SECTION 2. PHYSICAL AND GEOGRAPHICAL COASTAL PROFILE

2.9. The dynamics and the conditions of the steadiness of the coasts.

2.9.1. The conditions of the steadiness of the coasts.

The most important conditions defining the condition and steadiness of the coasts on the Caspian coast of Russia are [16]:

1. The position of the sea and the tendencies to the changes.

2. The energy of roughness and other hydro-litho-dynamic processes and the movement of pileups, bound with it.

3. The balance of the pileups of the coastal area of the sea and, first of all, the balance of the pileups of the beach and geological and lithological construction of the submarine coastal slope.

4. Anthropogenic effect onto the coast, expressed in different forms (coastal-marine hydro-technical constructions, withdrawals and fills of the pileups, physical and chemical effects onto the coastal biota, and others).

5. Below the attempt to estimate the temporary tendencies of the natural development of the conditions, defining the steadiness of Caspian coasts within the borders of Russia and the possibilities to artificially effect them are taken.

The level changes define the removal of the border of the coastal line. The raising of the level leads to the stepping away from the coast line. The role of geomorphologic conditions is huge: the less the bents are, the more the stepping back is. During the modern raising of the level (form 1978) for about 10-20 cm per year on the coasts of Dagestan the stepping back happens with the speed 10-20 m/year. The same speeds of the level raising lead to the stepping back of the coast line for 100-1000 m/year on the shoal coasts of Kalmikiya and Volga delta.

In accordance with the short term forecast the raising of the level will be reaching the mark of –25 slowly, but steadily. The continued washout of the coasts and their passive flooding without any visible decrease of the speed of the land loss will correspond this process.

One should note that even in the conditions of the stabilization of the sea level the stepping of the coasts back would continue for at least first 20-30 years and accordingly the problems of the steadiness of the coasts will remain open.

The energy of the roughness participates in the washout of the coasts, increasing the passive flood of the land, and the alongshore component of the flow of the wave energy along with the geological and lithological and geomorphologic conditions, defines the objects of the annual alongshore movement of the washouts.

The firmness of the native beds (mainly of the limestone and sand of sarmat) is quite strong, and the speed of their abrasion can be considered independent from the effect of waves (the speed of abrasion is millimeters per year). The effect of waves onto the mellow beds is more significant. Depending on the bigness and content the movement of the pileups can happen in different directions – up and down the beach profile and the submarine coastal slope. In the conditions of Dagestan fruitful conditions for existence of Bentoce organisms appear when there is a cast spread of exits of native beds in the shallow areas. As a result of this the big pieces of the shells, after they die, are thrown out onto the beach, filling up the reserves of its pileups, and after the shell detritus is grinded by the roughness it is moved to the submarine slope. Roughness is the necessary condition for the possibility of such a mechanism. One should mind the fast grinding of the shell material, which is the tens of per cents annually of the original volume.

The space changes of the alongshore component of the wave energy, by means of which the bigness of the container of the alongshore flow of pileups is regulated and the gradients of which define the appearance of the washout and of the accumulation on separate sections of the coast, are even more significant.

More accurate estimations of the part period let to make a conclusion about the fact that the container of the alongshore flow of pileups from the south to the north (from Derbent to the distal of the Agrakhan spit) decreases from 400 to 200 thousand cubic meters/year, living through local changes. Along with that the calculations allowed to confirm the general direction of the alongshore transport to the big parts of the sea coasts of Dagestan and to localize six sections of the cut off of the alongshore movement of pileups, the two of which are stipulated by the protective rollers of Caspiysk and Makhachkala ports. (picture 2.9.1.1).

So, any seaside-sea coastal defensive construction, that is on the way of the transport of pileups along the shores would result the lowering washout.

When continuing the raising of the sea level the coastal system of Dagestan would fall into small litho-dynamic sub-systems, which would develop independently from one another.

Picture 2.9.1.1. The distribution of the parameters of the container of the alongshore flow of the pileups (Ðàñïðåäåëåíèå âåëè÷èí åìêîñòè âäîëüáåðåãîâîãî ïîòîêà íàíîñîâ ( 10⁵ m³/year) along the Dagestan coast.[16].

2.9.2. The sources of the pileups of the coastal area of the sea and the litho-dynamic processes.

Within the limits of the Russian coast of the Caspian Sea there are four big sources of the terrigenous material – the flow of Samur, Sulak, Terek and Volga rivers. There is a row of comparably small rivers bringing he pileups onto the shores, but their role in the feeding of the coasts by the sedimentary material is comparably minimal.

The hard flow of Samur river was about 7,6 million tons a year in the near past. However, due to the hydro-technical regulation of last decades it has significantly decreased and according to some estimations it is not more than 4,7 million tons a year.

13,5 million tons annually would arrive into the delta of Sulak before the construction of Chirkey Hydro Electrical Station (1974), and after the completion of the construction it decreased to 1,64 million tons a year.

About 3 million tons a year arrive into the new delta of Terek. The flow of pileups of Volga river is estimated in the period till 1995 as 15 millions tons a year, and after 1961 it is 13,6 millions tons a year.

The temporary tendency of arrival of pileups onto the coastal area is crearly unsatisfactory and is characterized by significant decrease of the flow of the alluvial pileups.

70-90 % of the beach forming pileups on the most of Dagestan coasts are represented by the biogenic shell and detritus–shell material.

The shell material gets grinded very quickly and that why is drowns fast, being taken out of the balance system of the beach.

The past years the economic activity of a human plays more significant role in the balance of pileups. It effects not only the withdrawal of the pileups from the modern beaches, deepwater work on the lines of approaching channels, but also the replenishment of pileup reserves at separate sections, and the bringing in of artificial materials. Besides, during the raising of the level adversely affect also the previously done developments of the beach sands within the limits of the terrace complexes.

Significant loses of the beach forming material happen during ash processes. At the same time the direction of their activity is not positive, if to take the prevailing of strong winds from the sea side.

Quaternary effect onto the coasts is illustrates by the effects that are received after the construction of rollers of Caspiysk and Makhachkala ports. During the developed and quite powerful longstanding service the sections of accumulation appeared to the south from the coastal constructions and to the north from them the sections of the lower washouts appeared. The instructive example of the longstanding service of these constructions is that any of those constructions, obstructing the alongshore transport of pileups would lead to the similar consequences.

Even when building the waver damping wall that was supposed to save the beach in Derbent, technological reasons and the raising of the sea level led to the washout of the beach from both sides of the built construction, behind of which a swamped lowing appeared.

In the conditions of the intensive stepping back of the coast on some of suburban territories the coast defensive actions, including the clod leading and even the constructions of multiple row groove walls were realized into life. You cannot visible observe the positive effect they give, but still they fully exclude the coasts from the sphere of the recreational use.

Unequal arrival of pileups onto the shore within the limits of Dagestan, as well as the common deficit of pileups and unlucky attempts to use traditional methods of coast strengthening with the help of reinforced concrete constructions induce the necessity to convert to the new strategy of coast defense and to the increase of resources providing the steadiness of coasts. The main element of the new strategy is the conversion to the artificial feeding of the coasts by the pileups first of all on the sections living through sharp deficit of them and introducing the economically deepest interest [16].

The emphasizing of the sections of the coastal feeding by the pileups, methods, volumes and regularity of feeding processes as well as the search of sources of pileups should be recognized as the most important among the complexes of the problems of Caspian Sea.

At the same time before making such a responsible step forward it is necessary to proceed quite a detailed division to regions of sea coasts, taking into account the main components of their dynamics. The division to the regions must be useful also for the preventive estimation of consequences of different actions taken to build ports, coast defenses, including the artificial feeding by pileups and in order to exclude possible negative results.

Due to the fact that the coast strengthening is advised to lead in the frames of one litho-dynamic system, in order to avoid the effect onto the adjacent sections of the coast, let us have a look at the balance division to the regions of the Russian coasts of the Caspian Sea, based on the allocation of autonomous litho-dynamic [16].

Thee division onto the regions of such kind is necessary not only because of the coast strengthening purposes. One should note that the borders of the litho-dynamic systems mainly define the borders of the movement of feed materials as well as the pollution of their sources and this way they represent the overall geo-ecological interest.

The autonomous litho-dynamic system is defined here as a section of the coastal area, within the limits of which the balance of pileups is quite independent from the balance of pileups of adjacent sections of the coast. The tool for the definition of borders of the litho-dynamic system is the calculation of alongshore movement of pileups, based on the data about the original boundary of the coasts and of the roughness for quite long term time interval (not less than 11 years, by means of which the regime statistical steadiness of wave characteristics is defined). The litho-dynamic system is defined as the oblast of contrary alongshore movement of the pileups of convergence of the flow of pileups or the oblast of insignificant alongshore transport.

The program supply, allowing to calculate the potential parameters of the expenses of the alongshore flow of pileups on the basis of regime observations of the roughness and the automated construction of the corresponding graphics, was created at the chair of geomorphologic of the geographic faculty of the Moscow State University.

The computer technology allowed to make also the calculations of the direction and relative volumes of the alongshore movement of pileups and allocate some autonomous litho-dynamic system within the borders of Dagestan. Let us shortly name them and note some additional proves of the reality of their existence.

From south to north there are the following autonomous litho-dynamic systems (picture 2.9.3.1, table 2.9.3.1).

1. Derbent system with the borders from the mouth of Samur to Burun settlement with the length along the shore 100 km.

2. Manasskaya system with the borders from Burun settlement to Catun settlement, long as 31 km.

3. Caspisko-Makhachkala system is long as 57 km with the borders from Satun settlement to Sulak mouth. This autonomous litho-dynamic system is divided into three subsystems due to the man-caused constructions – the defensive rollers of ports of Caspiysk and Makhachkala: a) from Satun settlement to the south roller of Caspiysk port – 3,5km; b) from the north roller of Caspiysk port to the south roller of Makhachkala port – 16 km; c) from the south port of Makhachkala post to the mouth of Sulak – 30 km. Of course, when proceeding the division into the micro regions the systems of internal defined areas of water of Caspiysk and Makhachkala ports must also be allocated. The length of the systems of internal defined areas of water is 7,5 km, however, due to the fact that they are not potential objects of the shore strengthening works and because they are not not very long along the shore, they are not looked at here. On the section of Karamansky shore towards the north from the Makhachkala post there are the signs of the ash washout of the sand material towards the land (the oblasts with the development of the hilly sands are quite spread over the place).

4. North-Sulak system, 10 km long, lays from Sulak mouth to the northern part of the Sulak bay.

6. Agrakhan system, including the coasts of the Agrakhan peninsula, the length is 84 km.

7. The creation of the artificial cut in the body of the Agrakhan spit for the flow of tersky waters led to the formation of the “new delta” of Terek, that divided this system into two subsystems: a) the southern and b) the northern. However, the unity of the system gets restored during the strong wave effect or small flow through the Main bank.

There are positive conditions for quite significant ash washout of beach sands towards the land. The repeated pasture of the cattle and the destroying of the flora coverage on separate sections of the Agrakhan peninsula favour it. Thus, the calculations note the existence of the convergence of washout flow a bit to the south from the channel oblast, separating Chechen island from the Agrakhan peninsula. Indirectly the convergence is confirmed by the maximal width of Agrakhan peninsula in this place as well as by the maximum local growth of the marine part for the past years.

Picture 2.9.3.1. The scheme of the litho-dynamic division to the regions of the Caspian coastal within the limits of the Russian Federation [16]: Main litho-dynamic oblasts (I-III) and the systems forming them (1-10): I – Derbent-Agrakhan; II – Terskaya (Agrakhan gulf); III – volgo-kizlyar; 1 – Derbent oblast; 2 – Manasskaya oblast; 3 – Caspiysko-makhachkalinskaya oblast; 4 - Severo-Sulak oblast; 5 – Agrakhan oblast; 6 – Terskaya; 7 – Suyutkinskaya oblast; 8 – bryanskaya; 9 – Kizlyar oblast; 10 – Voljskaya oblast.

Map symbols: 1 – coastal line; 2 – borders of the litho-dymanic oblast; 3 – borders of the litho-dynamic systems.

Table 2.9.3.1. Main characteristics of the litho-dynamic systems of the Caspian coasts [16]

6. Terek system (Agrakhan gulf), the length is 76 km from the north-eastern ledge of Checehn island to Kraynovka settlement. The development of these coasts is defined by the convergence of pileup flows, directed inside the Agrakhan gulf as well the by the inflow of the alluvial pileups from the terek channel.

7. The system of Suyutkin spit with the length of 36 km is defined from the point of divergence of pileup flows at Kraynovka settlement up till the spit distal. The major washout is observed at the root part of the coast while the accumulation takes place not far away from the distal part. The turn of the direction of the distal of the spit for 90-110° testifies the of the full stoppage of the alongshore transport of pileups and that allows to look at this geomorphologic object as at an litho-dynamic system. In the back part of the spit under the angle of 45° towards the coast line there is a unity of ash pileups – the ridge sands that testify about the washout of sand towards the land.

8. The system of Bryanskaya spit, long as 26 km, is characterized by the obvious similarity of the litho-dynamic processes happening here and their space placement in comparison with the system of Suyutkinskaya spit. Let us pay attention to the significant ash washout towards the coast in the form of ridge sands, breaking the coastal line under the angle of 40-60° . One can consider that Suyutkinskaya and Bryanskaya spits are the most significant ones as per their forms, created under the influence of wind waves.

9. The Kizlyar litho-dynamic system of 110 m of length combines both Kyzlyar coasts and the coasts till the Ivan-Karaul peninsula and the traverse of Caspiysk settlement, adjoining the Volga delta. The coasts of this region are characterized by the sharp weakening of the effect of wind waves. The wave effect is realized mainly during the significant wind pileups. The coasts are characterized by the exclusive shallowness, the bents of the coastal slope to the depth of 5 meters are altogether 0,000125. The distribution of the water leads to the wide development of the phytocenosis on the shallow waters. The phytogenic coasts demonstrate the most colorful processes. The wealth of the production leads to the blossom of the Zoo Bentoce and the forms of the relief created here look mostly here like the sand-bars, formed by the rejection of the shell material from the bottom. The reed flora promotes the sediments within the frames of the litho-dynamic system of suspension, arriving here under the effect of directions, coming from the Volga delta.

10. the Volga litho-dynamic system is a shallow in-mouth of the coast of the Volga river, having the length of 150 km along the shore. The analysis of the distribution of the depths of the in-mouth seaside, done on the basis of navigational maps of the scale 1:200 000 to the depth of 5 meters, allows to conclude that the shallow areas deep as 1 meter prevail in number. There are about 27 % of the surfaces like that. At the same time the meter distribution of the depths in the range from 1 to 5 meters find close parameters of frequencies from 14 to 17 % in each of the meter ranges. The islands of delta and the dewatering cover the space of 5 and 7 % squares accordingly. The influence of the roughness during the given distribution of the depths and bents appears to be the essential one only at the marine boundary of the delta. The constant current, acting along the perimeter of the delta of Volga to the east brings a huge volume of suspension towards the Kizlyar gulf. Before the weight material reaches the Kizlyar gulf it bumps into the Volgo-Caspian channel, cutting through the submarine part of delta from north to south till the depth of 5 meters. According to the data, belonging to the 50-s of our century from 5,5 to 7 millions of cubic meters of soil gets piled up in the channel annually. It is possible that the last parameter is a raised too high, however, one should note that the significant volumes of the pileups along with the hard flow within the limits of the Volga delta are produced when the water flora fades away (first of all the reed growing areas).

If to enlarge the division to regions then there are three litho-dynamic oblasts within the borders of Russian costs of the Caspian Sea [16]: I – Derbent-Agrakhan one – length is about 282 km; II – Terskaya (Agrakhan gulf) – 76 km; III – Volgo-Kizlyar oblast - 322 km (picture 2.9.3.1). The presence of the first oblast is defined by the absolute prevailing on the coats of Dagestan of the alongshore movement of pileups from south to north with the convergence of pileups nearby the distal of the Agrakhan peninsula. The obstacles of the direction of such a movement are created by the ledges of capes or by the transversal coastal-marine hydroengineering constructions on the territory not exceeding 4% pf the coast length. The second oblast represents the convergence of flows of pileups into the Agrakhan gulf. The third oblast gets formed by the alongshore movement of the pileups frm one side and the in-flow of pileups from the delta of Volga, from the other side, towards the sedimentation center of the Kizlyar gulf.

SECTION 1

SECTION 2

SECTION 3

SECTION 4

SECTION 5

SECTION 6

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