沙流。在及利福尼亞州很多港口都與疏浚作用聯系起來引導沙子的輸運。</p><p>　　沙子的回淤是關于來自一個廣闊穩(wěn)定海灘的物質機械化地輸運到上行海岸缺少泥沙的海灘上。這種方法經常應用于來自侵蝕區(qū)域的沙子沿著海邊運動，最后在一個更受庇護的區(qū)域沉積下來。</p><p>　　從本質上來講，回淤可重新地將沙子輸運回到受侵蝕的海灘上。如果

67、沙子的體積適中，加上被輸運的距離短，那么這種情況能夠提供一個更為節(jié)省海灘維護的成本方案。與沙的沖涮相似，這個操作過程要在正常的基礎上引導進行。</p><p>　　4.4.海灘填充物的放置</p><p>　　一旦沙子放置到海灘上，海浪和流會重新分配這些物質到海里和周邊的海岸上，直到一個穩(wěn)定的組合形成。養(yǎng)護一片海灘可能要花上幾個月或者數年去達到一個平衡狀態(tài)，這取決于當地的實際情況。<

68、/p><p>　　那填充物可能會正好放置在海岸線上作為沙丘的養(yǎng)護物質，在干燥的海灘上和還參與海水的分界線附近，橫跨一個干燥的海灘面延伸到，恰好與海水接觸的輪廓面，或者作為海里的一個沙壩。在某些情況下，剛性建筑物可能延長養(yǎng)護物的生命期限。多種不同的放置策略將會在下面討論。</p><p>　　4.4.1.沙丘養(yǎng)護</p><p>　　沙丘養(yǎng)護對于保護抵抗風浪的高地發(fā)展，是

69、特別有效的。然而，在分水線正上方高處的物質放置，沒有延伸到干燥的海灘面的寬度。因此，當增加海灘面積的娛樂可能性是非常重要的項目目標時，是不適合的。</p><p>　　4.4.2.干燥的海灘養(yǎng)護</p><p>　　干燥的海灘養(yǎng)護是一個非常普遍的方案。在這個計劃中，沙子放置到海灘面干燥的部分和分水線附近，會迅速增加娛樂的可用海灘面寬度。然而，因為在沒有沙子放置下的海灘水下部分，沙子將會在海

70、里重新分配到海灘的整個輪廓面范圍，直到穩(wěn)定的海灘組合建立完成。這個平衡過程將會導致起初海灘面寬度的大面積減少。</p><p>　　海灘面上流失的沙子，有時變化相當快，在過去已經成為海灘養(yǎng)護物質的主要來源爭議之處。受過良好公共教育的海岸工程師、科學家、設計者排除了對填充沙子重新分配的錯誤理解。應該要明確認識到沙子會適應更加穩(wěn)定的海灘組合，這導致大面積縮窄原先海灘面的寬度。然而，這個項目的設計是為了當沙子重新被波浪

71、、流作用后，提供我們想要的海灘面寬度，更窄的設計寬度應該是公共所期望結果。</p><p>　　4.4.3.海灘輪廓養(yǎng)護</p><p>　　海灘輪廓養(yǎng)護包括在全部海灘的橫斷面都填充沙子，同時包括水上部分和水下部分。這種填充沙子的方法試圖在已經穩(wěn)定的原海灘組合下去建立新的組合。因為平衡狀況變化迅速，海灘上的沙子也會迅速重新分配，最后穩(wěn)定下來。因此，干燥的海灘寬度的變化是最小的，穩(wěn)定的。然而

72、，這填充計劃顯得更加困難，還有，也提供不了那么多抵抗風暴的防護。因為海灘上沒有其它可用的沙子作為沙丘和干燥海灘養(yǎng)護物質。</p><p>　　4.4.4.附近海岸沙壩養(yǎng)護</p><p>　　這個方法是關于填充在沙壩與破波帶范圍內的海灘養(yǎng)護物質。為了取得成效，填充物必須在海灘輪廓活躍部分范圍內。沙子會慢慢地在波浪、流的作用下，移向岸上，結果增加了海灘面的寬度。這個時間周期要求泥沙運動到受多

73、種波浪條件作用的海灘上。盡管附近海岸沙壩填充計劃是最有技術性上的挑戰(zhàn)，這可能是最節(jié)省成本的方案。</p><p>　　4.4.5.用保沙的設計進行海灘養(yǎng)護</p><p>　　保沙的設計常應用于延長海灘養(yǎng)護項目的持久性影響。這些設計是為了減少海岸邊上或者海底里的填充物數量。例如天然沙污染物在加利福尼亞海岸是很常見的。很多天然寬闊的海灘都存在這個問題，在那里沙子被沙擋結構物留住，如這些結構物

74、有岬角、珊瑚、巖石性河流三角洲，還有其它不規(guī)則的地形輪廓底部。理論上來講，使用沙子保留設計養(yǎng)護是吸引人的，然而，應該謹慎考慮。負面的影響，包括加速相鄰下行海岸沙灘的侵蝕和如果這些設計沒有適當利用，附近海灘面娛樂可能性的丟失就會發(fā)生。</p><p><b>　　4.5.維護</b></p><p>　　在這個章節(jié)的開端部分就提到，受養(yǎng)護的海灘通常要求周期性的物質填充。

75、波浪和流將會重新分配海灘填充物在海岸邊、斜交海岸方向和侵蝕背景下的沙子會繼續(xù)存留，還有極端的風暴會引起干燥海灘的泥沙大量損失。因此，維護應該在原先的項目規(guī)劃中作好計劃和監(jiān)督，應該執(zhí)行以確保維護計劃是合理的。通常二次養(yǎng)護期是在兩到十年之間。</p><p>　　由于當地地理位置情況和泥沙的可利用性，開始填一種比較細的物質和經常進行二次養(yǎng)護可能是更加經濟。相反地，如果海灘填充物項目是依賴于附近海上運輸渠道的疏浚項目，

76、那么大量的填充物將會填充和維護操作之間的范圍將會變得更大。</p><p><b>　　4.6.引用文獻</b></p><p>　　Everts, C. H., and C. Eldon, 2000. “Beach Retention Structures and Wide Sandy </p><p>　　Beaches inSouther

77、n California”, Shore & Beach, Vol.68, No. 3, pp. 11-22.</p><p>　　National Research Council, 1995. Beach Nourishment and Protection, Washington D.C.:National Academy Press, 334 pp.</p><p>　　U

78、.S. Army Corps of Engineers, 1995. Design of Beach Fills, USACE Engineering Manual1110-2-3301, 86 pp. + appen.</p><p>　　Wiegel, R.L., 1994. “Ocean Beach Nourishment on the USA Pacific Coast”, Shore & Bea