Inshore Zone Research Articles

Imbricate Structure in Essex Offshore Shell Banks

VARIOUS shell bodies exist in the chenier plain facies of east Essex1,2. Offshore banks are one of the more prominent types, and within these banks there is often a pronounced vertical imbrication in the surface layer of shells (Fig. 1). This exerts a stabilizing influence on the movement of the shells and shell bodies retarding, though not preventing, long term migration. Imbrication has not yet been observed in deposits of the inshore zone.

Artificial beach as an experimental type of reservoir bank protection

1. Observations over three years have shown that the artificial beach effectively protects the bank of the reservoir against erosion. 2. Owing to the concave shape of the beach shoreline, its individual sections are dissimilar with respect to stability. The straight section has the greatest stability. 3. The angles of inclination of the artificial beach, adopted on the basis of those on natural shoals, are most acceptable for such bank protection. 4. Under conditions of a steady regime of wave action on the reservoir, the stability of the underwater shoals depends not so much on the parameters of the waves as on certain nonwave factors, particularly the regime of water level fluctuations during the navigation season. 5. The artificial bank-protecting beach on the Novosibirsk Hydroelectric Power Plant reservoir is essentially experimental. Results of stability investigation indicate the need for broadening such works in order to select the optimal method of reinforcing banks when using the inshore zone of artificial bodies of water for national-economic purposes.

Feeding Habits of the Squid, Illex illecebrosus

OBSERVATIONS have occasionally been made on the method of attack on prey by Illex in the inshore zone where it feeds mainly on small fishes1–3. This communication suggests a way in which the squid is able to capture smaller food organisms—mainly small crustaceans (Euphausiids)4—when it is schooling in the offshore zone.

On the quantity of allochthonous pollen and spores received by the Rybinsk Reservoir

1. The Rybinsk Reservoir receives about 6 kg of pollen and spores per ha annually ( after date obtained for the inshore zone at Borok in 1959). 2. There are two peaks in the quantity of pollen and spores — in the beginning of May (mainly Betula pollen) and in the first half of October (mainly fungal spores; see the figure). 3. Allochthonous pollen and spores in water bodies may constitute a food resource for aquatic animals, mainly a sourse of vitamines for aquatic animals.

SEDIMENT MOVEMENT AT INDIAN PORTS

India has a large coastline being bounded on three sides by water* On the vest side, the coastline faces the Arabian Sea. Similarly the coastline on the east side is bounded by the Bay of Bengal* The Indian ocean separates the Arabian Sea and the Bay of Bengal at the southern-most end of the coastline (Fig* 1] Since the last IS years, there have been proposals from time to time to establish new harbours or Improve existing harbours or save vast lengths of coastal strips from erosion by wave action In evaluating the merits and de-merits of the sites, a study of the coastal sediment movement is Important since what may be beneficial to a harbour may be harmful for preservation of a coastal strip* Defective planning may cause the loss of the entire shoreline and or the complete blocking of the harbour areas* Improper use of protective structures such as seawalls. breakwatersf groins, jetties etc* will not only be unscientific and uneconomical but accelerate the changes along the shoreline rather than stop them.
 The frequent or long-term changes In shoreline, beach, offshore zone, inshore zone, under ground bars, spits, lagoons, tombolas and similar characteristics of the coastline have significant meanings regarding the sediment motion at the coastline* Hith respect to sediment available for motion, the shor< may be a source, a drain, ovemourlshed, undernourished, sufficiently nourished (Per Bruun, 1955), or a physiographic unit (Mason, 1950). With each type, coastal works will be dlfferent for shoreline improvement and for harbour maintenance. Erosion and accretion by natural processes extend upto offshore zones while with man-made structures, erosion will always start in th< inshore and foreshore zones of the shallow water area. This distinguishing feature in the changes of a shoreline will be a good and reliable preliminary check to determine the type of erosion* Having classified a shoreline according to its sediment nourishment and as a source or a drain, the type of coastal rotection may be selected tentatively. The selected works may then he studied by model techniques. If the premilinary analysis was complete and accurate, the tentatively selected type of coastal work will be found to be most satisfactory thereby saving unnecessary waste of time and money from testing various types of works by model analysis* This method of analysis will be found to be extremely useful in many countries where investigations of the coastlines are far from adequate* Analysis of the changes at existing coastal structures along the coastline and the interpretations of the results as outlined above will be the most satisfactory method* The coastline of India may also be Interpreted similarly in relation to erosion, accretion, and transportation of sediment from the data available from existing structures, harbours and coastal strips, and divided into arbitrary overnourished, sufficiently nourished and undernourished strips and classified as sources or drains as far as possible so that various suitable types of coastal protective structures may be suggested* Indian coastline as a preliminary step may be divided into the West coast facing the Arabian Sea and the East coast facing the Bay of Bengal since the characteristic features of both the coastlines are entirely of different nature with respect to the wind forces, erosion, accretion, and littoral drift along them.