Chapter 4
Sand dune Analysis of the Study Area
4.1 Introduction:
Researcher analysis sand dunes because a great variety of activities including recreation and recreational developments, a forestation, agriculture, housing and industry, replaces traditional management practices and also knowing the structure of sand dune.
4.2 Definition of Dune
The modern word dune came into English from French cira 1790. In ancient times, words cognate to dune probably had the meaning of a built – up hill or citadel.
A dune is a hill of san built by aeolian processes. Dune occurs in different forms and size, formed by interaction with the wind.
Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most widely distributed dunes are those associated wit coastal regions, the largest complexes of dune are found inland in dry regions and associated with lake or sea beds.
Dunes also form under thee action of water flow, on sand or gravel beds of river, estuaries an the sea bed. (Wikipedia, the free encyclopedia)
Sand dunes occur throughout the world, from coastal and lakes shore palings to arid desert regions. In addition to the remarkable structure and pattern of sand dunes, they also provide habitats for a variety of life which is marvellously adopted to this unique environment sand dune protect include areas from storm surges, hurricane, flood water and wind and wave action that can damage property.
4.3 Dune measurement method:
Among the different methods of measuring the sediment size, pipetle, sieve and hydrometer are the most common and widely used techniques. The sieve method is the mechanical sieving of particles and issued to measure the particle size grater than 63 microns.
The step of sieve method analysis:
The following procedure has been followed to complete this analysis.
Ø At first we took the weight of given sediment with the help of electrical balance.
Ø Than the sediment put down on t sieves and measured.
Ø After measurement the total specimen has been put down on the sieves.
Ø Than the sieves, as a result sharing the different size of particles far on the different sieves.
Ø Then the particles of different sieve have been taken in the separate six pot, before the weight of pot including sample has been measured. It has been found the weight sample by subtraction from he weight of empty pot.
Ø To complete the particle size analysis, some instrument have been used such as Electrical balance, Six sieves, Breish, Pot and Jar.
4.4 Dune data presentation:
4.4.A: Teknaf beach
The samples which have been undertaken for sieve analysis. The data are given below table
Presentation of particle shape data
Site – A
Surface sand dune in Teknaf beach
Table – 4.1 Presentation of particle shape data
| Sta. No. | Height (feet) | Wa% Pebble | Wb% Very Coarse Sand | Wc% Coarse Sand | Wd% Medium Sand | We% Very fine sand | Wf% Silt and Clay | Losses |
| 1 | 5′ 4″ | 0 | 1.2 | 1 | 75.4 | 13.8 | 2.4 | |
| 2 | 5′ 1″ | 0 | 0 | 0 | 71.1 | 2.4 | 24.5 | |
| 3 | 1′ 1″ | 0 | 0 | 0 | 62.9 | 14.2 | 22 | |
| 4 | 7′ | 0 | 0.4 | 0.2 | 55.5 | 0 | 43.4 | |
| 5 | 1′ 4″ | 0 | 0.2 | 0 | 32.3 | 23.7 | 43.1 | |
| 6 | 2′ 3″ | 0.4 | 0.5 | 0 | 29.1 | 23.2 | 46.2 | |
| 7 | 2′ 5″ | 0.5 | 0.3 | 0.2 | 25.3 | 25.5 | 47.6 | |
| 8 | 2′ 5″ | 0 | 1.4 | 0.5 | 28.1 | 20.8 | 48.8 | |
| 9 | 2′ 3″ | 1 | 0.6 | 0.3 | 19.1 | 26.2 | 52.2 | |
| 10 | 2′ 6″ | 0.4 | 0.3 | 0.2 | 23.9 | 26.4 | 48.8 | |
| 11 | 2′ 2″ | 0.7 | 0.4 | 0.2 | 24.6 | 25.1 | 48.5 | |
| 12 | 2′ 5″ | 1.1 | 0.2 | 6.3 | 21.8 | 22.7 | 46.9 | |
| 13 | 2′ 8″ | 1.3 | 0.8 | 0.2 | 14.7 | 18.9 | 62.2 | |
| 14 | 2′ 9″ | 1.6 | 1.1 | 0.5 | 11.1 | 18.4 | 66.1 | |
Source: Laboratory analysis
Description
Particle shapes can be used as signature to the process of erosion, deposition and transportation and also the hydronomic source. Jones et al., 1999 have been recommended that 27 types of particle shapes that reflect grain morphology and the process of transportation, erosion, deposition,
Table 4.1 contains fourteen (14) sediment samples. In this table, say that medium sand, very fine sand, silt and clay are commonly seen. The highest percentage is medium sand 55.5% are situated in 7 feet, the highest very find sand 25.5% are situated in 2 feet 5 inches. The highest silt and clay are situated in 2 feet 9 inches. However, the table clearly shows that medium sand very fine sand and silt and clay are very common in near the coast. Pebble, very coarse sand and coarse sand are found the far way in the coast.
Site – A
1 feet depth sediment in Teknaf beach
Table 4.2: Presentation of particle shape data
| Sta. No. | Height (feet) | Wa% Pebble | Wb% Very Coarse Sand | Wc% Coarse Sand | Wd% Medium Sand | We% Very fine sand | Wf% Silt and Clay | Losses |
| 1 | 1 feet | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 2 | 1 feet | 0 | 0 | 0 | 61.86 | 1.1 | 37.04 | 0 |
| 3 | 1 feet | 0 | 4.5 | 4.5 | 77.66 | 3.2 | 6.1 | 6.44 |
| 4 | 1 feet | 0 | 0 | 0 | 63.5 | 0 | 36 | 0.5 |
| 5 | 1 feet | 0 | 0 | 0 | 24.96 | 23.51 | 51.09 | 1.22 |
| 6 | 1 feet | 0 | 0 | 0 | 33.7 | 26.8 | 39.2 | 0.3 |
| 7 | 1 feet | 0 | 0 | 0 | 42.59 | 29.22 | 17.49 | 1029 |
| 8 | 1 feet | 0 | 0.14 | 0.14 | 21.42 | 23.19 | 54.57 | 0.68 |
| 9 | 1 feet | 0 | 0 | 0 | 22.1 | 25.6 | 51.7 | 0.2 |
| 10 | 1 feet | 0 | 0 | 0 | 13.10 | 31.95 | 51.73 | 3.22 |
| 11 | 1 feet | 0 | 0.2 | 0.2 | 14 | 26.6 | 58.9 | 0.3 |
| 12 | 1 feet | 0 | 0.1 | 0.1 | 12.7 | 21.8 | 53.2 | 12.2 |
| 13 | 1 feet | 0 | 0.1 | 0.1 | 18.1 | 24.4 | 54.6 | 2.5 |
| 14 | 1 feet | 2.2 | 0.6 | 0.6 | 12.2 | 0 | 82.6 | 0.6 |
Source: Laboratory analysis
Description:
Particle shape analysis and to know the characteristics of sand dune in the coastal area is very important for the development of a country. In the table 4.2 medium sand, very fine sand, silt and clay are mostly common in this area and some pebble, very coarse sand, an course sand are found.
4.4B: Teknaf beach: The sample which have been undertaken for sieve analysis. The data are given below table
Site – B
Surface sand dune in Teknaf beach
Table – 4.3: presentation of particle shape data
| Sta. No. | Height (feet) | Wa% Pebble | Wb% Very Coarse Sand | Wc% Coarse Sand | Wd% Medium Sand | We% Very fine sand | Wf% Silt and Clay | Losses |
| 1 | 7′5′′ | 0 | 0 | 0 | 41 | 58.2 | 0 | 0.8 |
| 2 | 4′9′′ | 0 | 0 | 0 | 35.4 | 63.6 | 0 | 1 |
| 3 | 3′2′′ | 0 | 0 | 0 | 10 | 89.6 | 0 | 0.4 |
| 4 | 3′6′′ | 0 | 0 | 0 | 26.2 | 73.6 | 0 | 0.2 |
| 5 | 2′ | 0 | 0 | 0 | 23.4 | 73.8 | 1.2 | 1.6 |
| 6 | 4′ | 0 | 0 | 0 | 0 | 32 | 67.4 | 0.6 |
| 7 | 3′7′′ | 0 | 0 | 0.8 | 57.8 | 38.8 | 0.8 | 1 |
Source: Laboratory analysis
Description:
Table 4.3 contains seven sediment samples and this sediment has been taken from seven station. In the above table, it is say that, medium sand 41% and very fine sand 58.2$ are contains in stations 1. Very fine sand 63.6% are contains in station 2. The highest vet fine sand 89.6% are contains in station 3. The highest very fine sand 73.6%, 73.8%, 32% & 38.8% are contains respectively in station 4, 5, 6 and 7. Medium sand and very fine sand are common in site B (Teknaf beach). Silt and clay are found in station 5, 6 and 7.
Site –B
1 feet depth sediment in Teknaf beach
Table – 4.4: presentation of particle shape data
| Sta. No. | Height (feet) | Wa% Pebble | Wb% Very Coarse Sand | Wc% Coarse Sand | Wd% Medium Sand | We% Very fine sand | Wf% Silt and Clay | Losses |
| 1 | 1 feet | 0 | 0 | 0 | 11.8 | 88 | 0.2 | 1.4 |
| 2 | 1 feet | 0 | 0 | 0 | 0 | 23.4 | 75.2 | 0.82 |
| 3 | 1 feet | 0 | 0 | 0 | 85.6 | 13.59 | 0 | 1 |
| 4 | 1 feet | 0 | 0 | 0 | 37 | 62 | 0 | 0.8 |
| 5 | 1 feet | 0 | 0 | 0 | 28.2 | 71 | 0 | 1.6 |
| 6 | 1 feet | 0 | 0 | 0 | 57.6 | 46.8 | 0 | 0.4 |
| 7 | 1 feet | 0 | 0 | 0 | 83.8 | 15.8 | 0 | |
Source: Laboratory analysis
Description:
Table 4.4 contains seven 1 feet depth sediment samples and this sediment has been taken from seven station. In station 1, very fine sand (88%) is very high; In station 2, Silt and clay percentage is 75.2, In station 3, Medium sand percentage is 85.6%; In station 4, very fine sand percentage is 62; In station 5, very fine sand percentage is 71; In station 6, Medium sand percentage is 51.6 and in station 7, Medium sand percentage is 83.8. So, we can say the medium sand, very fine sand are found in 1 feet depth in Teknaf beach. Some silt and clay found also in station 1 & 2.
4.4C: Shahporir Dwip:
Site – C
Surface sand dune in Shahporir dwip
Table – 4.5: presentation of particle shape data
| Sta. No. | Height (feet) | Wa% Pebble | Wb% Very Coarse Sand | Wc% Coarse Sand | Wd% Medium Sand | We% Very fine sand | Wf% Silt and Clay | Losses |
| 1 | 5′2′′ | 0 | 0 | 0 | 1 | 1.6 | 96.8 | 0.6 |
| 2 | 4′4′′ | 0 | 0 | 0 | 0.6 | 1.6 | 90.8 | 7 |
| 3 | 1′ | 0 | 0 | 0 | 0.8 | 1.4 | 94.2 | 5.6 |
| 4 | 1′2′′ | 0 | 0 | 0 | 0.8 | 1 | 96.2 | 2 |
| 5 | 2′4′′ | 0 | 0 | 0 | 2 | 1.8 | 93.2 | 3 |
| 6 | 1′6′′ | 0 | 0 | 0 | 0.6 | 1.2 | 96.2 | 2 |
| 7 | 3′ | 0 | 0 | 0 | 2 | 2.4 | 95.6 | 0 |
Source: Laboratory analysis
Description
Table 4.5 contains seven surface sediment samples and this sediment has been taken from seven station. From te above table, it is clear that, silt and clay percentage is very high in every station. A few medium sand and very fine sand are found in this site. Any pebble, very coarse sand and coarse sand are found in this site.
Site –B
1 feet depth sediment in Shah Porir Dwip
Table – 4.6: presentation of particle shape data
| Sta. No. | Height (feet) | Wa% Pebble | Wb% Very Coarse Sand | Wc% Coarse Sand | Wd% Medium Sand | We% Very fine sand | Wf% Silt and Clay | Losses |
| 1 | 1 feet | 0 | 0 | 0 | 1.8 | 2.2 | 92.6 | 3.4 |
| 2 | 1 feet | 0 | 0 | 0 | 1.4 | 1.6 | 91.6 | 5.4 |
| 3 | 1 feet | 0 | 0 | 0 | 1.2 | 1.2 | 95.8 | 1.8 |
| 4 | 1 feet | 0 | 0 | 0 | 1.8 | 0.4 | 96 | 1.8 |
| 5 | 1 feet | 0 | 0 | 0 | 2.4 | 1.6 | 93.6 | 2.4 |
| 6 | 1 feet | 0 | 0 | 0 | 1 | 1 | 95.6 | 2.54 |
| 7 | 1 feet | 0 | 0 | 0 | 3 | 3.6 | 93 | 0.4 |
Source: Laboratory analysis
Description
Table 4.6 contains seven 1 feet depth sediment samples and this sediment ahs been taken from seven station. In the above table, it is seeing that, silt and clay percentage is very high in every station. Some medium sand and very fine sand are found in these station. But pebble, very coarse sand and coarse sand are not found in these station.
