ifir m TL 400

Draft Translation 400

RECOMMENDED PRACTICE FOR COMBATTING ICE JAMS <0 % a V.l. Sinotin et al.

August 1973^

CORPS OF ENGINEERS, U.S. ARMY COLD REGIONS RESEARCH AND ENGINEERING LABORATORY HANOVER, NEW HAMPSHIRE l APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. ' SC" Draf t^Translation 400 ' HP ?C 7 * Jj

f % ENGLISH TITLE: RECOMMENDED PRACTICE FOR COMBATTING ICE JAMS

FOREIGN TITLE: ( METODICHESKIE UKAZANIIA PO BOR'BE S ZATORAMI I ZAZHORAMI L'DA*V

~ ' 3 ,

AUTHOR: ’ V. I. Sinotin "et al.

SOURCE: Metodicheskiye Ukazaniya po Bor'be s Zatorami i Zazhorami L'da.yMinisterstvo Energetiki i Elektrifikatsii SSSR^/Glavtekhstroyproyekt (USSR Ministry of Power Engineering and Electri­ fication, Main Technical Construction Project), All-Union Scientific Research Hydraulic Engineering Institute imeni B.Ye. Vedeneyev, Power Engineering Press, Leningrad Branch, 1970, p 1-151

Translated by U.S. Joint Publications Research Service for U.S.‘'Army Cold Regions Research and Engineering Laboratory, 1973, 106 p.

NOTICE

The contents of this publication have been translated as presented in the original text. No attempt has been made to verify the accuracy of any statement contained herein. This translation is published with a minimum of copy editing and graphics preparation in order to expedite the dissemination of information. Requests for additional copies of this document should be addressed to the Defense Documentation Center, Cameron Station, Alexandria, Virginia 22314. LIBRARY

JUL 1 3 2010

Bureau ot Reclamation I«

UDC 551.326.83

RECOMMENDED PRACTICE FOR COMBATTING ICE JAMS

Metodicheskiye Ukazaniya po Bor1be s Candidate of Technical Sciences Zatorami i Zazhorami L'da (English title V. I. Sinotin et al. as above). Ministerstvo Energetiki i Elektrifikatsii SSSR, Glavtekhstroy- proyekt (USSR Ministry of Power Engineer­ ing and Electrification, Main Technical Construction Project), All-Union Scien­ tific Research Hydraulic Engineering Institute imeni B.Ye. Vedeneyev, Power Engineering Press, Leningrad Branch, 1970, p 1-151

CONTENTS

Page

Foreword 3

Terminology 6

Chapter 1. GENERAL INFORMATION

1. Ice Jam Definition 7 2. Ice Jam Formation 8 3. Location of Ice Jams 10 4. Factors Influencing Ice Jam Formation 12 5. Ice Jam Classification 14 6. Methods of Combatting Ice Jams 15 7. Single Preventive Measures to Combat Ice Jams 16 8. Repeated Preventive Measures to Combat Ice Jams 18 9. Principles Governing Preventive Measures for Combatting 20 Ice Jams 21 10. Destroying Ice Jams 11. Remarks on the Organization of Jam Countermeasures 23

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Page

Chapter 2. FIELD OBSERVATIONS OF ICE JAMS AND DATA ANALYSIS 25

1. Ice Jam Observations 25 2. Data Processing of Ice Jams 29 3. Ice Jam Forecasting 30 4. Predicting the Strength of Ice Jams 32

Chapter 3. ARTIFICIAL WEAKENING OF ICE 34

1. Using Radiant Heat to Destroy the Ice Cover (Dusting Snow-Ice Covers) 34 2 . Chemical Destruction of Ice Cover 41 3. Inhibiting Ice Accretion in Winter 44

Chapter 4. MECHANICAL DESTRUCTION OF ICE 46

1. Ice Cutting Machines and Their Characteristics 46 2. Using Icebreakers to Prevent and Combat Ice Jams 52

Chapter 5. ARTIFICIAL ICE JAMS AND STRAIGHTENING OF CHANNELS 58

1. Artificial Ice Jams 58 2. Channel Straightening to Prevent Ice Jams 61

Chapter 6. USING AIRPLANES TO PREVENT AND DESTROY ICE JAMS 65

1. Aerial Ice Surveys 65 2. Using Planes for Explosive Work 66 3. Aerial Bombing 67

Chapter 7. PREVENTION AND DESTRUCTION OF ICE JAMS WITH EXPLOSIVES 70

1. General Information 70 2. Ice Jam Prevention with Explosives 71 3. Explosion of Large Ice Fields and Jams 75 4. Explosive Destruction of Ice Jams 80 5. Using Helicopters for Explosive Work 80

Chapter 8. PASSAGE OF ICE THROUGH HYDRAULIC STRUCTURES DURING CONSTRUC­ TION AND USE OF HYDROELECTRIC STATIONS WITHOUT ICE JAM FOR­ MATION 83

1* General Conditions for Passage of Ice Through Structures 83 2• Plan for Ice Passage During the Erection of Hydraulic Structures on Rivers with a Heavy Ice Flow 86

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Page

87 3. Passage O f Ice 88 4. Passage Of Ice 90 5. Passage of Ice 91 6. Slowing o f Ice

Chapter• 9. HYDRAULIC AND 93 TO PREVENT AND COMBAT ICE JAMS

1. Ice Jam Formation 93 2. Preventing and Combatting Ice Jams 95 3. Hydraulic Regulation of the Current to Inhibit Ice Jam Formation 97 4. Thermal Regulation of Water Bodies and Currents to Inhibit Ice Jam Formation 98

BIBLIOGRAPHY 103

FOREWORD

Ice jams are inseparable occurrences in the annual cycle of the life of many rivers. Ice jams are typical of most USSR rivers. They represent a serious danger for two reasons : in relation to the floods which they cause and the possibility of destruction of various hydraulic engineering struc­ tures by ice.

The floods caused by ice jams compel us to transfer to safe locations the large industrial objects and increase the cost of building hydraulic engineering and other structures. Every year, the ice jams inflict tremen­ dous losses on the national economy while in individual unfortunate years, these losses increase by many times.

For the development of efficient measures for combatting the ice jams, it is necessary to have a thorough knowledge of the physics of the phenomenon and the causes engendering it. The attention of many organizations is being directed toward a study of the ice jam occurrences on the USSR rivers. We have studied the processes of ice jam formation on a number of large rivers (Yenisey, Volga, Ob', Dnestr, Northern Dvina, and Lena), we have conducted studies of the ice jam processes on the Angara River and on the rivers in the Caucasus and Central Asia, we are performing studies with the purpose of developing methods for predicting the ice jams on rivers; we have completed a number of studies on the application of various methods of influencing the ice runoff.

As a whole, however, the processes of ice jams have not yet been adequately studied. Specifically we have not developed bases for the theory

- 3- «r

of formation, stability and breakdown of ice jams; we have studied inadequately the physico-mechanical properties of ice under various conditions; a generally, recognized classification of ice jam occurrences and a listing of the jamming sectors is lacking and we have not established to a complete extent the ef- fectivity of any given means of combatting the ice jams under the various con­ ditions of their formation. Such a situation is explained in terms of the complexity of modeling these phenomena under laboratory conditions, with the awkwardness and high cost of full-scale studies, with the poor state of study of the individual general problems in ice engineering and by the inadequate attention paid to this question.

We still lack instructive documents of a procedural and standardizing nature on combatting and avoiding ice jams. This leads to the situation that the preventive measures for combatting these occurrences based on regulating the mechanism of river breakup, runoff of ice and its physico-mechanical properties are rarely utilized.

Also we frequently have cases when for the breakup of ice jams, we em­ ploy methods not yielding the necessary results and sometimes leading to un­ desirable consequences and to a useless expenditure of government funds.

For example at the present time the methods of combatting ice jams reduce mainly to a timely mechanical destruction of the ice cover in the locations threatened by jams and the elimination of developed jams by ex­ plosions and bombing; this is becoming quite popular owing to the possibility of operational intervention. The explosions and bombing also yield a negative effect associated with killing fish and the risk of inflicting damange to populated points, and as a whole is undesirable. At the same time, the effec­ tiveness of these methods is by no means always the same and depends on the features involved in the ice jam.

The modern achievements of science and technology and available ex­ perience permit us to consider the ice jam formation as physical processes subject to control. The loss caused by them even now can be reduced to a definite minimum under the stipulation of a proper organization of combatting these phenomena.

For the purpose of facilitating this problem, we have compiled the present "Recommended Practice for Combatting Ice Jams". In the compilation of these guidelines, we have utilized the experience accumulated in the USSR for the control of ice occurrences and combatting the ice jams which have already formed. Since the jamming of ice is regarded as the most dangerous phenomenon, the greater part of the suggested "Recommended Practice has been devoted to ice jams.

As we have already indicated, many facets of the complex problem of counteracting ice jams have still been inadequately studied and the available experience and objective data are insufficient for a thorough substantiation of the recommendations.

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Moreover owing to the complex nature and the diverse conditions involved in the origin of the actual ice jams and blockings, the effort toward develop­ ing standard measures for combatting the jams and blockings would in principle be invalid.

Guided by this, we adopted the following principle for compiling the "Standard Practices". In the first chapter we present information of a general nature, the classification of the occurrences and certain concepts concerning the choice of a system of measures for counteracting the ice jams. In the subsequent chapters, we clarify in more detail the individual procedures and methods of preventing and counteracting ice jams, and the features involved in their application under different conditions. In the "Standard Practices , we do not cite detailed descriptions of actual cases. They can be found in the literature listed at the end of the document.

In this manner the purpose of the present "Standard Practices is to aid in selecting the most feasible combination of measures for the actual local conditions. The "Standard Practices" should therefore not be regarded as a standardizing document.

Subsequently, as a result of extending our knowledge concerning the nature of ice jams and the accumulation of experience in controlling them, it will be possible to proceed to a development of standard systems, for actual rivers, of counteracting the formation of ice jams. Therefore the data in "Standard Practices" has a tentative nature.

The present "Standard Practices" are meant for specialists in various disciplines: hydraulic technicians and hydrologists, aviators and demolition experts, water transport workers and water management personnel, etc., par­ ticipating in some way in the prevention and combatting of ice jams on rivers and reservoirs. The recommendations given in the Standard Practices are also useful for the workers in the Soviet and party apparatus organizing the struggle against ice jams and blockings.

The development of the present "Recommended Practices" was conducted by the All-Union Scientific-Research Institute of Hydraulic Engineering imeni B. Ye. Vedeneyev of the USSR Minergo with the participation of The State Hydrologic Institute and of the Arctic and Antarctic Scientific-Research Insti­ tute of the Main Directorate of the Hydrometeorological Service under the Soviet of Ministers of the USSR, of the Leningrad Institute of Water Transport under the RSFSR Ministry of River Fleet, USSR Academy of Sciences Institute of Geography, the "Soyuzvzryvprom" Trust under the Ministry of Installation and Special Construction Work of the USSR. In the development, those who took part included Candidate of Technical Sciences V.I. Sinotin (AUSRI HE)(direc­ tor of the study), Professor B.V. Proskuryakov (LHMI), Prof. I.S. Peschanskiy and Candidate of Technical Sciences Z.I. Shvayshteyn (AASRI), Candidate of Technical Sciences V.V, Balanin and R.I. Shcherbakova (LIWT), Candidate of

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Technical Sciences R.A. Nezhikhovskiy (SHI), Candidate of Geographic Sciences Ye. N. Tsykin (Geographic Institute of USSR Academy of Sciences), Engineer I.L. Bleyman (Trust for Drilling and Blasting Operations of the Glavspetsprom- stroy), Candidate of Technical Sciences A.I. Pekhovich, I.N. Sokolov and V.M. Zhidkikh, Engineers V.N. Kamovich, L.A. Shmeleva (AUSRI HE), Candidate of Technical Sciences G.A. Morozov and V.A. Koren'kov (Sub-branch of AUSRI HE).

TERMINOLOGY

A gaging station is a station provided with special equipment for the systematic measurement of the water level. We differentiate the pile-supported, rod-type, pile-rod type and other forms of water gaging stations.

The water level is the height of water surface above a provisional hori­ zontal plane (actual zero point) expressed in cm. If this plane is the sea surface, the level is normally expressed in meters and is referred to as the absolute reference mark (control point).

The longitudinal profile of a river is a graph on which we reflect the longitudinal vertical section of a river, with plotting of the elevation of the water surface and the bottom line (along the channel line or channel).

The longitudinal profile of the water surface of a river is a graph in which we indicate the elevation of water surface along the river's length.

The longitudinal gradient of the water surface (stream gradient, for short) is the ratio in the difference in heights of the water surface in a sector to the sector's length.

The water flow rate is the quantity of water passing through a river cross section per second; it is normally expressed in cu m/sec.

The freezing of a river is the process of formation of a stationary ice cover on a river.

Freezeup is the establishment and also the existence on the reservoirs and waterways of a stationary ice cover.

Ice push is a slight shifting of the snow cover in a separate river sector.

River breakup is the process of the disintegration of the ice cover on a river.

- 6- The ice debacle is the motion of compact (crystalline) ice along a river. We differentiate between spring and autumn ice debacle.

Frazil (slush ice) includes various formations of loose ice in the form of lumps, garlands etc. It can be in motion (slush passage) or can exist in the form of accumulations beneath the ice cover.

Intra-water ice consists of ice crystals (needles, grains, plates) developing during the supercooling of water.

Bottom ice is a form of intra-water ice? it forms at the bottom of rivers.

Zakrainy are belts of open water along shore; they appear before the breakup of a river.

Shore ice (zaberegi) consists of belts of stationary ice along the shores; they originate during the ice formation on a river.

Permanent open water pool (polyn'ya, mayna) is a section of open water surface amid an ice cover.

Ice edge is the boundary of stationary ice cover and the open water surface.

An ice jam or ice blocking is an accumulation of ice in a channel, re­ stricting the cross section of the river and causing a rise in water level at the point of buildup and in a certain sector above it. The ice jams usually become formed in spring on breakup of a river; the accumulation of ice in a jam consists chiefly of the large and small broken floes. The ice blockings become formed during the ice formation on a river and during the winter season. The accumulation of ice during a blocking consists chiefly of slush and in part of small broken floes.

The definitions listed above for rivers pertain equally to the reser­ voirs, canals and other water features.

CHAPTER 1

GENERAL INFORMATION

Section 1. Ice Jam Definition.

An ice jam represents an accumulation of ice in a channel, restricting the cross section and by the same token causing a rise in water level at the point of accumulation and over a certain sector above it. At this time the LIBRARY

-7- JUL 1 3 2010 Bureau of Reciarn.-i • . Dftnvpr Jf

ice accumulation consists chiefly of large and small broken floes. Usually the ice jams become formed on breakup of a river and are caused by the lack of simultaneity in the breakup and the inadequate ice-transporting capacity of a river.

The ice blocking is the accumulation of slush in a river channel ac­ companied by the plugging of a certain part of the cross section and by a rise in water level.

The largest ice gorges are formed during the spring ice debacle; the ice jams usually take place in the pre-ice formation period and also winter in the presence of large nonfreezing river sectors.

In a number of cases, the processes of ice gorge and ice jam formation have an influence on each other. Thus an ice cover of appreciable thickness having formed as a result of the freezing-together of the jammed sludge mass­ es in the free-ice formation period, during the spring iceout can serve as a cause for holding back the ice and can became the focus of the springtime ice clogging. Usually in the places where in autumn ice jams have occurred, the level at establishment of freeze-up is usually high; therefore a delay in the river's opening occurs here and the ice cover serves as a cause for the formation of a jam. However the autumn ice gorges which usually are not characterized by much thickness can create conditions for the floating-up and freezing-together of sludge, causing the formation of autumn ice jams.

The ice jams create dangerous consequences much less often than the ice gorges. Although in many respects, the processes of ice gorge and ice jam formation are similar, the methods of combatting the jams have a specific nature associated with controlling the sludge-formation process. Therefore all the questions pertaining to ice jam formation and the combatting of ice jams have been included in a separate chapter (Chapter 9).

Section 2. Ice Jam Formation.

Ice jams occur in the spring period during the breakup of a river. The formation of a jam takes place when difficulties develop in the downstream movement of ice. The causes of such difficulties are diversified. In some cases, these include large volumes of ice being floated, with low flow rates of water; in other instances, these include the presence of an obstacle in the form of a permanent ice cover, etc.

The process of the formation and breakdown of an ice jam can be repre­ sented schematically in the following form. In spring with the advent of positive temperatures of air, the thawing of snow in the basin begins. The discharge of water in a river increases, the water level rises and the ice cover, floating up, is ripped away from the shores. With a rise in water level, the river width increases; between the edge of the drifting ice cover

-8 - *

and the shore, belts of open water appear, i.e. "zakrainy" (border zones). The appearance of the open zones is also favored by the eroding effect of the snow melt water, running from the slopes directly into the river.

Simultaneously under the effect of warm air and the sun's rays, the ice cover on the river becomes weakened. The time arrives when the entrain ing force of flowing water leads to the breakup of the ice cover into separate large fields which start moving. This moment is referred to as the "ice push". At this time, the displacements of the ice fields are slight and are restricted by the dimensions of the open border zones. However the ice fields have a very large mass and on collision with the shores and with each other break up fairly rapidly into large floes. The springtime ice debacle begins.

In their course, the drifting ice masses can encounter an obstacle which could be a river sector which has not yet broken up, with a continuous and fairly strong ice cover. At the edge of the ice cover, the motion of the floes is retarded and then stops completely. Under the pressure of the ice material transported by the current, the edge of the stationary ice cover becomes part­ ly broken up and appears in the form of an accumulation of ice floes slightly tilted in relation to each other. Some of the drifting floes are drawn by the current beneath the broken part of the ice edge. At this place is located the head or base of the ice clogging. The obstacle to the moving ice fields can also be various types of restriction to the channel (islands, abrupt narrows, inversions etc.).

New ice masses float up to the floes which have stopped at the broken ice edge. Under their pressure, a hummocking begins, accompanied from time to time by slight ice pushes. At this point, the surface of the river resembles a chaotic accumulation of small floes and blocks. The channel here is greatly crowded with ice. Owing to the crowding of channel by ice, the water level in the river rises. It is significant that the rise in level also occurs in a certain sector of the river above the place of confinement, i.e. in the back­ water zone. The current speed in the backwater zone decreases while the floes floating from above already have a reduced kinetic energy. The hummocking of ice gradually weakens and then stops. The process of the ice jam's formation is thereby completed.

The disruption (breakup) of an ice jam occurs either as a result of an abrupt increase in the water discharge in the river (at this time, ice floats up in the jam) , or as a result of the influence of warm air and melt water. Most often the breakup of an ice jam is the result of the combined effect of both factors.

The longitudinal profile of a river during an ice jam has been reflected in Fig. 1.

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Fig. 1. Longitudinal Section of Ice Jam. 1 - tail part of jam (tail of jam); 2 - leading part of jam (head of jam); 3 - lower edge (lower boundary of jam); and 4 - upper edge (upper limit of jam). Keys a. length of jam.

Section 3. Location of Ice Jams

Ice jams are typical of the medium-sized and in particular of the large plains-type and semi-mountainous rivers. On small rivers, ice jams hardly ever occur. However, ice jams are by no means typical of all medium­ sized and large rivers. For the formation of a jam, it is necessary to have a combination of specific conditions, the principal ones are: participation, in the ice passage, of large ice masses and the presence of obstacles to the ice motion.

Large ice volumes prior to breakup occur in the channels of almost all rivers in regions having a harsh climate. It is specifically for this reason that ice jams often occur in the rivers of Siberia and the Far East, whereas in the southern regions of the European sector of the USSR, they occur less often.

As we have pointed out, an obstacle to the movement of ice is usually represented by the large river sectors with a continuous and fairly strong ice cover. Therefore the intensive and frequent ice jams take place on those rivers where the opening occurs from above downstream. Such a sequence in opening is possessed by various rivers, namely:

a) on the large rivers flowing from south to north (Lena, Yenisey, Irtysh, Northern Dvina, Amu-Dar'ye etc.). In the southern (upper) regions, these rivers break up earlier than in the northern (lower), and the moving ice encounters an ice cover not prepared for opening;

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b) the rivers, the upper reaches of which are mountainous and semi- mountainous, while the lower reaches are plains type (Dnestr, Amur, Tom', Visla and others). In the upper reaches, owing to the fast current, a river will break up sooner than in the lower reaches; and

c) the rivers where after a large sector with a considerable current speed, there follows a sector with a slower speed. In the first sector, the opening occurs much sooner than in the second one.

The sequence in the opening of a river (from above downstream) is the sole factor determining the actual possibility of an ice jam. However, the location of the jam's development is caused by the morphometric features of the river and also by the hydrometeorological conditions existing in any given year.

We should differentiate the constant location of the formation of ice jams and the sectors with inconstant foci of ice jams.

IA q aware of two types of constant locations of ice jam formations.

1. Location of the break in the general longitudinal profile of the river from the sector with a steep gradient (meaning also with a fast current velocity) to a sector with a slight gradient (hence, with a slow current speed).

Under this type, we include:

a) zone of the tapering out of a reservoir's backwater (e.g. the Ob' River at the city of Kamen' on the Novosibirsk Reservoir; Neman R. at the Birshtonas settlement on the Kaunasskoye Reservoir);

b) the estuary of a river on entrance into a sea or lake (for example, Syas' R. at Syas'skiye Ryadki settlement on emptying into Lake Ladoga; Northern Dvina R. at the city of Arkhangel'sk on confluence with the Beloye More [White Sea]);

c) zone of transition from a sector of rapids to a plains sector, or from a steep to a gently-sloping sector (for example, Dalugava R. at the city of Yaunelgava below the Plyavin'skiye Rapids to the construction site of the Plyavin'skaya HES [Hydroelectrical Station) and Sukhona R. at the city of V. Ustyug);

d) the point of confluence of two rivers bearing large ice masses (e.g the confluence of the Northern Dvina and Vychegda at the city of Kotlas).

2 The place of a very sharp bend in a river (more than 110-115 ) ^ in combination with a narrowing. Typical in this respect is the sharp bend m Dnestr R. at the city of Voronkovo.

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Fig. 2. Locations of Formation of Springtime Ice Jams, a - ice jam in single-branch channel at steep bend in river; b - ice jam in multi-branch channel prior to opening of river below ice jam; c - ice jam in multi-branch channel after river breakup below ice jam; d - ice jam on expan­ sion of river; e - ice jam in tributary; f - ice jam on reservoir. The broken line indicates the sequence in formation of ice jam; g - jam of transit ice resulting from blockage of large floes transported from the above-lying sec­ tor in the narrows between islands; h - ice jam in arms of a river delta; i - ice jam prior to narrowing of river channel; 1 - ice cover not disturbed by cracks; 2 - cracks in ice without hummocks; 3 - cracks in ice with hummocks; 4 - zakrainy (open zones) ; 5 - small blocks of hummocked ice; 6 - large ice fields; 7 - rare ice passage; 8 - open water.

The inconstant locations of the ice jam formations are usually quite diversified, i.e. abrupt narrowings, sharp bends, shallows, islands, points of bifurcation, sectors with the presence of a strong ice cover over a considerable length. Often the ice jams develop in those places where in autumn during the inception of complete ice formation, ice shoves have occurred and "zazhory" (ice dams) have taken place. Cases involving the formation of ice jams at various points have been indicated in Fig. 2.

Just where does an ice jam originate in a given year? This is deter­ mined by the hydrometeorological conditions of the winter and spring seasons; above all, of the initial period of spring floodwater stage.

Section 4. Factors Influencing Ice Jam Formation

Other than the places of its formation, the most important parameter of an ice jam is its thickness, being typified by height in the rise of water level. The dependence of this value on many factors causes a consider­ able element of randomness during its determination, in many cases eliminating

- 12- the possibility of predicting it exactly.

Along the main factors of jam formation, we include:

a) quantity and intensity of ice arrival at the ice jam;

b) intensity of flooding, specifically the maximal (of average diurnal values) intensity in rise in water level during the iceout period; and

c) the presence of obstacles to the ice motion.

An important role is also played by other factors, namely the flow rate of water, air temperature, thickness of snow pack in the river basin, total solar radiation, sequence of rivers' opening in the basin, and other aspects.

It is most simple to disclose the role of individual factors when the ice jam forms at a constant location. The thickness of ice jam and hence the rise in level are in a direct relationship to the amount of ice arriving at the ice jam. Therefore after a severe winter with little snow, with a con­ siderable volume of ice in the river channels toward the beginning of spring, the maximal jam level greatly surpasses the maximal level following a mild winter with heavy snow, with relatively small ice volumes. The quantity and intensity of ice transported by the current is related, inter alia, with the intensity of the river's opening. At a simultaneous opening of all the main rivers in a basin, the ice runoff is high; as a result, a tremendous ice jam becomes formed. In case of an uncoordinated opening of rivers, the ice run­ off and the intensity of ice debacle are slight; accordingly, the ice jam is also minor.

The influence of water flow rate during the opening of a river, at con­ stant location of ice jam formation, is manifested in the fact that the higher the flow rate, the more intensive the spring ice drift and the higher the maxi­ mal ice jam level. At the same time, in case of a high flow rate of water, the ice jam head is shifted downstream; therefore in the tail of the ice jam and in the zone of the backwater's tapering out, the effect of water flow rate may not be discerned.

The high air temperature after the formation of an ice jam favors its rapid disintegration, chiefly owing to the influence of warm melt water. How­ ever an intensive warming prior to opening promotes the formation of an ice jam. In this context, in connection with the abrupt increase in the output of water, the ice cover not prepared for opening is broken up mechanically.

The process of opening an ice jam formation in a river sector with in­ constant location of ice jam formation transpires much more complexly. Above all, let us point out that in spring the ice shoves and ice drift begin only after the water level in a river exceeds that level at which in autumn the inception of the complete ice formation had taken place. Moreover, owing to

- 13- the fluctuations in air temperature and in water discharge during the autumn season (see the description of ice dam formation process, Chapter IX), the establishment of complete ice formation occurs at different sectors of a river at irregular excess of the level above the low-water stage. In the places where in autumn we recorded the ice pushes and ice dams, the level on estab­ lishment of freeze-up is high; therefore a delay in opening occurs here. A further reason for the delay is that in the locations indicated, the ice cover is thicker and stronger than on an average for the river. In this manner, the locations of autumn ice pushes and ice dams are often the points involved in the formation of springtime ice jams.

The opening of a river is usually accompanied by an increase in water flow rate. In this connection in the river sector under review, chains of ice jams develop with slight time lags. The breaking of one jam leads to the opening of a certain river sector and is completed by the formation of another jam downstream, etc. The length of existence of such ice jams is reckoned in hours (the very longest, 12-18 hours).

The process develops differently when the water discharge is relatively slight and more or less constant. At this time, the ice masses floating up to the ice jam have a low kinetic force; the entraining force of current beneath the ice jam is also slight. Breakage of the ice jam does not occur, there takes place only a hummocking of the ice at the upper limit of the jam and the ice jam itself is propogated upriver. The length of jam reaches 10-15 km and on the Siberian Rivers, sometimes up to 35 km. Such ice jams large in extent have great stability. The length of their existence on the rivers in idle European sector of the USSR sometimes reaches 3-5 days while in the North of Siberia, they sometimes endure for 8-10 days. The artificial destruction of such ice jams is practically impossible.

Section 5. Ice Jam Classification

At the present time, we have not yet developed a generally adopted classification of ice jams. The classification can be conducted according to various criteria. Thus we can consider the classification presented be­ low, based on a consideration of hydrologic conditions and the points of ice jam formation, which is appropriate to the problems involved in counteracting this phenomenon.

Ice jams on rivers can be divided into two types.

1. River channel jams.

a) directly at the edge of ice formation at irregular opening of the river, usually flowing from south to north;

b) at points of a decrease in the ice-passing capacity of a river (any kind of restriction, points of abrupt decrease in slope and current velocity);

- 14- 2. Pressure jams

a) in the zones of the tapering-out of a reservoir's backwater;

b) in the deltas and river estuaries flowing into seas and lakes or into the rivers which breakup later on.

The region of the formation of type 2 jams and also in certain cases the lb types (for example, transition from a sector of rapids to a plains sector, or a sharp bend with a narrowing) is usually limited, i.e. it is known beforehand. In connection with this, for the jams of this type, the feasi­ bility of preventive measures of counteracting these jams is quite obvious.

The channel—type ice jams, especially of type a) can develop in the most diversified locations along the river, depending on the preceding hydro­ meteorological conditions. This circumstance often greatly complicates the conduct of preventive measures against an ice jam.

Section 6. Methods of Combatting Ice Jams

The combatting of ice jams can be solved in three ways:

1) by adopting preventive measures on controlling the process of ice formation and its runoff, i.e. on the elimination or weakening of the causes and conditions of the origination of ice jams;

2) by means of direct combatting of the ice jams which have already formed; and

3) by means of a timely forecast of the location of an ice jam forma­ tion and its thickness.

These methods of combatting ice jams can be utilized either individually or in any combination, depending on the circumstances. The timely forecast of the location and maximal rise in level from the ice jam or ice dam already permits a considerable decrease in the damages from these occurrences by way of adopting the appropriate measures of preparing to counteract them.

At the present level of the development of hydrology, certain possi­ bilities of predicting the maximal ice jam level are available only in those instances when the location of the jam is constant from year to year and the main factors are the degree of severity of winter and the nature of the es­ tablishment of complete ice formation. More details of the forecasts of ice jams have been given in Chapter II.

The most effective, reliable and desirable technique is the conduct of preventive measures. However this approach is ordinarily applicable in those

- 15- cases when we are aware of the location or typical region of ice jam formation. The measures of a precautionary nature can be divided into one-time and re­ current ones.

The elimination of ice jams which have formed is usually applied in the case of the formation of an unexpected ice jam in an undesirable location or when owing to the combination of unfavorable circumstances, a serious ice jam is forming notwithstanding the performance of the preventive measures.

Section 7. Single Preventive Measures to Combat Ice Jams

The most effective of the preventive measures capable of eliminating completely the ice jams in a river are the construction of a series of hydro­ engineering complexes and the establishment of the necessary conditions of their operation. In this connection we can achieve a basic change in the hydro- logic, thermal and ice regime pertaining to the water flow.

The erection of individual hydroengineering complexes can eliminate the ice jam development in the ranges occurring in the backwater zone but such a step will create conditions for the origination of new ice jams in the tapering-out zone of the backwater and below the range of the hydroengineering facility. Although as a rule the guiding motive in building a hydroengineering complex is not to combat ice jams, it is necessary to consider this circum­ stance in the planning of a hydroengineering facility and a comparison of the alternatives.

Certain outlooks involved in the control over the process of ice jam formation in the headwater (upper reach) of an individual hydroengineering com­ plex provide the possibility of maintaining the elevation marks of a reservoir at the necessary level. For avoiding the formation of ice jams in the region of the backwater's tapering-out in small reservoirs (for example on the upper Danube), with the aid of icebreakers, tasks are performed on creating along ■the reservoir an ice—free channel with a width of around 100 m. The broken ice is removed into the lower pool of the hydroengineering complex while in the open water channel which has formed, the ice arriving from the upper river sec­ tor is received. The most effective technique of transporting the ice along the channel mentioned during its clearing and the subsequent passage of ice arriving from the upper reaches will constitute the proper combination of the operation of icebreakers combined with maneuvering the dam sluices. At this time, the most feasible technique of manipulating the sluices is not the main­ tenance of continuous output but the development of unsteady conditions by a rapid opening of the gates by approximately 2 m (HES Iokhenshteyn) with a sub­ sequent slow rise. Such operations are conducted 3-4 times per day. On the larger reservoirs for avoiding ice jams in the zone of the backwater's taper­ ing-out, it is evidently necessary to create beforehand a basin of open water by breaking the ice with icebreakers and removing it from the indicated basin by the methods which have been described below in reviewing the operation of

- 16- *

icebreakers. The basins which have been formed will then be able to collect the ice arriving from above, not leading to the formation of a jam.

The opposite result can be obtained if we perform an intensive treat­ ment of the reservoir prior to the high water stage. This can lead to the sinking of the ice cover to the bottom and freezing together with it, which will lead to the formation of an ice jam, as occurred in spring of 1967 on the Dubossarskoye Reservoir.

In manipulating the sluice gates, we should never forget the water down­ stream from the HES (hydroelectric station). The development of ice jams in the downstream water can be avoided if by controlling the bypass discharges according to the capacity of reservoir, we provide the necessary relationship between the increment in the flood level and the thermal preparation of the ice cover, excluding the breakup of ice prior to its necessary weakening. The lat­ ter has particular significance for the rivers flowing from south to north. Experience shows that during the presence, in the downstream part of the HES, of an ice cover, we should not permit a rise in level greater than 1 m/day, at which time the water flow rate should increase uniformly.

What has been discussed indicates the necessity of imposing specific limitations on the operation of hydroelectric stations, proceeding from the concepts of avoiding ice jam formation and the incorporation of these limita­ tions in the rules for utilizing the water resources, under development for any given hydroengineering complex and at the present time subjected to al­ most uniquely power engineering purposes.

The meliorative activities also pertain to a number of measures re­ quiring nonrecurring capital investments. At the present time, the planning of a corrective route is conducted proceeding from the condition of the water throughput capacity and transport of sediments, wherein one ignores completely the condition of providing the necessary ice-passing capability. On the rivers which are prone to have ice jams, this can never be tolerated.

In a general case, in addition to the requirement of observing the con­ dition under which the ice discharge is less than or equal to the ice-passing capacity of a channel in any range of the rectifying course, it is necessary to strive toward the formation, if possible, of a uniformly bending or recti­ linear single-arm channel in which there are reduced to a minimum the addi­ tional obstacles for the transport of ice. In this connection, at the bends in a channel, taking into account that for the transport of ice, usually not all the surface of the river is utilized, it is desirable to make a certain widening of the course, the extent of which can be established in a first ap­ proximation theoretically with a consideration of the kinematics of the sur­ face flows of current and then corrected on the basis of natural observations.

An illustration of the basic approach discussed here to the planning of a corrective course, excluding the occurrence of ice jam formation, is the

- 17- 4

straightening of the Danube River in the vicinity of Bratislava. As a result of straightening the channel and the truncation of many tributaries, we suc­ ceeded in obtaining the following results. Prior to the conduct of the regu­ latory operations, the maximal levels in the annual section occurred in February and comprised 25.8% of the cases while 48.7% of the cases occurred during the four winter months. After control, these figures comprised 8.6 and 22.9% respectively, i.e. the large share of the maximal levels was shifted to the June-July months when the maximal discharges are passing in the river.

In an actual solution to the problem of the application, in any given sector, of rectifying operations, it is necessary to consider that this tech­ nique of avoiding ice jams requires appreciable capital investments. Taking into account that on many rivers, the sectors prone to have ice jams occur in the regions which in the future should be covered by the backwater of the hydroengineering complex earmarked for construction, the conduct of regulatory measures can be justified only if it would pay for itself during the period prior to the construction of the hydroengineering facility. The questions involved in the passage of ice in the sectors prone to have ice jams should also be considered in the conduct of other forms of transport line operations (during the construction of bridge crossings,- layout of channels, selecting the locations for dumping dirt etc.).

Section 8. Repeated Preventive Measures to Combat ice Jams

The basis of all the repeated preventive measures which are conducted almost every year is the control of ice runoff by means of influencing the process of a river’s opening, specifically: the weakening and destruction of ice cover in order to accelerate the opening in one sector, intensification of the ice cover and delay of opening in another sector.

The weakening and dismemberment of the ice cover should as a rule be conducted directly in the region of the ice jam's formation and at a relatively slight distance below it in order to facilitate the passage of ice arriving from the upper reaches. The length of the sector in which the ice weakening is performed should be determined in each actual case depending on severity of winter, nature of ice formation, weather forecasts and the pattern of flood­ ing during the ice-out period.

For accelerating the opening, it is most effective to utilize powerful icebreakers while in the case of slight depths, it is best to utilize ice-cut­ ting machines. The accelerations of the river's opening can be obtained by application of explosives. The ice-cutting routes and the arrangement of charges at this time needs to be planned, considering the currents in the sec­ tor, the location of islands, bends in the channel, shoals etc. in such a way that at the time of ice shove, the ice cover would prove to be divided into longitudinal strips.

- 18- As a further means for weakening the ice cover and facilitating the operation of icebreakers, we can utilize the darkening of ice by dark powders or sprinkling with chemicals. A significant effect from darkening is achieved only during clear weather and the absence of snowfall during the free-flood period.

The weakening of the ice cover can also be achieved with the aid of measures promoting a less intensive accretion of ice during the winter. For this purpose, we should conduct an artificial control over the thickness of snow cover on the ice. Specifically, we can recommend the application of penol'd(?) as an economical heat-insulating material. However, one should ap­ proach this technique cautiously, not overloading the ice cover and avoiding the possibility of the formation of "snow" ice.

As a preventive measure for delaying the opening, we can recommend the artificial intensification of the ice cover upstream from the hypothetical location of the ice jam formation. Such a measure partly or completely stops the runoff of ice into the sector located downstream, creating a jam in a safe location.

For intensifying the ice, we can utilize: removal of snow from the sur­ face of ice cover, frosting operations and the freezing of ice. The first method can be mechanized with the aid of bulldozers and snowplows. The actual mechanization of the freezing process does not encounter any difficulties. The intensification of the ice cover in certain cases can be accompanied by anchoring it to the shores by the freezing-in of cables, logs, and so forth. In this manner, for controlling the ice regime for the purpose of avoiding ice jams, we can utilize the following techniques:

- the weakening of ice by sprinkling it with dark powders or chemical materials ;

- the breaking of ice with icebreakers;

- the breaking of ice by icecutting machines;

- the disruption of ice by explosions;

- the artificial intensification of ice cover for the purpose of creating ice jams upstream from the sector which is being protected;

- the application of a varying type of heat insulation for restricting the accretion of ice cover;

- the weakening of ice by influencing it with modifying agents (Modify­ ing agents are substances which, upon being added to water, alter its physical properties)• This technique of weakening the ice is in the stage of experimen tal study.

- 19 - A

Section 9. Principles Governing Preventive Measures for Com­ batting Ice Jams

For a successful elimination of the loss inflicted by ice jams, it is necessary to become oriented toward the application of measures preventing their formation. The counteracting of a jam which has already formed is in­ comparably more complex and less effective than the measures for its preven­ tion. It is necessary to point out that in many instances, an ice jam prior to the time of its successful elimination can manage to inflict losses the total of which exceeds greatly (occasionally by several times) the expendi­ tures for the conduct of preventive measures. The preventive measures of com­ batting ice jams are especially effective in those cases when the location (or the approximate region) of an ice jam’s formation is known in advance.

The main problem in planning to combat the ice jams is the establish­ ment of the best combination of preventive measures with allowance for the local conditions and climatic features in effect during a given year.

The conduct of operations on accelerating the opening of a river and the passage of ice in individual ranges or junctures where the most frequent and most serious ice jams occur can promote their weakening at a given loca­ tion but in a number of cases it is capable of leading to the creation of more severe ice passage conditions and to ice jam formation at the sectors farther downstream. Therefore the planning of measures for avoiding jams should be accomplished proceeding from a review of the conditions involved in the jam- free passage of ice over a river's entire length or in significant sectors of it, in any event taking into account the possible effect of measures in­ tended for a given point, on the ice passage conditions downstream.

In this context, it is necessary to consider that for the rivers flow­ ing from north to south (or in a direction close to that indicated), the phenomenon of ice jam formation is occasioned by the difference between the conditions of the water and ice transporting capacity of the channel and by the nature of the variation in water discharge and ice output along the length of a river.

In the simplest case of a rectilinear single-branch channel, the water­ transferring capacity is the product of the useful cross section of flow uav times the area oo of this section, i.e. uav cj, while the ice-passing capacity is described by the expression V SUrf.av.B hA k ' where B = width channel; t^surf av = avara9® surface flow velocity over channel width; h^ = ice thick­ ness; k = coefficient depending on form of channel; for rectilinear form, k = 0.9; for other forms, k = 0.8. In this manner, in the indicated simplest case, the jam-free passage of a certain constant ice discharge is theoretically possible, under the stipulation that kzr surf.af. B = const over the entire length of the channel sector under consideration.

- 20 - In nature the formation of a river channel is achieved by water flow under the condition that = cons^ and in a number of instances (owing to a change in depths), the condition of the constancy of ice passing capacity is not maintained. In addition, in reality in place of a rectilinear single branch channel, as a rule we have a curvilinear and often multi-branch channel where a number of additional "difficulties" appear for the advance of the ice. In this manner the appearance of jams in most of our rivers flowing south should have become inevitable. However this does not occur, because discharge rate Q downstream increases while the ice discharge Q/\ declines owing to the thawing of ice. On the indicated rivers or individual sectors of them which are existing in a free state, the jam-free passage of the ice is possible provided that curve = f (? ) (where Z = length of river from source to mouth) never intersects curve k IX ^ „ B h* t remaining continuously be- low it. At disruption of this condition, an ice jam should become formed.

A different pattern occurs on the rivers flowing from wouth to north. Here the amount of ice moving downstream of the river not only does not de­ crease but in most instances, it increases. In addition, the flood wave and ice arriving from the upper reaches encounter enroute the undisturbed ice cover; this inevitably leads to the formation Of ice jams.

It follows from this that in the first case (river flowing from north to south), in considering the measures from preventing jams, we can refer to the problem of the jam-free passage of ice along a river; however, in the second case (river flowing from south to north), as a rule the question should be raised as to the measures reducing or eliminating the jam at the given point where it causes significant damage and concerning transferring it to another point where the formation of a jam will not inflict a loss on the national economy but rather in certain cases is even desirable (as an example, we can indicate the Northern Dvina River, where an ice jam at Arkhangelsk always causes considerable damage, while an ice jam in the vicinity of Vozhderomka is extremely important for agriculture, since it provides the flooding and necessary irrigation of the floodplain meadows. In addition, an ice jam near Vozhderomka always lessens the ice jam near Arkhangel'sk, and hence against this background is a desirable measure).

The development of the best combination of preventive measures for the given conditions should be conducted by way of the same planning process which is utilized for the hydraulic engineering structures. In this connec­ tion, it is not excluded that in certain cases, the realization of nonrecur­ ring protective measures (damming, transfer of objects) can prove more feasi­ ble economically.

Section 10. Destroying Ice Jams

Whenever it is impossible to predict the location of a channel ice jam's formation, particular attention must be paid to the measures for protec­ tion against floodings and the most advantageous method for destroying an ice

- 21- jam in order to avoid or to reduce flooding. In final analysis, the problems consists of accelerating the breakup of the jam since it is only in this case that the reduction in the level can occur.

The destruction of jams which have already formed can be conducted with the aid of icebreakers, explosions, dropping bombs from aircraft, using artil­ lery firing, thermite mixtures, and regulating the level of a reservoir.

The clogging of ice in natural state is basically disrupted under the effect of the hydrostatic pressure of water accumulating above the jam; other factors include the heat conditions and the attracting streamflow passing through the jam. The essence of combatting the ice jams should therefore con­ sist in intensifying the attracting streamflow running through the jam. This promotes the transport of individual floes from the jam and decreases the resistance of the jam's body to the flow which in turn increases the carrying capacity and reduces the backwater level of the water.

The development of this process can be achieved by creating, in the lower part of the ice jam's front, openings in the form of an ice-free channel. Water filtering through the jam tends to move toward the channel which has formed and begins to wash it away, carrying the ice from the channel. On deepening the channel within an ice jam (from below upstream), the current speed in the channel increases and finally the time arrives when water pres­ sure in the jam and the attracting force of flow in the channel begin to ex­ ceed the adhesion forces of the floes with each other and with the river banks.

At this time, the breakup of the jam begins. The ice located in the central part (over the river's width) starts to move, and then all the new ice masses from the middle to the shores become involved in the motion until the entire ice mass occurring in the jam is caused to move. The ice jam's rupture occurs. The jam’s breakup is accompanied by a loss of water; therefore the movement of ice at the shores is slowed down and then even stops entirely. The ice debacle continues in the central part of the flow while at the part along shore, ice heaps remain in the form of many-tiered haphazard accumula­ tions .

Icebreakers, explosives and at times bombing are most effective for com­ batting the ice jams.

It should be pointed out that not all jams can be destroyed. For ex­ ample, the jams of considerable proportions, on the Siberian rivers, forming at relatively slight water discharges have high stability. The artificial disruption of such ice jams by the methods indicated is impossible.

Before proceeding to the destruction of a jam, it is first of all neces- sary to disclose its features and then to pinpoint the most efficient methods of destruction.

- 22- We proceed to the destruction of a jam forming during the initial ice- out period from the accumulation of local ice, after there forms (below the front of the jam) an ice-free water sector into which ice could descend from - the jam.

It is most effective to proceed to the destruction of a jam forming during ice passage, from accumulations of drifting ice, at the time of its formation, utilizing means of destruction for this purpose. The destruction of a jam which had formed is more complex owing to the compaction of ice in the jam and the significant increase in the quantity of ice in its body.

In the question of destroying the jams, the time factor is of great significance; therefore a primary importance is the detection of the instant of jam formation and the rapid adoption of measures for its destruction. For meeting the first requirement, we need systematic aerial surveillance in the sector where the formation of a jam is possible. The destruction of a forming jam can best be realized with an explosion under the condition of the rapid delivery of a demolitions crew by helicopter to the jam region or with the use of bombing. If the period of the jam's formation has elapsed, in conjunc­ tion with the explosions it is feasible to utilize icebreakers when the water depths and the presence of the icebreakers themselves permit such a procedure.

It is necessary to begin the destruction of a jam from its lower edge, proceeding upstream on the river. In case of a multi-branch channel, we first destroy the ice cover in the main branch, then in the secondary ones. The initial destruction of a jam in a secondary branch leads to a reduction in the water level in the main channel; as a result, the ice in it can run aground and the ice masses' density will increase; this greatly complicates the tasks involved in breaking up such a jam.

If the jam has become formed along the edge of an undisturbed ice cover, before proceeding to its destruction, it is necessary to break up this ice cover or to create a channel in it for the passage of ice having accumulated in the jam.

In case a series of jams had become formed on a river, one should pro­ ceed to their destruction from downstream; otherwise the breakup of the up­ stream jam could lead to an intensification of the downstream one. A detailed consideration of the various methods for destroying the jams has been pre­ sented in the appropriate chapters devoted to the application of icebreakers, explosions, bombing from aircraft.

Section 11. Remarks on the Organization of Jam Countermeasures

1. In organizing the combatting of jams, we should keep in mind that the use of bombing, explosions and artillery bombardment is extremely unde­ sirable owing to the tremendous harm inflicted by these methods on the fisher­ ies economy and the risk of causing damage to structures and populated points.

- 23- The application of these measures can be recommended only in unusual cases. The principal method of avoiding the use of any kind of explosives is the or­ ganization of precautionary operations for avoiding the jams.

2. Any measures for combatting ice jams should be planned and conducted with the participation of the specialists and hydrologists working in the local organizations of the Gidrometsluzhba (Hydrometeorological Service and Minvodkhoz (Ministry of Land Improvement and Water Resources), with the mandatory pro­ vision of priority. The combatting of ice jams which is conducted without con­ sidering a river's natural features and the tendencies in the process is often accompanied by the fruitless expenditure of resources and can even promote the intensification of these phenomena and their negative consequences.

3. The proper organization of all tasks is of great importance for in­ creasing the effectiveness of preventing and combatting the ice jams.

All the work must be performed systematically, must be achieved on the basis of specially conducted planning-research activities, and must be concen­ trated in permanent agencies.

4. Clear operational information is of great importance in organizing the combatting of ice jams. During the conduct of the precautionary measures, it is necessary to direct special attention to this circumstance, first having organized the reconnaissance, communications, and the processing of natural observations for predicting the individual elements (Chapter II).

5. In the conduct of any operations on rivers, connected with the dis­ ruption of its natural conditions (erection of bridges, dams, impounding reser­ voirs, rectifying operations), it is always necessary to assess their effect on the ice formation processes, attaining in the extreme case the retention of the channel's ice-passing capability in a given sector.

- 24- CHAPTER 2

FIELD OBSERVATIONS OF ICE JAMS AND DATA ANALYSIS

The effective combatting of ice jams can be conducted on the basis of taking into account the natural tendencies and is inconceivable without the organization of clear operational information reflecting the development of the ice processes on the river at the interesting period of time.

Systematic observations of the ice jams are conducted by agencies of the USSR Hydrometeorological Service. The scheduled observations include:

- more frequent observations of water levels at water-gages located close together;

_ aerial reconnaissance and ground-based investigations of the river ice conditions;

- observations of ice runoff; and

- ice-measuring surveys.

The accomplishment of the indicated range of observations permits us to organize an information service and to acquire certain possibilities for predicting ice jams, as well as to utilize the most effective means of combat ting the jams.

Section 1. Ice Jam Observations

Choice of Observation Sector for Monitoring the Water Level

In the river sector where ice jams form yearly, we set up a network of temporary gages. The number of seasonal gages should comprise 3-5 (in addi­ tion to 1-2 constantly operating or reference gages). The total length of the sector under investigation can attain 15-20 km.

- 25- It is preferable to allocate the gages at points of bends in a river's longitudinal profile. The distance between gages can be 1-4 km, depending on . the nature of the river. If the breaks in the longitudinal profile are vague­ ly expressed, the gages are arranged fairly uniformly. The gradient between the gages with open channel should comprise 0.25-0.35 m.

In the organization of the gages, attention should be diverted to the convenience of communications along shore between them and also to the presence of telephonic contact and the possibility of performing observations during the night. It is also necessary to devote attention to maintaining the in­ tegrity of gages against possible damages from ice during shifts, pileups, etc.

During the first year of organizing the observations, it is necessary to collect data typifying the morphometric and other most important natural features of the river sector. It is first of all necessary to have a plan for the sector in horizontal lines (and isobaths) and a longitudinal profile. In the plan, an indication is given of the flooding zone at various levels, cur­ rent velocities, important economic objects etc. The longitudinal profiles are plotted at various (rounded) values of water discharge.

The gage data must be expressed in a given elevation system. On the initial occasions, it is possible to establish the gage data by the technique of "water levelling." It is desirable to choose a standardized datum level for all gages. This avoids many errors and facilitates processing the observation­ al data.

The extent of detail or the number of periods of observations of the levels is determined by the type of fluctuation of the level itself and by the development of ice phenomena in the sector. Prior to the beginning of move­ ments, double-shift observations can be conducted on the level at all gages (0800 - 2000 hours). From the instant of the starting of movements, the num­ ber of observation periods increases to 4-6. Subsequently the observations are conducted at least every 3-4 hours and sometimes more often. When the level reaches dangerous elevation marks, hourly observations are required. At all gages, the level should be measured at the same time. Observations of levels at the temporary gages are discontinued within 2-3 days after final clearance of ice from the river.

Aerial Reconnaissance and Ground-Based Investigation of a River's Ice Condition

Aerial reconnaissance flights provide information concerning the ice conditions of the main rivers in a basin over a considerable distance. The optimal flight speed is 100-140 km/hr, with flight altitude of 400-600 m. It is preferred to conduct the overflights downstream— thereby it is easier to develop a concept of the state of the opening process.

- 26 - The ice conditions are portrayed on a large-scale map of the river with special symbols; other data are recorded in the flight log. During aerial reconnaissance, it is very important to have the proper control tie with the terrain; therefore in difficult cases, one must establish the time of the aircraft's position over various orientation points (bridges, river deltas, large populated centers, etc.).

In all during the period of ice opening, 3-5 flights are conducted. The first flight is made when the ice movements begin on a river. At this time it is important to establish the sectors having hummocky ice (location of fall ice jams), width of open shore zones, location of large leads and open sec­ tors. Later on the flights are conducted every 1-3 days. The principal re­ sult of aerial reconnaissance is the information gained about the boundaries of the sectors where at a given time, ice movements, jams, and ice passage are occurring. Specifically the indications of ice jamming (from below upstream) are: through cracks — fields and large floes -- large hummocks, and then small ones — compact ice passage and moderate ice passage. At points of in­ tensive hummocking, there is much pulverized whitish ice, while the surface of the ice cover usually has a dirty bluish hue. The heaps of ice at the banks testify to the drop in the level during shifting of an ice jam or its rupture.

The shore studies are conducted directly on the jammed sector of the river under study for collecting detailed information concerning the features involved in the process of opening and jamming. Helicopters are employed for this purpose. During the investigations, on the chart blank we record: open zones near shore, type of ice cover's surface (hummocks, fissures), position of jam, ice pileups at the shores etc. We also tabulate the speed of ice movement and the concentration of ice passage.

Observations of Ice Runoff

These observations are conducted for acquiring data on the amount of ice transported by the current to the jam. The line of observations is chosen 2-4 km above the jammed sector (outside the backwater limits). The observa- tion point is set up on a high bank.

Ice runoff is computed based on the curve of ice discharges and on ob­ servations of the concentration of ice passage. The output of ice is obtained as the product of four co-factors

= HhA B^, 3* where W = density of ice passage in fractions (proportion of river surface mantled with drifting ice); hA = average thickness, m, of drifting ice; B - width of river, m; and2T= average rate of ice motion, m/sec. At constantly varying density of ice passage, during the daylight hours it is necessary to conduct 4-6 measurements of the discharges. At slightly varying density of

- 27- ice passage, the number of measurements can be reduced to 2-3. The density of ice passage is pinpointed fairly often, i.e. every 1-2 hours.

Based on the measurement data, we construct a curve for ice discharge q = f(v^); aided by this curve, we compute the ice runoff for individual time spans, i.e. 6—hour, semidiurnal, diurnal, and so forth.

Ice Measuring Surveys

During the ice-measuring surveys, we measure thickness of the ice cover, thickness of ice buildups in the jam, height of hummocks and ice pileups on shore, etc.

We can differentiate a facilitated ice-measuring survey which is con­ ducted along the river channel line and a continuous survey (more exactly, a survey based on closely spaced cross sections).

The facilitated ice—measuring survey is conducted prior to opening, on a considerable expanse of the river for determining the amount of ice in the channel and the disclosure of possible jamming locations. Distance between measurements is determined by the relief complexity of the ice cover. With a relatively smooth ice cover, the measurements are made every 0.5-1.0 km, while in case of large hummocks, the data are taken every 200-300 m.

Directly in the jammed sector, the ice-measuring survey (light-duty or continuous) is conducted during the jam's existence. The distance between the cross sections is 100-300 m; the number of measuring points on the cross sections ranges from 3-4 to 7-10.

We should reckon with the fact that operations on ice during jams in­ volve a risk for the personnel and especially during ice pushes. In connection with this, it is necessary to observe the maximal safety regulations; spe­ cifically, extensive use should be made of helicopters.

Additional Types of Observations

Supplemental observations are needed for analyzing the jam-formation process: over the water flow rates, temperature of water and air, precipita­ tion. These observations are usually conducted in an operating hydrometeoro­ logical network.

It is particularly necessary to take observations of the effectiveness of methods utilized in combatting the ice jams. Here we include a description of the combatting techniques, expenditure of work time, cost of operations and so on.

Special attention is directed to the variation in the pattern of the level and in the ice conditions having occurred as a result of adopting the combatting measures.

- 28 - Remark. The observations of the ice dams do not differ in any way from observations of the jams and are conducted on the same scale.

Section 2. Data Processing of Ice Jams

The observational data for the processes of ice jam formation are in­ corporated in the form of a technical report for each winter season separately and include:

1. Tabular data:

a) Tables of water levels; b) Tables of measured ice discharges; c) Tables from calculation of ice runoff; d) Water and air temperature tables; e) Report including results of ice-measuring survey; f) Tables of water discharges; g) Tables embodying data on location of ice edge, density of ice passage and river width at edge.

2. Graphic Materials:

a) Detailed plan of jammed river sector (in horizontal lines and isobaths) with indication of location of gages, range of ice runoff observations, and also of the main orienting points (in­ flowing rivers, roads, bridges etc.); b) schematic plan of the river with results of ice-measuring sur­ vey where we also reflect the allocation of cross section, sites of ice pileups, hummocks, etc.; c) composite graph indicating fluctuation in water level for all gages in absolute elevation marks (or above a standard plane of the graph's zero point). In this same graph, we portray the pattern of air temperature based on scheduled observations, semidiurnal values of ice runoff, density of ice passage and ice phases. The time scale adopted is fairly large; d) a recorder chart of the river sector, with ice conditions. Depending on the change in ice conditions, the number of charts will fluctuate from one every 2-3 days to 5-6 per day;^ e) charts with ice conditions on the main rivers of a basin, based on data from aerial reconnaissances and en route observations; f) longitudinal profile of a river based on data from an ice measuring survey. On the profile, we show such data as thick­ ness of ice and slush accumulations, height of hummocks and pileups on shores, etc.; and g) longitudinal profiles of river’s water surface at typical mo­ ments: prior to ice push, at beginning of ice passage, at ad­ vent of maximal level, during breakup of jam, after breakup of jam, etc. For facilitating the analysis, 3-4 profiles are ac­ comodated on one graph.

- 29- Section 3. Ice Jam Forecasting

One of the techniques of combatting jams is their timely prediction; this permits one to organize in advance the adoption of appropriate measures of combatting the jams.

At the present time, a fairly complete concept exists concerning the conditions involved in the formation and breakdown of jams, concerning the pressure created by them, and the factors determining the maximal jam-related level. We are also aware of the morphological features of channels favoring the formation of jams and determining the possible sites of their formation (Chapter 1). In most cases, however, a predicting the location of the jams' formation is very difficult. In this respect, the most indefinite locations of ice jam formation are the transition sectors from shallows to pools. This is explained by the fact that on a river stretch which is uniform in morpho­ logical features, among the many sectors of transition from a shallow to a pool, there also are those in which the formation of a jam is equiprobable based on dynamic-morphological and climatic conditions.

The prediction of a jam's formation (whether it will or will not occur) can be formulated based on intensity in rise in water level prior to the be­ ginning of ice movements, based on using the data from many years' observa­ tions and a consideration of analogs. In this connection, for forecasting the formation of a jam, it is not necessary to know the actual value for the intensity in water level rise but only the probability of exceeding a certain known limit of this level. Will an intensity in level develop? In practice this limit is often determined based on the anticipated conditions for the melt water runoff from the basin's surface which are known with a greater timeliness than the intensity for the rise in water level.

The prediction of the probability of a jam's formation on opening of a in a number of cases can also be based on allowing for the maximal water level during the initial period of complete freeze-up [48]. If the freeze-up in the sector occurs at a high level, the cause of which is often provided by the damming type occurrences, a thicker ice cover is formed at this time. A later opening of such a sector at a location with thicker ice creates con­ ditions for the formation of jams on rivers, flowing mainly from south to north.

The sites of an ice jam formation comprise one of the most important factors determining the height of the jamming-type rise in water level at a given point above the jam. For the river sectors with significantly incon­ stant points of jams' formation, one can never obtain a satisfactory depend­ ence of the jam—related rise in water level on the decisive factors without considering the points of the ice jam formation.

The investigations of the possibilities of predicting the locations of ice jam formations at least on the rivers most threatened by jams would have

- 30 - required tremendous efforts owing to the extremely great complexity of the natural studies necessary which would have to be conducted over an adequate series of winter-spring seasons.

Nevertheless in all cases it is necessary to have clearly formulated operational hydrologic information. On its basis, we can judge the location of an ice jam, the time of its breakup, rates of ice masses' shifting, and so forth. We often manage to evaluate roughly the extent of the anticipated rise in level.

The question always arises first: where is an ice jam located right now? The answer can first of all be obtained by studying the river. However it is not always possible to do this (e.g., at night, in the absence of roads ánd transportation, during weather unfit for flying); therefore in difficult cases, the location of a jam can be established by analyzing the curves re­ flecting the fluctuation in levels, and even better— in the longitudinal pro­ file of the water surface. In this connection, a number of typical cases is possible.

1. There is one water gage. The formation of an ice jam below the gage is indicated by an abrupt rise in the level (at nearby location of the jam). The length of the sector (km) in which the effect of pressure from the jam is exerted roughly equals 1.5 ¿XH/i (where ¿ H = rise in level, m; i = gradient in parts per thousand).

2. There are two water gages. Formation of an ice jam between gages whett placed relatively close together leads to the situation that at the upper gage, the level rises and at the lower one, it drops slightly. We can some­ times judge the origin of a jam at considerable distance between gages based on a decrease in the ice passage density at the lower gage (with allowance for the time needed for catching up).

3. There are several water gages located close together. The location of the ice jam is determined from the longitudinal profile of the water sur­ face: it coincides with the steepest sector of the profile. The maximum rise in the level is recorded at the point where ice hummoeking occurs at a given time.

Secondly the question arises as to when the ice jam becomes formed, specifically when does the maximal level arrive? Usually the jam develops at the time of the inception of large-scale ice passage over a river sector which is considerable in extent. The ice jam sometimes occurs in the lower part of a sector which had previously become opened. At this time, the moment of the jam's formation coincides with the arrival of large ice masses from upstream.

- 31- Section 4. Predicting the Strength of Ice Jams

The question concerning the value of maximal jam-related level (or strength of a jam) is most important in the forecasting of jams. At the present stage, we are able to speak of some kind of substantiated prediction of a jam's strength for those places where the jams form constantly. These are mainly sectors of a general reduction in the river's gradient and of morphological anomalies.

For the lines of direction located in the zone of pressure from the jam having a formation site unvarying from year to year, we can establish prognos­ tic relationships between the maximal level and one or two decisive factors. Depending on local conditions, such factors can be:

1. Quantity of ice in river channel at outset of opening. In place of the volume, we can also use such parameters as ice thickness, sum of negative air temperatures, etc. The indicated types of relationships occur for rivers with significant year-to-year fluctuations in the amount of ice in the river channel, which are typical for regions with a moderately cold winter; e.g. they were obtained for Daugava River at the city of Yaunelgav.

2. The intensity of the flood stage which is typified by the rise in level during the ice debacle. Relationships of such a type are possible for the Dnepr, Neman, Visla and other rivers.

3. Negative temperature during the river's opening.

4. Intensity of warming equalling the sum of positive air temperatures from the time of their stable transition through 0° up to the date of ice-out, referred to the length of this period.

5. Difference between time of opening of the main river and its large tributaries.

Having a many years' series of fairly detailed observations of the hydrometeorological elements on a river, we can establish a connection between the maximal possible rise A in water level and the main jam formation factor for a given river which usually constitutes one of the factors enumer­ ated above under points 1 and 2.

It should be noted that moreover in individual years, the role of other factors can be intensified and can impair the basic relationship. In such in­ stances, it is necessary to introduce the appropriate corrections, utilizing the relationship of A H^ with the other factors.

Having such relationships of A with Q (ice volume) or 0 (inten­ sity of rise in level), the additional pertinent corrections from other ef­ fective factors, based on the anticipated conditions for melt water runoff

- 32- and a weather forecast, with a known degree of accuracy, we can predict the jam-related rise in the level.

The method discussed for predicting the jam-related rises in level can yield satisfactory results, but can also overlook the features involved in the actual conditions during the current year. For the rivers or their sectors for which there are fairly detailed observational data in the winter-spring period for an extended time interval, it is possible to formulate a more vali­ dated technique for predicting the jam-related levels, depending on the con­ ditions in the development of the flood stage along the river’s length.

Thus for the Dnestr River at the city of Soroka located in the zone of pressure exerted from the constantly forming jam at Voronkovo settlement, based on the observational data for 1945-1969, it proved possible to establish the relationship of the height of rise in the water's jam-caused level to the maximal (of average diurnal values) intensity of the rise in water level a the above-lying water gages located at distances up to 600 km [16].

The timeliness of predicting the d H a -value under such a forecasting technique is determined by the time required for the advance of the edge of the river’s opening from the above-lying water gage to the line of direction under discussion and comprises several days.

- 33- CHAPTER 3

ARTIFICIAL WEAKENING OF ICE

The acceleration of the opening of river sectors for preventing the formation of ice jams involves operations on the preliminary weakening and dismemberment of the ice pack. At the initial rise in water levels and in­ crease in current velocity, the weakened ice cover breaks up and is quickly carried downstream from the jammed sector, opening a basin for receiving the ice masses arriving from the upstream sectors.

In the current practice of combatting ice jams, the following ice weak­ ening techniques are in vogue:

1. Utilization of radiation heat. 2. Sprinkling the ice with chemicals. 3. Inhibiting the accretion of ice in winter (use of thermal insula­ tion from snow, "penold", and so forth). [TN: Here & elsewhere, penold = foam icej« The employment of these methods is possible either individually or in combination. These procedures are quite effective when used in conjunction with icebreakers or icecutting machines.

The common feature of these approaches is the fact that their effect is perceptible under the application of large extents of the river, from 10 km and longer. Therefore during their utilization, a more complete mechaniza­ tion of operations is particularly important.

Section 1. Using Radiant Heat to Destroy the Ice Cover (Dusting Snow-Ice Covers)

General Concepts

The radiation technique envisages the maximal utilization of solar energy for melting the ice. The sun's rays incident to the Earth's surface are partly reflected by it and are partly absorbed. The surface albedo de­ pends chiefly on the surface color: freshly fallen snow reflects up to 90% of all the incident solar radiation; on the other hand, a water surface ab­ sorbs almost all of the impinging radiation and reflects about 10% of it; black bodies (carbon, soot etc.) completely absorb the sun's energy.

- 34- As compared with snow, ice is a more transparent material; solar energy penetrates deeply into ice and breaks it into small crystals as a result of melting the ice in the intercrystalline channels with increased salinity. Solar energy is usually absorbed by an upper snow layer with a thickness up to 6 cm. Therefore the presence of snow on the ice diminishes the receipt of solar energy on the ice and obstructs its breakdown.

Effect of Dusting on Snow, Ice and Snow-Covered Ice

The effect of dusting on snow includes an acceleration of the thawing of the darkened snow as compared with the thawing of natural undusted snow. Under the effect of solar radiation, the thawing of dusted snow can occur at negative air temperatures during the daytime. If the dusted snow thaws completely under the conditions indicated above, an increase in the thickness of ice cover is possible owing to the freezing (on the ice) of water from the thawed dusted snow. In case of precipitation in the form of snow, the dusted material turns out to be within the ice beneath a layer of fallen snow an the positive effect of the dusting is reduced to zero.

The effect of dusting on ice without a snow cover includes a d srup- tion of the ice structure owing to penetration of blackening materials within it and depend on coarseness of dusting particles and ice structure. The partic­ les which penetrate the deepest into the ice are of fine fractions with partic­ le diameter ranging from 0.2-0.5 mm. Particles with diameter exceeding 0.5- 1.0 mm remain on the ice surface.

The dark pulverized particles travel more deeply into crystalline ice and less deeply into firn ice; they hardly penetrate at all into hummocky ice. After the passage of the dusting materials to the interior of the ice, its upper surface (clear of water) acquires a lighter color. However, the fur­ ther breakdown of ice continues and occurs under the effect of the dusting ma­ terials absorbing the radiation penetrating the ice. The most effective per­ iod for the thawing of dusted ice is the time with mean diurnal positive air temperatures.

The effect of dusting on snow-covered ice leads to an earlier time of melting of darkened snow as compared with the time involved in the melting of undarkened snow. As a result, the period of thawing and destruction of dust­ ed ice is lengthened; hence, there is an increase in thickness of melted ice and in the depth of the ice layer disrupted from above.

After the water absorbing almost all of the incident radiation appears on the ice, thawing of the dusted ice from above depends very little on the extent of dusting. The thawing rates of dusted and undusted ice, covered with water, prove to be almost identical. In spite of the presence of water on the ice, disruption of the ice by the dark particles penetrating it occurs. The depth of their penetration depends on depth of water layer on the ice, diame­ ter of dusting particles and ice structure.

- 35- As an advantage of the radiation method of destroying the ice, we should include the use of free powerful solar energy, possibility of working on any sectors, speed of processing and low cost of the operations. It is especially effective under conditions of long duration of the period of sol­ stice throughout the day (Arctic, Far North). A disadvantage of this method is its dependence on weather conditions (air temperature, precipitation in the form of snow) and on actinometric conditions (intensity and duration of sun­ shine) , as well as on the ice structure.

Area of Application

It is feasible to utilize the radiation method of ice destruction as an independent technique, provided that under the effect of dusting, the breakdown of ice throughout its entire thickness occurs. If this does not occur, dusting is effective in combination with the operation of icebreakers or of vessels with ice reinforcement. We thereby facilitate and accelerate the operation of ships in the ice and in addition, the possibility appears for low-power vessels not able to break up the weakened ice to operate in the ice.

We do not recommend using the radiation method of ice destruction in those sectors of rivers, bays and reservoirs, the opening of which occurs prior to the arrival of warm weather, i.e. prior to the date of the transi­ tion of the mean diurnal or daily air temperatures through 0°C.

Effectiveness of Dusting

The effect achieved by dusting is all the greater, the greater the intensity and duration of solar radiation effect, duration and temperature of warm spell preceding the opening, i.e. the period from the time of stable transition of daily (in regions with a continental climate) or of mean diurnal (in a region with unsettled weather) positive air temperatures through 0°C up to the time of the river's opening.

In the reservoirs, ocean bays and gulfs, the effectiveness from dusting is several times greater than on the rivers, owing to the presence of the crystalline structure of ice in the standing basins and because of the more prolonged warm period preceding the opening. On the rivers, the period of the most effective influence of dusting is shortened owing to the breakup of the ice cover by the flood wave. The effectiveness of dusting the snow and ice can be assessed roughly based on the coefficient representing the ratio of the absorptive capabilities of the dusted and undusted snow or ice:

K = 1-A/l-a. where A = reflection coefficient of dusted snow or ice; and a = reflection coefficient of undusted snow or ice.

The effectiveness of dusted ice's thawing from above after removal of snow from it can also be estimated in a first approximation by the coeffic­ ient *Z, indicating the ratio of thawing duration T of dusted ice to thawing duration t of undusted ice: \ = T/t. -36- Materials Used for Dusting

For dusting, use is made of dark powders, having a specific weight greater than unity and lacking any carcinogenic qualities (harmful to human health). Such materials are: coal and slag dust, phosphaté fertilizer (mineral fertilizer), foundry loam (wastes from casting industry), black sand, and also sand with a mixture of slag or coal dust, figuring 50% sand and 50% slag or coal.

In respect to their effect on ice, slag dust and phosphate fertilizer are equivalent to coal dust; therefore their use for dusting will permit a considerable reduction in the dusting expenses.

We do not recommend the use of soot or black pigment (wastes from lac­ quer-paint industry) owing to the presence of carcinogenic properties in them. Moreover, soot does not have a destructive effect on ice; the soot particles collect into granular lumps which float on the water surface and fail to penetrate the ice.

Standard Rates of Applying Dusting Materials

The maximal standard for the output of dusting materials per sq m is determined from the condition of continuous coating of the ice with the dusting materials for a depth equalling one diameter of the dusting particles. This standard can be computed with the equation

w - d 9/m2' where = weight of dusting material by volume , g/m ; d = diameter of the dusting material's particles, m. The diameter should not exceed 0.5 mm, pro­ ceeding from the condition of the dusting materials' penetrating the ice»

Depending on dusting particles' diameter at

Y = 1 t/m3 = 106 g/m3, the maximal standards for expenditure of dusting materials can be assumed as follows: At d = 0.1 mm, hm = 100 g/m2 (1 ton, lectare);

) ; d = 0.2 mm, V - 200 9/«>2 (2 " d = 0.3 mm, = 300 g/m2 (3 ) :

d = 0.4 mm, hmax = 400 g/m2 (4 ) ; and

d = 0.5 mm h = 500 g/m2 (5 ) . max

With an increase in diameter of dusting particles, the rates of material ex­ penditure and cost of dusting operations rise sharply. However the albedos

- 37- of a snow-ice cover dusted with dark blackening materials reckoning with nmax and 50% of n ^ ^ differ slightly from each other. Therefore the above-

indicated standards for the expenditure of dusting materials can be reduced to 50% of n without appreciable loss in the effect from dusting. After max heavy snowfalls, with more than 5 cm depth of newly fallen snow, it is ad­ vantageous to repeat the dusting operations. At this time, the rates for the expenditure of the dusting materials can be reduced to 15-25% of .

The quantity of the dusting particles incident to 1 sq cm of surface depending on the diameter of these particles and the sowing rates at specific weight of material equalling unity is established according to the graph (Fig. 3). At values for the material's specific weight greater than unity, it is necessary to multiply the use rates of the dusting materials in the curves by the value for the specific weight of the given material.

With an increase in diameter of the dusting particles (at the same consumption rate for the dusting materials), there is a decrease in the vol­ ume of these particles impinging on an area unit of the darkened surface and, as a result, there is a decrease in the degree of breakdown of the ice cover owing to the penetration of the blackening materials into the ice. It is necessary to resort to an increase in diameter of blackening materials in the case of conducting the dusting from a great height (20-50 m and more), causing the dispersion of the blackening Material over a considerable area beyond the limits of the intended dusting course (sectors of rivers with high banks and other protruding objects preventing the descent of the air­ craft to 5-10 m) .

The minimal standard application rates for the dusting materials established on the basis of experimental operations should not be less than the following values:

At d = 0.1 mm, h . = 5 0 g/m2 (0.5 tons/hectare); mm d = 0.1-0.3 mm, h . = 50-100 g/m2 (0.5-1.0 ton/hectare); min d = 0.1-0.4 mm, h . = 150-200 g/m2 (1.0-2.0 tons/hectare); and min d = 0.1-0.5 mm, = 350-400 g/m2 (3.5-4.0 tons/hectare) .

Dusting Periods

The dusting periods depend on air temperature and falling of precipi­ tation (snow). Dusting should be performed after the completion of heavy snow falls in the spring at air temperature excluding the freezing of ice from above, as a result of the freezing of water, from the thawed darkened snow, on top of the ice.

- 38 - The periods of dusting operations (without allowing for the time for performing the work) for regions with markedly continental and continental climate can be assumed from the time of permanent transition of positive di­ urnal air temperatures through 0°C in the spring; for the regions with un­ settled weather characterized by frequent alternations of coolings (mean diurnal temperature less than 0°C) and warmings (mean diurnal temperature higher than 0°C), the dusting season can be figured from the time of perman­ ent passage of mean diurnal positive air temperatures through 0°C in spring.

Precipitation in the form of snow having fallen after the date indica­ ted exerts almost no negative effect on the darkening (dusting) operation in view of the rapid disappearance of snow (in 1-2 days) under the influence of solar radiation at positive air temperatures.

The scheduled dusting times should be established on the basis of con­ ferring with the weather forecasting center. Under the condition of settled anticyclonic weather, one can even perform dusting prior to the passage of air temperatures through 0°C.

Fig. 3. Logarithmic Curves Indicating Dependence of Number of Particles Incident Per sq cm of Dusted Area on Sowing Rate (g/m2) for Various Diameters of Dusting Particles. ^ Key: 1. Number of particles per sq cm; and 2. n, g/m .

We do not recommend dusting a snow-ice cover in the late periods, at the peak of its intensive thawing or during the presence of water on the ice The intensively thawed surfaces of the undusted dsnow and ice will have al­ most the same absorbing capacity as the snow and ice dusted at this time.

Location and Dimensions of Dusting Courses

If the radiation technique of disrupting the ice is used as an inde pendent method, the routes for the dusting are arranged in the same way as the routes for the icecutting machines (Chapter 4). The width of the dusting

- 39- strips depends on the type of aircraft used to perform the dusting of the snow-ice cover, or depends on the type of duster mounted on the truck or cross-country vehicle.

When dusting from a type YAK-12 airplane, the width can be assumed to equal 2.5-3.5 m, while from a type AN-2 airplane, the width is 8-10 m.

If* the radiation method of destruction is used in conjunction with the operation of icebreakers or ships with reinforcement against ice, the dusting routes are arranged along the icebreaking routes (Chapter 4). Width of dust­ ing strips is assumed to be no narrower than two widths of the icebreaker when dusting from a type YAK-12 airplane or 8-10 m when dusting from the AN-2.

The preparatory tasks include:

a) layout of the dusting routes and their tying in to the locality by markers visible from the air;

b) selection of local airfields or temporary sites from which dusting can be performed; and

c) the transportation and sifting of materials for obtaining particles of the required coarseness.

The local airfields or temporary landing sites are located near the river, at a distance of 20-25 km apart. Their selection is achieved by. local branches of the Civil’Air Fleet.

The screening of the dusting material is performed through a sieve in the form of metal screens having an aperture size up to 0.6 mm. The sorted particles with size larger than 0.5 mm are poured into a standard ball mill and ground.

The storage of the dusting materials is accomplished in specially con­ structed warehouses of the simplest type, e.g. under a canopy to avoid their freezing together and compaction of materials under the effect of precipita­ tion and low air temperatures.

Performance of Operations

The dusting of a snow-ice cover can be performed from type YAK-12, AN-2 and LI-2 airplanes and also from trucks specially rigged for dusting work. The utilization of aviation permits the dusting to be done quickly over large areas, situated tens and hundreds of km from populated points.

The YAK-12 aircraft have a cargo capacity of 0.3 t, flight speed of 130 km/hr and can be employed in dusting the sectors closest to the airfield. When dusting from a height of 5-10 m, width of dusted strip proves to equal 2.5-3.5 m, while the standard use rate for dusting materials with particle diameter ranging from 0.1-1 mm at one pass of the airplane is 30-40 g per sq m.

- 40 - The AN—2 aircraft have a cargo capacity of 1.0 ton, flight speed of 160 km/hr and can be utilized in dusting the sectors at a distance of 20-30 km from the airfield. When dusting from a flight height up to 10 m, width of the strip dusted equals 8-10 m.

In case of the location of a sector to be dusted which is more than 30 km away, it is efficient to perform the dusting from an LI-2 airplane having a cargo capacity of 2.0-2.5 tons and a flight speed of 190 - 200 km/hr. At a flight height of 7-25 m, width of dusted strip comprises 15-20 m; during one pass, the dusting rate reaches 10 g per sq m.

With an increase in flight altitude, the dusting rates decrease while the width of strip dusted increases. In case of repeated operations caused by heavy snowfalls, it is feasible to perform the dusting from a greater height than indicated above, in order to attain a lower rate of expending the dusting material.

It is better to conduct the dusting during calm weather to avoid the drifting of the material, by the wind, beyond the limits of the planned route. The early morning hours are the most favorable ones for dusting. The cost of the dusting operations depend on the dusting rates and has been indicated in Table 1 below.

The steps involved in dusting a snow-ice cover are as follows. We first perform a single dusting of the route over its entire length. We proceed to the repeated dusting, necessary for attaining the planned rate fof sowing the dusting materials, only after the completion of the single dusting over the entire length of the planned routes. With such an organization of the dusting tasks, we achieve a more uniform and rapid thawing of the snow over the entire sector which is being treated and in addition we can curtail the negative effect of fallen snow on the dusting influence.

The monitoring of the dusting tasks is conducted on a daily basis, especially if these operations are being conducted for the first time. On the last flight of the airplane, the work supervisor examines all thevork performed during the day and after the airplane has landed at the airfield, he points out any errors that may have been made and together with the pilots, he draws up a plan and scope of work for the next day.

After the completion of all tasks on dusting, acceptance of the work _ is formalized, at which time, we establish the conformity of the accomplished and planned dusting routes, and the rate of expending the dusting materials.

Section 2. Chemical Destruction of Ice Cover

General Concepts and Materials Which Are Utilized

The use of chemicals for weakening the strength and destroying the ice is based on the property of certain chemicals to form, with ice, mixtures which have a melting point which is lower than their constituents. A list of such substances has been given in Table 2.

- 41- Table 1

D usting D usting Dusting D usting rate C ost rate C ost rate Cost rate C ost (kg/ha.) (mbles/ha.) (kg/ha.) (rubles/ha.) (k g/h a.) (rubles/ha.) (kg/ha.) (rubles/ha.)

100 1.0 300 2.3 750 5.4 1500 11.0 150 1.35 400 3.0 900 6.3 2000 14.5 200 1.6 500 3.7 1000 7.2 2500 18.0 250 2.0 600 4.5 1200 9.0 3000 23.0

Table 2

E lectrical Melting point Cost of technical grade Name of concentration of mixture ( t/ruble) chem icals (%) (°C ) 1st grade 2nd grade

Sodium chloride 22.4 -21.2 10 — (table salt)

Potassium 19.7 -11.1 13.6 h chloride

Ammonium 18.7 -15.8 90 80 chloride

These salts are stable in air and do not require any special safety precautions.

After application of the above-indicated chemical substances to ice, some of the ice converts to a solution. The nature and extent of the ice dis­ integration depend on type of chemical utilized, its coarseness, rates of dusting, and also on the ice's temperature and structure.

Under the effect of the pulverized chemicals, the ice thaws in a uni­ form layer with respect to thickness, from the top down. Upon the application of chemicals to the ice in the form of separate lumps, they penetrate into the ice, forming vertical sinuous channels. The ice acquires a porous form

- 42- with strong ice arches. At this time/ both the process of decrease and in­ crease in ice strength develops. The ice's strength decreases owing to a dis­ ruption in the monolithic state of ice because of the channels which have formed? however, with expenditure of heat for thawing the ice, the strength of the remaining ice arches in the channels increases.

The advantage of this technique includes the rapidity of the action of chemicals 'on the ice. Under natural conditions with a crystalline ice struc­ ture and positive air temperatures, the salt lumps with granularity ranging from 2-2.5 cm to 4-4.5 cm within a day after their application to the ice, can seep into it for a depth between 20 and 70 cm.

Among this method's shortcomings, we should mention the high cost of the materials, reduction in the method's effectiveness owing to the salts1 solubility in the presence of water and snow on the ice, and also of water interbeddings within the ice.

Area of Application

As an independent approach, it is feasible to utilize the chemical method on a limited area for the local destruction of ice, in view of the high cost of the operations. (For example, for the purpose of continuous melting of ice for its entire depth and the formation of a through lane (open zone). This method should ordinarily be regarded as an auxiliary one and we recommend employing it in conjunction with the operation of icecutting ma­ chines on river sectors with increased ice thickness (ice thickness exceeding the length of the cutter) and with inclusion of many logs and other solid ob­ jects, and also at the points of intersection of icecutting routes (Chapter 4) .

Dusting Seasons

The appropriate dusting periods depend on type of ice surface (pres­ ence of water and snow on ice) and on air temperature. To avoid the freez­ ing (at negative air temperatures) of the through trenches (having formed under the effect of chemicals) in the ice and the dissolving of these sub­ stances in the snow or water present on the ice, the dusting should be done during positive air temperatures and the absence of snow and water on the ice surface. This occurs at the time of final passage of diurnal air temp­ eratures in spring through 0°C or after separation of ice from the shores and the disappearance of water from the ice, i.e. 2-3 days prior to ice-ou

Should snow be present on the ice, the spreading with chemicals can be performed along the routes which have first been cleared of snow with a bulldozer.

Standard Application Rates

The rates of applying the chemicals for continuous thawing of ice (without ice arches) should be assumed to be 7-10 times less than the weight of the ice subjected to melting. The amount of melted ice (ccm) relating to

- 43 - 1 kg of chemicals as a function of ail* temperature has been shown in Table 3*

Table 3

Q T yp e of Volume of melted ice (cm ) chem ical at ice temperature (°C) -20 (g) -5 •10 •15

P otassium 10.3 4.7 chloride

Ammonium 14.0 7.1 4.8 chloride

Sodium 12.2 6.7 4.7 3.7 chloride

In case of dusting during warm weather with stable positive mean diur­ nal air temperatures, the action of chemicals on the ice increases and the rates of applying the chemicals can be reduced by roughly up to 50$.

Performance of Tasks Involved in Dusting Ice with Chemicals

The width of strip being dusted can be assumed to equal that of the icecutting route (0*3-0*4 m) when dusting with trucks, or 2*5-3#5 m when dusting from the YAK-12 aircraft, yielding the least width of strip as com­ pared with the other types of aircraft* With utilization of aviation, we ob­ tain an increase in the extent of mechanization of operations but the expendi­ ture of chemicals increases owing to the sprinkling of an area outside the limits of the icecutting route's width*

The procedure used for strewing the chemicals from airplanes is the same as during dusting with blackening materials* If the chemicals have a white color, they are first mixed with dark pulverized substances to create a mixture visible on the ice after the application. The rate of applying the blackening agents can comprise 5-10 g/m2 *

Section 3* Inhibiting Ice Accretion in Winter

If we retard the ice growth during the winter, up to the time of open­ ing, in a given river sector the ice has a lesser thickness; this accelerates the natural breakup and facilitates the conduct of operations on the artifi­ cial destruction of ice by any of the techniques which are employed. In this way, in the sector for conducting the precautionary measures on hastening the opening, in any case it is advantageous to have thinner ice* We can retard the ice accretion by creating an appropriate heat-insu­ lating layer on its surface* Snow and foam ice can be utilized for developing an insulating layer*

- 44- In the first instance, during vinter it is necessary to strive for the development of the deepest possible snow cover on the river. For this purpose, we can utilize the installation of various types of the simplest obstacles made from available materials favoring the accumulation of snow. For this same purpose, we can use the mechanical pushing of snow from the banks onto the ice (for instance, with bulldozers). In the development of heat insulation from snow, we should pay special attention to selecting the times of starting the operations' in order not to overload an ice cover which is not yet firm; this would lead to wetting the snow by the upwelled water and to the formation of firn ice<- The cheapest heat-insulating material suitable for inhibiting the ice's accretion is foam ice. Foam ice is made from water mixed with a foaming agent and air in a special installation. Freezing at negative temperatures, the foam changes to foam ice. The foam-applying operation can be completely mechanized. It should be pointed out that foam ice exists only at negative temperatures; therefore we do not recommend using it in regions with an unsettled winter. The properties of foam ice and the technology of its production and ap­ plication have been explained in detail in "Provisional Instructions for Appli cation of Foam Ice As Insulation Under Severe Climatic Conditions".

- 45- CHAPTER 4

MECHANICAL DESTRUCTION OF ICE

The acceleration of the rivers* opening can be attained with the aid of mechanical dismemberment of the ice cover# At the first rise in water levels and increase in current velocities in the river, the dismembered ice cover breaks up and floats downstream, opeing the possibility for the unob­ structed passage of ice masses arriving from upstream#

The mechanical destruction of ice is done with icecutting machines and icebreakers# In addition, icebreakers can be utilized for breaking up jams which have already formed#

Section 1# Icecutting Machines and Their Characteristics

Icecutting machines of various types and capacities are utilized when the use of icebreakers is ruled out because of shallow depths, or in combina­ tion with other means of destroying the ice (with the same icebreakers, with use of dusting and so on)•

Icecutting machines are commonly of three types; with gangs of cut­ ting teeth or bars from cutting machines; ice milling tools with a vertical cutting arrangement; and ice planers#

The icecutting machines equipped with chains or bars have a fairly simple design and high output rate# Several types of such machines have been built (based on the "Druzhba** [Friendship] gasoline-powered cutting tool# the DLN-1 and LM-3 machines; the Ustinova-Tyukhtin machine)# Experience has shown, however, that the narrow slots cut by these machines in the ice quick­ ly close up again and the ice freezes together, restoring its strength# There­ fore the icecutters of such a design are of little suitability for operations aimed at avoiding ice jams# The ice-milling machines with vertical knife- or cam-type cutters (LFM-GrPI-34 and LFM-GPI-41, the CHMP towed machine and its improved model being manufactured by the MRF (Ministry of River Fleet) Lim- endskiy Plant) do not cut a narrow slot in the ice, but rather a trench not reaching the water or, if required, a through lead with a width of 25-45 cm#

The ice planers, in distinction from the machines mentioned above, do not cut or mill the ice but shear it in the form of a wedge oriented

- 46- horizontally and towed like a plow behind a floating vehicle or amphibious tractor* Moving over the ice at high speed, such a setup leaves a furrow behind it, lacking 15-20 cm of reaching the ice's lower surface. Experiments are underway for making through leads (openings) in ice with the aid of plan­ ers. The ice planers are not yet made under factory conditions but their de­ sign is so simple that they can be made by an economical method in any work­ shop. The utilization of ice planers has not yet exceeded the experimental stage•

The productivity of the various means of mechanical destruction of ice has been shown in Table 4«

Area of Application, Advantages and Disadvantages of Icecutting Machines

As a means of avoiding ice jams, icecutting machines have a number of significant advantages, including:

— the possibility of implementing measures on nonnavigable water bodies or river sectors to which access by icebreakers is either difficult or impos­ sible;

— the possibility of the breakup of thick ice in which the river—type icebreakers are powerless;

_the possibility of the destruction of the ice cover not only in a navigable channel but also in the shoals^ usually occupying the predominant area;

— the possibility of transferring the equipment from one river basin to another overland; this permits an appreciable reduction in equipment in­ ventory, concentrating the machines in the sector most dangerous according to forecasts;

— no harm to the fisheries industry is involved;

_the possibility of performing the work over large areas;

_reliability of effect and independence of the results from weather conditions; and

_the opportunity to perform the tasks directly before ice-out time.

However, along with the advantages, the utilization of icecutting ma­ chines does have a number of significant shortcomings*

These include first of all the impossibility of employing such ma­ chines for the elimination of jams which had already become formed during the spring ice passage*

- 47- T able 4

Speed during operation W idth o f on ice of varying trench Productivity Productivity T y p e o f So u rce M ethod o f P ow er Servicing (m /h r) (O pen (m $ /h r) c u t o f d a ta destroying ice (hp) p e rso n n e l 0 .5 1.0 1 .5 le a d ) (m ^ /h p hr)

0.05 i 7 3 2 0.3 - 0.7-1 Through channel Standard time rates foi Manual cutting of channels ice cutting and freez­ ing operations

70 3 60 30 - 0.25 0.1 3 Through channel Standard time rates fo; Towed icecutting machine made by ice cutting and freez­ Lidmendskiy Plant of the Ministry ing operations of River Fleet 74 2 160 100 70 0.35 0.4 14-45 Through channel Factual data accordin Self-propelled ice-milling mach­ to White Sea-Onega ine, LFM-GPI-41 Shipping Company

Ice planer with amphibious trac­ 90 2 4500 2000* - 0.6-1.5 4.5-14 200-600 Trench lacking 20 cm Experimental data tor, TP-90 of reaching the lower surface of ice

Ice planer with floating tow 200 2 12000* 5000* - 0.6-1.5 5.4-16 500-1600 Trench lacking 20 cm Estimation vehicle, GT-T** of reaching the lower surface of ice

* Approximation. ** Calculation based on engine power. These machines are suitable only for precautionary preventive measures since with their aid, we can never create the extensive water surfaces free of ice, constituting a reliable guarantee against the formation of ice jams but we can only weaken them or, in the optimum case, we can separate the ice cover into sections. It is impossible to employ most of the icecutting machines on thin ice which covers many rivers. The minimal thickness of ice for the ice planers comprises 30-35 cm while for the LBM-GPI-41, it is around 25 cm.

Analyzing the advantages and inadequacies of the icecutters, we can conclude that their application for the prevention of ice jams is possible in all cases when the thickness and strength of the ice cover are adequate and the latter can withstand the weight of the equipment.

Application of Icecutting Machines In Combination With Other Equipment

In those cases when thé plan for the conduct of the anti-jam measures envisage the mandatory development of extensive open leads with water free of ice, it is necessary to combine the operation of icecutting machines with the utilization of icebreakers. It is especially important to note that in this case, the thickness of ice surmounted by an icebreaker during continuous move ment increases by 2-3 times.

The ice planers cut furrows not reaching to the lower surface of the ice. Experiments have indicated that even at a negative temperature, these furrows melt through in 2-4 weeks, converting to through channels separating the ice pack into sections. If we combine the operation of ice planers with the artificial acceleration of thawing by chemical methods or by way of black ening, this process can be speeded up appreciably. The chemical and blacken­ ing agents can be applied directly into the trench, after having mounted the duster on the ice planer's frame.

- 49- Direction of Icecutting Routes

The direction of icecutting routes is established depending on the di­ rection of cracks originating in an ice cover during the ice pushes and the beginning of ice debacle. It is more advantageous to cut the ice cover in a direction difficult for the natural breakdown of ice. On rivers, during movements, the ice cover is broken chiefly in a direction across the river; therefore the cutting of the ice cover can be conducted advantageously along routes oriented along the river. In a reservoir, this is accomplished better along the routes oriented in two mutually-perpendicular directions at an angle of 45° to the direction of river flow. For facilitating the displace­ ment of the ice cover during pushes, the ice cover of the main river is sep­ arated from the ice cover of the channels (at the inlet and outlet from them) and from the ice cover of the tributaries if they break up later than the main river.

In the river sectors when the ice cover up to the time of ice-out is maintained in an undisturbed state, it should be cut over a considerable distance along additional routes directed across the river (on the pools, in place of abrupt widening of the river channel, ahead of the narrowing of the river and after it, in the region of a sharp bend, at the upper end and lower end of an island). It is preferable to make the icecutting path smooth, without projections, since the presence of protrusions in it compli­ cates the shifting of the cut fields during the movements of ice.

The number of longitudinal icecutting paths can be assigned from 1 to 3 according to river width. The ice cover is cut with a main lengthwise course located along the middle of the ice cover's width or within the limits of the navigable channel over the extent of the entire sector. On the curves and bends in a river, the number of icecutting routes should be increased to two, three and more. At points before the narrowing of a river and after it, the number of icecutting routes is established from the condition that the width of the ice cover between them constituted roughly 2/3 of the river width in the narrow place.

On a reservoir, the ice cover is cut into squares, the sides of which equal half the river width. At the places of intersection of the icecutting routes, the ice cover is cut in one direction, while in the other direction it is maintained in an undisturbed state within the limits of 2-3 widths of the icecutting track. The remaining ice bridges can be broken up later on with the aid of radiation and chemical techniques.

Appropriate Times for Performing the Operations

The periods for initiating the operations on cutting an ice cover by icecutting machines are established proceeding from the length of sector, number of icecutting tracks, number and productivity of icecutting machines

- 50 - and climatic conditions in the region of operations. We proceed to the ac­ tivities on cutting an ice cover at seasons excluding the freezing of the icecutting leads by more than 1/3 of their depth. For example, for the Northern Dvina, these seasons arrive 1.5-2 months prior to ice debacle. The tasks in cutting the ice cover are finished by the time of the permanent transition of the diurnal positive air temperatures through 0°C in the re­ gions with a continental climate or by the time of final transition of mean diurnal positive air temperatures through 0°C in the regions with unsettled weather.

On. the rivers breaking up prior to the indicated dates, the times for finishing the operations are established on the basis of forecasting the opening of these rivers.

Laying Out the Routes

The laying out of the icecutting routes and tying them in to a local­ ity are conducted in fall soon after the final freezup when the limits of the river channel are still clearly identified. In spring, the ice cover on a river and the adjoining earth surface are covered with snow; therefore a determination of the boundaries to the river channel during this period is difficult.

For laying out the icecutting routes, the width of the river channel is assumed to equal that width based on which the ice-out is accomplished prior to the freezup. Roughly within the indicated limits, there occurs the separation of the ice cover from the shores in spring. The configuration of the river channel occupied by ice passage prior to complete freezup is deter mined on the basis of observations of the autumn ice passage during the ice aerial reconnaissances and the shore-based overland studies.

The icecutting track is marked by indicators in the form of several intertwined branches of coniferous and other trees. These markers are placed at a distance of 100 to 500 m apart depending on length and width of the sector.

The preparatory tasks include verifying the correlation of the ice­ cutting tracks to the locality, and, in case of necessity, the placement of new markers at the locations of their absence and also a measurement of the thickness of snow-ice cover every 100-300 m over the entire length of the icecutting route.

On an ice-measuring survey, we perform the correction of measures for avoiding the f donation of springtime ice jams; we determine the boundaries of the sector with the cutting of the ice cover by icecutting machines; in the sectors where the icecutting machines cannot be utilized (slight ice thicknesses, frozen-in logs and other reasons); other methods are indicated for destruction (radiation, chemical, ice breaking operations and manual).

- 51 - Section 2. Using Icebreakers to Prevent and Combat Ice Jams

General Information

The utilization of icebreakers can be considered as one of the effective preventive measures for avoiding ice jams. The gist of utilizing icebreakers is that with their aid, within the limits of a jammed sector, slightly above it and for a fairly considerable sector below it, we accomplish the dismember­ ment of the ice cover into separate longitudinal belts which on elevation in levels and increase in current speed break up and are quickly drifted down­ stream, opening a basin for the ice masses arriving from the upstream sector of the river. The limits of the sector in which the icebreaking operations should be conducted should be established in each individual case with con­ sideration for the actual morphological features of the channel. In any case, these sectors are measured in tens of kilometers.

Icebreakers can be applied successfully also in the breakdown of ice jams which have already become formed.

The disadvantages of the icebreaking technique are: the absence, in a number of basins, of adequately powerful icebreakers with shallow draft for the possibility of conducting the indicated operations and also the cir­ cumstance that although an icebreaker does break up the ice, it does not re­ move it. In addition the modern river-type icebreakers are not able to move in slush and ice dams; this can be extremely important in combatting the ice jams having formed at the site of a previous ice dam (clogging formed by slush and bottom ice).

In recent years, we have become aware of achievements in the field of the planning and construction of icebreakers which expand their capabilities significantly both for the prevention and combatting of ice jams. These in­ clude first of all the application, on icebreakers, of pumping installations with mechanical or hydraulic drive exceeding by 50-60% and more the critical ice trafficability of icebreakers and in addition improving their maneuver­ ing qualities and, in particular, completely eliminating the possibility of the icebreakers becoming beset in the ice. Secondly these devices permit us to push the broken ice under the edge of the ice cover.

At the present time, there are suggestions for the development of ice­ breaking attachments with pumping installations (PI) connecting to conven­ tional tugboats and power vehicles which sharply increase the icebreaking qualities of the latter, bringing them to the level of the icebreakers with the pumping installations of the same power as the pushing machines (power vehicles). The icebreaking attachments not having an actual propulsive in­ stallation are significantly cheaper to build and to operate than the con­ ventional icebreakers. The attachments can also push the broken ice under the edge of the ice pack.

- 52 - The basic parameters of the riverine icebreakers have been presented in Table 5.

Table 5

Parameters ot Name of icebreaker designs riverine icebreakers R~47 16 1054

Established power of main engine 600 1800 4600 installation (hp)

Design craft (m) 1.8 2.4 3.5

Critical ice trafficability at v « 3 kg/hr: without control device (cm) 31 32 45 with control device (cm) 40 -- 66

Application of Icebreakers for Avoiding the Formation of Ice Jams in Springtime

The destruction of an ice cover by icebreakers or vessels is mandatorily performed upstream of the river and by at least two icebreakers or vessels with reinforced hulls for extending aid to each other in the case of neces­ sity .

The operations on the destruction of an ice cover by icebreakers, ves­ sels with reinforced hulls and icebreaking attachments are accomplished within the limits of the entire or partial length of the sector endangered by a jam, upstream of the river along the navigable channel (if depths per­ mit, also along the center of the river width), from the anchorage site of vessels during winter to a point where the vessels can take refuge during the springtime ice passage.

- 53 - The width of the route depends on the location of the jam-endangered sector along the river length. If the jam-threatened sector is situated within the branches of the river delta (for example, the Northern Dvina River), the width of the channel cut by the icebreakers or vessels can com­ prise 80-200 m for facilitating the descent of the broken ice into the sea or basin previously freed of ice. The presence of such a channel permits the icebreakers and vessels to escape into a place sheltered from the ice passage during the spring ice movements or an ice passage which has started. If the ice jam -- threatened sectors are located in all the remaining sec­ tors of the river, the least width of the tracks can be assumed equal to the Width of the icebreaker or vessel with the reinforced hull.

The operations on the destruction of an ice cover by icebreakers or vessels equipped with a reinforced hull are conducted both in autumn (or eliminating the fall ice jams, favoring the formation of the spring ice jams) and in spring. The times of starting the operations in spring are established depending on the scale of activities and the air temperature, exerting great influence on the ice strength.

It is feasible to proceed to the operations on the destruction of ice upon the arrival of positive air temperatures during the daytime hours. The most effective time for the breakdown of ice by icebreakers or vessels is the period from the time of the ice's separation from shores to the time of open­ ing. During this period (2-3 days), there is a decrease in the ice viscosity as a result of the disappearance of water from the ice, and the ice becomes weakened owing to the solar radiation penetrating into it.

In case of the destruction of ice cover in spring and the presence of spaces for the descent of ice broken by icebreakers or reinforced-hull ships, the following order of operations is adopted.

Two icebreakers or two reinforced-hull ships begin to break the ice, forming a channel, from the edge of stationary ice, moving upstream. One vessel moves ahead while the second moves at a distance from 150 to 200 m from the first along the river's length and at such a distance over the river's width so that in the ice cover located between the channels, trans­ verse cracks would develop. This distance depends on ice thickness and can be, e.g. at h = 0.2-0.3 m equal to 60 m and at h = 0.5, it can be 40 m.

The floes forming in the channel are captured by the current and drift downstream. When necessary, a further expansion of the channel is achieved from the shock effect, on the ice, of the wave action developed by the ships moving along the edge of the channel.

The channel width is assumed to equal roughly 80 to 120 m. In the sec­ tors with permanent and intensively hummocked ice or in places of transverse cracks where the ice is arranged in several layers by height, the width of channel can be increased to 200 m for convenience in operations on the

- 54- destruction of ice by icebreakers or reinforced-hull vessels while gathering momentum.

If the ice cannot be broken by icebreakers or vessels while speeding up, two icebreakers or ships are connected together and in combination ad­ vance, breaking the ice.

The order of performing the tasks in creating a channel in the ice cover during the simultaneous operation of two icebreakers or reinforced- hull ships has been indicated in Fig. 4.

II

-2 □ -4

Fig. 4. Order of Performing Work in Formation of a Channel in Ice for Preventing Springtime Ice Jams. 1- Icebreakers; 2- Ice cover broken into floes; 3- Channel in ice, free of ice; and 4- Ice cover.

Destruction of Ice Jam By Icebreakers and Vessels With Reinforced Hull

The destruction of an ice jam must be conducted by not less than two icebreakers or reinforced-hull ships so that when necessary the icebreakers or ships can extend assistance to each other.

The width of a channel in an ice jam is established proceeding from the conditions of the operating safety of the icebreakers or ships in a channel and also based on the possibility of their rapid turning and departure from the channel in the case of the irruption of the ice jam. The channel width can be roughly assumed to equal 100-150 m. The icebreakers or vessels ap­ proach the lower edge of the jam and attempt to enter the jam in its central part along the cracks or along the sectors with the least compact ice. In case of great density of the ice in the jam, the icebreakers or ships advance

- 5 5 - by rushing at the ice while accelerating. If the broken-off ice is not carried downstream but stays in place, the icebreakers or ships drive it from the channel by the current forming from the operation of their pro­ pellers.

The techniques used in breaking down ice with icebreakers or ships de­ pend on the power of the icebreakers or ships, their number and also on the density of ice in the jam.

With the same power of icebreakers or vessels, they approach the lower edge of the jam and begin to break down the ice in the central part of the jam along longitudinal channels parallel to each other (Fig. 5, a). When the length of these initial channels reaches 25-30 m, one proceeds to the elimination of the ice arches having remained between the channels and the expansion of the channel which has formed, by chipping the ice from its sides. Then the above-indicated work cycle is repeated until the breaching of the ice jam takes place.

At this time, it is necessary to carefully watch the ice conditions and especially the development of a strong current. During movement of the ice in the jam, the icebreakers or vessels should immediately stop operations and proceed to a location safe from the ice drift, in order to wait out the movement of ice in the jam or the passage of the ice upon breaching of the ice jam.

Fig* 5. Methods for Destroying Ice Jams by Icebreakers or Ships With Reinforced Hull, a- Destruction of ice along parallel channels with subsequent removal of ice from the prominence which has formed; b- Removal of ice from the jam in separate wedges; c- Laying of zig­ zag-shaped channel in a jam with subsequent removal of triangular projections; 1- icebreakers or ships with reinforced hull; 2- channels laid in jam by icebreakers or ships; 3- ice jam consisting of small blocks of compressed ice; and 4- water surface free of ice.

- 56 - If the cutting of the initial channels in an ice jam is difficult fox each of the ships, a channel can be cut as a result of the simultaneous op­ eration of two icebreakers or ships moving at an angle to each other. In this case, the ice from the jam is sheared away in the form of separate wedges (Fig. 5, b ) .

If a powerful icebreaker and several ships operate simultaneously (for example an icebreaker with a power of 2200 hp and two ships with a power of 600 hp each), the icebreaker has the problem of cutting a zigzag channel in the ice jam while the other less powerful ships have the problem of widening the channel, which has formed, by breaking off the ice from the triangular projections (Fig. 5, c).

In the case of small ice jams on small rivers when at the head of the jam, large wedged floes are located, held at the abrupt bends on the river and in other sectors, the destruction of these floes can be accomplished by the effect of a hydraulic wave developed by a conventional ship with an un­ reinforced hull. The ship is directed at high speed through open water to­ ward the head of the jam and, stopping several meters before the lower edge of the jam, it suddenly stops. The wave which has developed at this time approaches the head of the jam and can cause the cracking of floes, holding back the ice jam.

- 57- CHAPTER 5

ARTIFICIAL ICE JAMS AND STRAIGHTENING OF CHANNELS

One of the methods of combatting the ice jams is the creation of arti­ ficial ice jams at the safe locations. This is frequently associated with the construction of ice dams, varying the river flow conditions during the flood period. Such dams as earth structures of a similar type can serve as straightening structures; these are also considered in the present chapter.

Section 1. Artificial Ice Jams

General Concepts

One of the active measures of combatting the ice jams is the artificial formation of jams in those places where the floods caused by them do not cause any damage. The stoppage of the runoff of ice material provides the possibility of the normal opening and clearing of the protected sector from ice, favors thawing and weakening of the confined ice; subsequently, this facilitates its unobstructed floating downstream.

In certain cases, the artificial ice jam formation can pursue the goal of flooding a floodplain for intensifying the growth of grass and an increase in harvests.

The location for the formation of an artificial ice jam is usually pro­ vided by a river sector in the region of the river's separation into channels (branches). The multi-branch sector should be situated upstream from the jam-threatened (protected) sector and downstream from artificial structures (bridges and so forth) to avoid damage to these structures during the ice passage, by jam-type ice with increased thickness and strength.

For the formation of artificial ice jams, the following techniques can be utilized:

opening the river during low water levels, as a result of which there is an increase in the resistance to the advance of the ice passage down­ stream;

an increase in thickness and strength of ice cover up to the time of opening; and

a decrease in the ice-passing capacity of the river channel by way of an artificial narrowing of the river channel.

- 58 - Opening of a River During Low Water Levels

An artificial lowering of the water levels during opening of a river can be realized only on rivers which are subject to control.

An increase in the thickness of ice cover can be achieved by the syste­ matic clearing of snow from the ice or with the aid of freezing the ice from above. An increase in the strength of ice cover can be achieved up to the^ time of opening by safeguarding the ice in spring from destruction under the effect of positive sit temperatures and solar radiation.

The artificial narrowing of a river channel is achieved by the con­ struction of permanent or temporary facilities (ice dams).

Increasing the Thickness and Strength of an Ice Cover

The measures adopted for creating an artificial ice jam by means of an increase in thickness and strength of ice cover are conducted either in the main branch of river, if along it there is achieved the main passage of ice, of simultaneously in several branches having the maximum ice-passing capabil­ ity. The routes with increased ice strength are arranged in a direction oriented across the river at a distance about equal to half the width or to the total width of the river and mandatorily in the places of the expansion and narrowing of the channel. The width of these routes is assumed to equal roughly 0.1-0.15B. The ice cover in the upper part of the river branches under consideration is maintained in a natural state for improving the con­ ditions of the buildup of ice material during the ice-out period.

The laying-out of routes in the ice and their tying-in are conducted after the complete freezup. The clearing of snow from the routes is ac­ complished during the entire winter season after the falling of snow and also after strong winds blowing the snow from the surrounding surface in o the track. For this purpose, use can be made of conventional snowplows with the hauling of snow by trucks onto shore. If the ice cover has a hummocky surface, the track is first cleared of hummocks with the aid of a bulldozer.

In the freezing of ice from above, use can be made of the road-sprinkl­ ing machines or firefighting equipment. In case of the lack of ?ufh e q u |;J' ment, around the perimeter of the tracks, we erect snowbanks, which are then flooded with water. In the space which has been formed between the banks, we supply water with a pump from a cut hole, in a layer up to 5 cm. A±t®r the freezing of the poured water, the operation on increasing the ice thic ness is repeated until the ice thickness from above reaches 0.5-1.0 h (where h »natural ice thickness). At the points of the juncture of the ice track with the shore, the thickness of frozen ice can be increased. Moreover, the strengthened belts of ice can be anchored to the shores; for this purpose use can be made of old cables, chains, logs and so on.

- 59- For safeguarding the ice tracks against destruction under the effect of positive air temperatures and solar radiation, up to the time of comple­ tion of heavy frosts or until an abrupt increase in the duration of solar radiation, their surface is covered from above with sawdust, straw, conifer­ ous needles and with other materials.

Decrease in Ice-Passing Capability of a River Channel

The decrease in the ice-passing capacity of a river channel can be achieved with the aid of an artificial narrowing of the river channel; for this purpose we build permanent or temporary structures (ice dams). At this time, we should take into account the re-formings occurring in the navigable river branch after completion of the ice passage.

The ice levees (dams) can be situated both on a dry shore (almost every­ where) and also in the river channel in a deep location (in regions with severe climatic conditions). The ice levees should be placed in the narrow sectors of a river or in sectors where the passage of springtime ice is also difficult (e.g. in the region of a sandbank ahead of a wide pool sector, etc.) The axis of the ice levee should form, with the axis of the river streamflow, a, blunt angle in order to assure the arrival of the ice material beyond the pressure side of the levee.

The length of the levee can reach 100-200 and more meters. The eleva­ tion marker of the levee crest should be located above the flood level by not less than 0.1 of the levee’s height in order to avoid the floating up of the levee owing to the ice’s buoyancy. The width of the levee at the base should be from 10 to 20 m while in height, it should be 2-3 m less.

In the construction of an ice levee on a dry shore, along the levee’s axis we freeze into the soil bunches of logs for better adhesion of the body of the future ice dam with the ground. Then, along the perimeter of the future dam, we spread small snowbanks forming a trough into which we pour water in a layer from 10-15 cm. After the conversion of water to ice, the edges of the trough build up and the operation is continued gradually until the dam's crest reaches the required elevation mark. In the case of large dimensions of the dam, above it along its axis we set up a wooden platform with troughs into which water is supplied by a pump. From the troughs (chutes), water runs downward by gravity into the body of the dam. To avoid the freezing of hoses through which water enters the darn, we heat the water supplied by the pump, from the ice hole, to the dam. For this purpose, the water is passed through standard water-pipe clusters installed in an iron barrel in which the fire is placed. After the completion of the scheduled delivery of water to the dam’s body, the hoses are collected and dried.

For protection against the effect of the sun, before the beginning of ice passage the dam crest is covered with straw, shavings, moss or other

- 60- materials. As the practice indicates, the ice dams break up under the effect of external heat and of warm water only after the beginning of ice passage.

The head of the dam subjected to the influence of moving ice proves to be in the most stressed position. As a result of the abrasive effect of ice, the dam's length decreases. For increasing the dam's strength, brushwood is placed in the head of the dam during the freezing of ice.

The construction of an ice dam in a deep place begins with the draining of the basin in which the dam is to be situated. This is achieved in regions with harsh climatic conditions by the use of freezing operations, for the conduct of which we can utilize the instructions for icebreaking and freez­ ing operations. The ice cover at the location of the future dam is divided into freezing leads with a length of 2 m, width of 1 m and with a width of ice arches up to 1 m. The freezing is accomplished to the ground; then we freeze logs into the ground and proceed to the freezing of ice in the leads in the usual sequence.

A stratified ice cover is distinguished by great strength and is dis­ rupted under the effect of solar radiation into crystallites, with a height equalling the thickness of the water layer supplied to the body of the dam. Sometimes for greater strength, brushwood is frozen into the dam's body..

In the absence of conditions necessary for accomplishing the freezing operations, the length of the ice dam built on shore can be increased owing to the freezing of ice on the ice cover, which is afloat. This part of the ice is separated from the remaining ice cover by a through trench. The freez­ ing of ice is conducted in the usual sequence. Under the effect of its own weight, an ice "tongue" descends until it reaches the ground. The operations on freezing the ice are performed with caution in order to avoid the forma­ tion of a crack at the point of the transition of the shore ice dam to its floating part. After settling on the ground, the height of dam over its entire length is reduced to the required elevation mark. A disadvantage of the ice dam which is built while afloat is the poorer adhesion of the dam's base with the ground than in the case of building the ice dam on a dry shore.

Section 2. Channel Straightening to Prevent Ice Jams

General Information

The straightening of a channel with the aid of major permanent struc­ tures is an effective technique for avoiding ice jams chiefly for rivers flowing southward, i.e. in those cases when the reason for the formation of a jam is the inadequate ice-passing capability of a channel in the sector under consideration.

For its attainment, the straightening requires considerable capital investments. Therefore the given technique can be recommended for application

-61 in those cases when the additional capital investments required for imple­ menting the straightening operations will be regained owing to the possible loss inflicted by the ice jams on some given branches of the national economy or inflicted on private property, in the course of a standard period (10 years). In addition, it is necessary to be convinced that during the indicated per­ iod, the sector subject to straightening will not prove to be within the backwater limits of one of the reservoirs under construction.

The conduct of straightening operations with the aid of the setting up of temporary, chiefly ice, structures can prove feasible under the appropri­ ate climatic conditions guaranteeing a rapid and reliable erection of the indicated structures. Moreover the expenditures justifying the conduct of the necessary (usually annual) operations should be within the limits of the possible average many years1 loss inflicted on the national economy or on the property of citizens during ice jams.

It is also possible to have a combined solution when the permanent straightening structures during the period of passage of the springtime debacle are supplemented by temporary structures, usually made of ice.

Basic Concepts Involved in the Straightening of Channels

The basic trend in the planning of straightening operations for avoid­ ing ice jams includes the creation, as a rule, of a single-branch, rectilinear or slightly curved channel, assuring the unobstructed passage of ice. If on the basis of any given concepts, a two-branch channel is left in the straight­ ening sector, the upper part of the island dividing the channel into branches, with the aid of a special structure, should be given a configuration with a minimal frontal angle guaranteeing the smooth entry of ice masses into the branches.

The existing methods for establishing the basic dimensions of the straightening route proceed from the condition of equality of the discharges which are passed by the channel in the usual and planned condition. In the planning of a straightening course in the sectors prone to ice jamming, this requirement should be supplemented by the condition of the unobstructed pas­ sage of the ice debacle, which for the rectilinear sectors or sectors with slight curvature of channel reduces to a guarantee of the constancy of the ice-transporting capability of the flow. The latter (at constant channel flow rate) is determined by the constancy of the product of the average surface velocity over the channel*s width times the channel width at the ice debacle level.

The indicated stipulation should be supplemented by the requirement of the presence, on the entire width of straightening course, of a depth of not less than the maximum possible draft of the floes. In a first approxi­ mation, the former (with consideration of the possible overlapping of one

- 62- floe upon the other) can be assumed to be not less than two maximally pos­ sible ice thicknesses in the given region.

The width of the straightening course on the curves (bends) should be increased owing to the development of additional resistances to the movement of ice owing to the increasing force of ice friction along the concave shore and between the floes; this leads to a decrease in the kinetic energy of the moving ice and to a reduction in its speed.

The limits of the river sector subject to straightening are established by the sections, above and below which the river has a single-branch permanent channel, not causing any risks in respect to the probability of the formation of ice jams.

These sections should satisfy the conditions of jam-free passage, which is determined in a first approximation by the jam-formation criterion:

K = r/77 £ 1, here r = index of section's completeness. It is determined from the condi­ tion

H/H0 = (^/B1)r, where H » maximal depths H = depth at distance ¿3 from water edge, determining the value F S ; Bx = half-width of channel; and ^ = Y /F = coefficient of ¿ce..passing capability equalling the ratio of part of the section area (Fc where the ice moves freely, to the entire discharge section area F.

Recommended Methods of Straightening

In the straightening of a channel for avoiding ice jam formations, it is desirable to use embankments, longitudinal dams, shore revetments and other similar structures which develop a smooth course without individual protruding elements obstructing the movement of floes; otherwise, the dsngsc of the formation of ice jams develops.

The application of transverse structures, being more economical and in a number of cases more effective in respect to the influence on the chan­ nel forming processes, is permissible only at the convex shores; moreover, the structures should be oriented in a direction following the river current.

The crests of the structures should be raised above the ice passage level, as a result of which the frontal slopes of the longitudinal dams for reinforcing the banks, the heads of half-embankments exposed to the effect of moving ice masses should have the necessary reinforcement.

- 63- In a number of instances, the requirements indicated contradict those providing the optimal conditions for the effective straightening of the channel in the interests of navigation and in addition lead to a significant increase in the nonrecurring capital investments. As a result of what has been indicated, on the river sectors where the conduct of the straightening operations in the interests of navigation is not required, while the erection of permananent structures exclusively for avoiding ice jams is not justified economically or leads to a deterioration in the navigable conditions as com­ pared with the normal everyday conditions, it can prove feasible to con­ struct temporary ice structures.

In those cases when the erection of straightening structures is neces­ sary both for purposes of avoiding jams and for improving the navigating con­ ditions, it may prove feasible to construct combined permanent and ice-type structures. Here the first are built in conformity with the requirements of deepening the channel for navigation while the second are constructed pro­ ceeding from the requirement of ice passage. For example, the transverse structure is arranged in accordance with the navigational requirements while the longitudinal ice structures are built in such a way as to create favor­ able conditions for the passage of ice during the ice-out period.

The erection of permanent structures of traditional design is accomp­ lished by the methods discussed in report [44].

The construction of the temporary ice structures is conducted in win­ ter by means of their gradual layer-by-layer freezing (Chapter 5, Section 1).

- 64- CHAPTER 6

USING AIRPLANES TO PREVENT AND DESTROY ICE JAMS

Aviation can be widely utilized for organizing the combatting of ice jams and dams, and in many cases is the irreplaceable metnod*

With the aid of airplanes, we can conducts

a) reconnaissance of ice conditions over an extended length of a river in the pre-flood period and during ice-out* The investigation can be conducted both by visual observation and with the application of aerial photography;

b) delivery of personnel, equipment and materials required for the conduct of the blasting operations both on the ice cover and in the elimination ox a jam which has formed;

c) elimination of jams by bombing them from the air; and

d) destruction of an ice cover by bombing, with conduct of precautionary measures for combating the ice jams*

Section 1• Aerial Ice Surveys

Aerial surveying is the most efficient method for clarifying the ice conditions on the main rivers of a basin over a considerable expanse* Aerial surveying is especially indispensable in those cases when it is difficult to predetermine the exact location of a jam*s formation* The recorder chart of aerial ice surveying (compiled on the basis of a diagram or large-scale map of the river) comprises one of the main operating documents in assigning the most efficient measures for dealing with ice jams*

The overflight for a river for an aerial survey of the ice conditions should be conducted from above downstream* The flight speed most preferred is 100-140 km/hr at a height of 400-600 m* Under these conditions, it is easier to form a concept of the condition of the opening process and of the overall ice conditions*

- 65- Overflight downstream at 200-250 m height provides a possibility of surveying the ice conditions in detail in separate sectors of the river. In the sectors where hummocky ice builds up, we should perform flights across the river in order to determine the movement of a hummocky accumulation and the position of the slushy track.

For assessing the ice conditions and predicting the chance of jams' formation in those places where they form from year to year (estuarial and backwater jams), it is feasible to conduct an aerial ice survey in the region of the jam's formation and in the sectors located farther upstream, beginning from the time of the first ice pushes.

An analysis of such a type of photographs for a fairly long series of years provides great opportunities for comprehending the regularities in jam formation in the river region under study and will aid in developing detailed systems for counteracting the jams tinder various conditions during each year.

More detailed observations directly in a jam sector under study can be made with the aid of helicopters. Such investigations will provide detailed information concerning the features of the process of opening and jam forma­ tion in a given range.

It is also desirable to utilize helicopters for the land-based survey­ ing of ice, having assigned to them a field crew dispatched to the region of the anticipated formation of a jam, where the helicopters can be used for moving the crew after the ice edge, and also for conducting the usual series of observations (of the ice cover's parameters, dimensions of floes, their diving beneath the ice cover's edge, etc.).

In the conduct of all forms of aerial ice surveying on rivers for coun­ teracting the ice jams, in the capacity of observers, it is necessary to use expert hydrologists from the local subdivisions of the Hydrometeorological Service*

The ice aerial surveying should be conducted in accordance with the instructions of the Hydrographic Administration of the Hydrometeorological Service [2T]•

Section 2* Using Planes for Explosive Work

The explosive tasks conducted on a river can be accomplished most pro­ ficiently with the utilization of helicopters*

In the conduct of preventive measures for combating jams (clearing considerable river sectors of an ice cover in order to create conditions for the unobstructed passage of ice), it is sometimes necessary to perform the blasting of the ice over a considerable river expanse simultaneously* It is possible to realize this with the employment of helicopters for delivering personnel, equipment and explosives to the points through which the route of

- 66 - explosions is to pass« The transportation of personnel and their transfer to new locations can also be done most conveniently with the aid of helicopters#

The most effective means of eliminating a jam is often to blast it with charges distributed at specific points in its body# The performance of such tasks is dangerous because the mass of the jam can be in a state of unstable equilibrium and the jam can breach at any time, particularly after the comple­ tion of blasts which at first glance do not seem to have produced results# In these instances, the helicopter may serve as the sole means of a repeated place­ ment of charges and the timely evacuation of personnel# Usually such a type of work is performed by a crew of 2-3 men landed at the head of the jam along with the drilling equipment and explosives# After the placement of charges, the crew of dynamiters is evacuated with a helicopter to a safe location# During the conduct of blasts along a jam, several crews can be set down simultaneously#

The points of placing the charges in the jam’s body can be determined by a visual appraisal# Such a type of observation, particularly during the forma­ tion of jams on large rivers, can be performed only with the aid of helicopters# Also, by circling around on a helicopter, we can evaluate the effectiveness of the blasts set off, if they have failed to break up the jam, and determine the locations for placing some new charges#

Section 3* Aerial Bombing

Bombing of ice jams from the air differs from other methods used to break up ice jams by virtue of the possibility of rapid organization and execution, associated with the mobility of aviation#

Bombing as a means for the destruction of a jam can be recommended uncondi­ tionally at the early stages of a jam’s formation# The work is organized ac­ cording to a system envisaging the continual surveying by aircraft of a river sector where formation of a jam is anticipated and the immediate calling out of the bombers as soon as the jam becomes perceptible# An. effect can be attained only in case of a jam’s formation during the daytime hours# Bombing during the early stage of a jam’s formation should not be conducted during the initial movements when an ice cover still exists downstream#

Bombing from the air for eliminating an already formed and compacted jam is not very effective; it should be applied in unique cases during catastrophic rises in the jam-caused level and the impossibility of adopting other measures within short periods# This is occasioned by the fact that at a relatively slight width of a river, particularly if (as often is the case) there are many populated points along its banks, the dropping of bombs of considerable weight from modern aircraft having high speeds is an extremely difficult problem and is dangerous in respect to the safety of the populated areas# On rivers of great width, bombing can be effective only with application of bombs of great weight, and in a large quantity, in order to affect a significant part of the jam simul­ taneously# Only in this case can a perceptible effect be achieved. At the same time, it is known that the heavier the bombs that are dropped, the greater the height from which this operation must be conducted, and the lower the accuracy#

- 67- An actual effect can be attained only in the event that the bombs strike the most stressed zones of the jam. Experience has shown that the use of a limited number of small bombs yields practically no results*

Utilizing bombing for destroying ice jams, we should be aware that it is by no means just any jam that can be disrupted with this technique. If the jam has formed in the tapering-out zone of the reservoir*s backwater curve in the presence of an ice cover in the actual reservoir, bombing can not yield any re­ sults because it will not effect the creation of conditions for the advancement and scattering of the ice masses*

The bombing of estuarial ice jams as a countermeasure is not very effec­ tive. For this type of jams, it is first necessary to free of ice the delta branches and to break up the fast shore ice; this will permit the receipt of ice which had accumulated in the jam.

On the origination of a channel-type jam at the edge of stable ice, it is first necessary to break up the stable ice at a sector located below the jam In this connection, it is necessary to perform the bombing while flying up­ stream, beginning from the location where the formation of a jam does not in­ flict great damage. After the completion of such a bombing, we can proceed to the blasting of the head part of the jam, if it has not become breached by this time *

In the formation of a channel-type ice jam on a broad river (in the ab­ sence of a stable ice edge), the lower sector of the jam’s body becomes compac­ ted and holds back the entire jam.

The elimination of this most compacted sector with the aid of bombing usually leads to the breaching of such a jam.

The order of tasks involved in destroying a jam by bombing is the same as in the destruction of a jam by blasting. We start to bomb a jam only after an ice-free water expanse has developed below the ice jam. The bombing is con­ centrated along one longitudinal line in order to create a channel. The path along which the bombs should fall is tied in with markers in the form of bar­ rels dropped from an airplane or by blackened strips* Bombing is not conducted over the jam*s entire area but is concentrated only with the limits of a course upstream from the jam’s lower edge.

The airplane enters the course from the lower part of the jam and drops the first bomb at roughly 50 m from the jam’s lower edge, while the others are released in succession at about the same interval. If ice movement fails to occur on the route subjected to bombing, the operation is repeated, shortening the spacing between the bombs dropped.

With the appearance of ice movement or ice passage, the bombing opera­ tions are halted and are then renewed in the indicated sequence after the ice has stopped moving.

- 68- Correction of the bombing is conducted by an observer located at a high point* The observer monitors the ice conditions in the vicinity of the jam and keeps a strict account of the jettisoned and exploded aerial bombs* The information is transmitted to the pilot by a mobile radio set* In the case of the formation of channel-type jams of great extent on fairly narrow rivers, where the bracing into the banks in each section is able to withstand high hydrodynamic loa-ds and the ice is not compacted, the utilization of bombing will yield practically no results* In certain cases, however, bombing conduc­ ted while flying downstream of the jam promotes the formation of a channel in the jam, along which water rushes from the above-jam pool into the lower one, favoring the erosion of the jam and a reduction in the jam—caused level*

If several successive jams have formed along the river's length, their elimination with the aid of bombing should be conducted beginning from the least risky jam, allowing for the degree of danger in each of the jams* When the upper jam is less dangerous, we should not accelerate its breaching; by re­ fraining from so doing, we do not intensify the jam located downstream*

Bombing can best be conducted during the hours of maximum solar radia­ tion, i.e* from 1200 to 1500 hours local time, since under the effect of ra­ diation, there occurs the thawing of the intercrystalline ice interbeddings and its strength is reduced. At a negative air temperature as a result of the freezing-together of the ice in the jam, the effect of an explosion will be appreciably less* In addition, it is desirable to coordinate the bombing with the time of the increase in water discharge; this will promote a reduc­ tion in the stability of the jam-type ice masses. The most complex problem in the use of bombing is the determination of the optimal size of bombs* It is known that owing to the plasticity of ice, explosions often punch holes in it of some given size, without disrupting the integrity of a number of floes located nearby. If moreover the bombing accur­ acy is poor, the bomb dropping will be of little use* The question of the effect of bomb explosions on the jam's body is de­ pendent on various conditions in the jam itself, and the design and weight of bombs still requires a lot more study. Available experience is very slight, uncoordinated and often not even recorded* We can consider hypothetically that for the elimination of a jam during its development, bombs of smaller size should be used* The use of small bombs for the elimination of a jam which has formed yields practically no results* In this case, it is necessary to use bombs weighing 250-500 kg* In solving the question of the bombs' sizes, it is necessary to weigh not only the shearing strengths of the jam, which depend on the nature of the channel and of the accumulated ice mass but also other factors such as the nearness of population centers, structures, and so forth* The destruction of an ice cover by bombing as a preliminary measure in combating ice jams should be forbidden. Owing to the ice's plasticity, the overall ice cover is weakly disrupted by the blasts; moreover, an increase in the size of charges yields a minor effect* Moreover, if the destruction is conducted on a large sector of a river, it will lead to nothing more than the killing of fish*

- 69- CHAPTER 7

PREVENTION AND DESTRUCTION OF ICE JAMS WITH EXPLOSIVES

Section 1. General Information

One of the methods of avoiding and counteracting ice jams is the appli­ cation of explosives. The appearance of powerful water-resistant explosives less dangerous to handle and also modern technology is expanding the possi­ bility of this method both in the period of preparing for the ice debacle and also during the liquidation of the ice jams which have formed. This is also favored by the low capital outlays and the simplicity of the means of mechan­ ization.

Explosive operations can be applied:

1) for the conduct of preventive measures assuring the jam-free passage of ice in a given river sector;

2) for the conduct of preventive measures in protecting bridges and hydraulic engineering structures during ice passage;

3) for operational counteracting of ice jams at the moment of their formation for the purpose of a rapid illumination of the causes (of large fields, their initial accumulations, etc.);

4) for the illumination of ice jams which have already formed; and

5) for counteracting the ice dams.

However, the apparent attractiveness of utilizing explosive techniques should not cover up the tremendous damage inflicted by explosions on the country's fisheries (particularly in recent years in connection with the overall reduction in fishery resources, and for an entire series of other reasons). Proceeding from this, the utilization of explosions for the op­ erations on preventing ice jams (the clearing of ice from considerable areas, the creation of open leads, channels and so forth) should be regarded as in­ feasible and should be forbidden by law.

Only in unusual cases should such activities be conducted at the de­ cision of higher authorities. Among these cases, we can include those when it can be foreseen that the possibility of the formation of an ice jam in a given year is high and can cause losses considerably exceeding those which would be inflicted on the fisheries.

In the present section, we clarify the questions associated with the application of explosions for the breakup of ice, elimination of ice jams and dams. In this context, the principal attention is paid to the specifics of

- 70 - such operations, taking into account that the general questions involved in the performance of demolition activities have been explained in many special standardizing documents and handbooks (we refer to the questions of drilling, characteristics of high explosives, technique of preparing the charges, pro­ viding the demolition crews with equipment, tools and so forth.

Section 2. Ice Jam Prevention With Explosives

In Chapter 1, we indicated that explosions are utilized in the conduct of preventive measures on counteracting ice jams, consisting in a timely freeing of considerable river sectors, of an ice cover, in the regions threatened by jams. In addition, the explosive operations are also applied for the development of conditions which would guarantee the integrity and security of bridges and hydraulic engineering structures and prevent the formation of ice jams in the ranges of these facilities. Since these pur­ poses are often pursued simultaneously, in the present chapter we will also review briefly the protection of structures against ice drift.

Organization of Preparatory Tasks in Protecting Structures Against Ice Drift

It is recommended that the explosive operations be started with the first indications of the thawing of snow and rise in water. In calculating the weight of charges for breaking the ice in the floodplain lakes and en­ closed basins, the specific consumption of high explosives (HE) is assumed to equal 0.5 kg/m^.

In certain instances, with a great thickness of ice cover, open leads are formed to protect the structures from ice passage. The sizes of the leads depend mainly on the width and thickness of ice cover, the length of its pushes, depth of the shore sectors of river, and the resistance of the structures to ice pressure.

Thus on medium-sized rivers, the length of a lead below a bridge should not be less than the width of the ice cover while the lead above the bridge should be twice as large. On small rivers, the total length of leads should equal 5-7 times the width of the ice cover. In special cases, the length of a lead above a bridge is extended to 500 m and more. The width of leads at the bridges on small rivers is assumed to equal the width of the ice cover.

Considering the awkwardness of the operations in flooding the ice in the absence of an open zone or lead, the open areas are usually formed by ejecting the ice onto the surface of the ice cover, utilizing large charges of explosives for this purpose. The maximal ejection of ice is achieved with a single-row arrangement of charges at a distance apart of 1.5-2.0 m of the depth of sinking the charge and a specific amount of HE equalling

- 71- 0.9-1.5 kg/nP. In this case, however, the width of the open area which is formed as a rule does not exceed 15 m. For the obtainment of wider open areas, we utilize a 2-3 tier arrangement of charges.

In the first case, the charges are arranged one opposite the other, while in the second case, the charges in the middle row are placed in stag­ gered sequence in relation to the charges in the outer rows. With a double­ row explosion of ice, use is made of underwater charges of the same weight. In the triple-row explosion of ice for obtaining a clearer open area, the weight of underwater charges in the middle row is adopted as 1.5-2 times greater than the weight of the charges in the outer rows. All the charges are exploded simultaneously.

In the formation of the narrower lanes and also in the creation of craters and the laying-out of individual floes, use is made of external and internal charges. The weights of external and internal charges depending on thickness of ice have been listed in Table 6.

The dimensions of floes after the cracking of the ice cover should as­ sure their free passage under the bridge spans. The ice cover near the hydraulic engineering structures is broken across the entire width of the basin.

Table 6

Thickness Weight of charges of ice ______(M l__ (m) Internal External

0,4 - 0.5 0.2 1.2 0.5 - 0.6 0.3 1.5 0.6 - 0.7 0.4 1.8 0.7 - 0.8 0.5 2.2 o © 00 • 0.6 2.6 0.9-1.0 0.8 3.2 1.0- 1.1 1.0 3.6 1.1 - 1.2 1.2 4.2 1.2 - 1.3 1.4 5.0

The area of an ice cover subject to cracking depends on the ice thick­ ness, nature of ice drift on the given river, reliability of the structure which is being protected, and so forth. The cracking of the ice cover serves as a preventive measure against the pressure of large ice fields against the hydraulic engineering structures and also for preventing the formation of ice jams.

- 72 - 4

The cracking of the ice cover is accomplished either by explosions of charges arranged in rows (by explosions in the compression area) or by the gradual breaking-off of individual floes. In these cases, the explosive operations are conducted in a direction opposite to the flow of water while in the absence of current, it is conducted on the leeward side.

For a reduction in the pressure exerted by the ice cover on poorly protected structures, in addition to breaking the ice around it, we utilize a softening ice cushion (protective belt of crushed ice) which, compacting g,t the time of pushes of the ice cover, absorbs a considerable amount of its pressure.

The ice cushion is formed by explosions of underwater charges located in a staggered sequence. The distance between the charges should be such that between the lanes, there would remain small ice arches which would be broken down during its shove.

Conduct of Explosive Operations For Crushing Ice To Avoid Ice Jams

For clearing large river sectors of ice, we perform demolition opera­ tions with the aid of the explosions of charges lowered under the ice. The explosions are conducted against the current usually in series in order that the broken-off chunks would drift freely downstream.

The weight of the underwater charge is determined with the equation:

Q - KW3 ,

where Q = weight of charge, kg; K = specific amount of HE, kg/m3 ; and W cal­ culated resistance line equalling the depth of sinking the charge into the water, m.

The specific consumption of HE varies from 0.3 to 1.5 kg/m3 and depends on the diameter of lane, necessary extent of disintegration of ice in the lane, and its spreading.

At K = 0.3 kg/m3 , a lane is not formed; with an explosion, we accom­ plish the cracking of floes into separate pieces. At K = 0.5 kg/m3, a lane is formed with a diameter 3.5 times greater than the depth of sinking the charge into the water. At K = 0.9 kg/m3 , a lane is formed with a diameter four times greater than the depth of submergence. In this case, the lane is cleared fairly well of broken ice. The lowest cost of operations is ob­ tained at explosion of charges at a depth of 1.5-3 m.

The depth W of sinking a charge increases with an increase in ice thickness.

- 73- The distance between charges is a function of the diameter of the lane which is being formed, the conditions of explosion and the nature of opera­ tion which is being conducted. The distance will usually vary from 5 to 15W.

During the cracking of ice (or the formation of a lane directly at an object) by explosions in the "pressure point", the distance between charges i s assumed to equal 5 W while in the presence of open areas or leads and the triggering of explosions without "pressure", the distance between charges can be increased to 15 W.

The weights of charges at varying thickness of ice and varying distance between them have been listed in Table 7.

Table 7

D istance* between Ice Depth of cha rges Weight of charge thickness lowering charge (ni) (kg) (m) (m) 5 w 15 w K * 0.5 k g /m3 K ^ 0.9 kg/m5

0.3 - 0.4 1.4 7.0 21 1.4 2.5 0.4 - 0.5 1.5 7.5 22.5 1.7 3.0 0.5 - 0.6 1.6 8.0 24 2.0 3.6 0.6 - 0.7 1.7 8.5 25.5 2.5 4.4 0.7 - 0.8 1.9 9.5 28.5 3.4 6.2 0.8 - 0.9 2.1 10.5 31.5 4.6 8.3 0.9- 1.0 2.3 11.5 34.5 6.1 10.9 1. 0 - 1.1 2.5 12.5 37.5 7.8 14.0 1.1 - 1.2 2.7 13.5 40.5 8.8 17.7 1.2 - 1.3 2.9 14.5 43.5 12.2 21.9 1.3 - 1.5 3.3 16.5 49.5 18.0 32.3

It is recommended that the underwater charges not be lowered under the ice through the cracks, current-eroded leads or between the junctions of floes since it is dangerous to approach them. In addition, there is a de­ crease in the area of ice cover broken by the explosions because the effect of explosion is propagated to a definite extent into the already broken ice cover. Most often, the charge is lowered beneath the ice on strong twine, one end of which is tied to the actual charge while the other is attached to a cross-beam laid athwart the hole. The charge can also be lowered on a pole. For this purpose, the charge is tied to the pole end; the second end of the pole is fastened to the cross-beam. On lowering the charge, in the neces­ sary cases, the spark-conducting cord is extruded onto the surface. At this time, the demolition cord is tied in several places to the twine or hole. The lowering of the charges on the safety fuse (cord) is forbidden.

- 74 - In addition to the conduct of explosive operations directed toward the complete clearing of a river sector of ice for the reception of ice arriving from upstream, for purposes of operational intervention in the ice jam forma­ tion process, it is desirable to perform the explosive operations in the most unfavorable locations (from the viewpoint of ice jam development) upstream. Among these locations, we include:

1) sector with a great ice thickness. The ice should be exploded at the shores (at points of support against the banks) and slightly below this sector;

2) sharp bend in the channel. The ice should be disrupted at the shores within the limits of the bend;

3) narrowing of channel. The ice should be blasted along the banks at the sector of narrowing and within the limits of the subsequent expansion,

4) sector with alternation of shallows and pools. The ice should be blasted at the shores in a pool sector below the shallows;

5) an island. The ice should be blown up at the shores and at the upper and lower ends of the island; and

6) a sandy spit. The ice should be demolished at the banks within the limits of the spit and also on the spit itself.

Section 3. Explosion of Large Ice Fields and Jams

As was indicated above, the struggle against ice jam formation by adopt­ ing preventive measures is much more effective than the destruction of jams which have already become formed. This also pertains to the technique of explosions*

Therefore it is preferable not to permit ice jams, eliminating them at the time of formation. For this purpose, we organize special mobile groups which blow up the large fields, the initial ice accumulations and so forth.

The ice fields are cracked by an explosion both of underwater and of external charges. At the outset of ice passage when the ice is moving in a solid mass, it is not possible to approach the large floes. In this in­ stance, they are cracked by explosions of charges thrown from shore from a shelter, from small light suspension bridges built on steel cables between narrow banks and from helicopters. For protecting the demolition workers from the impact of ice fragments, permanent shelters are built at the points of throwing the charges.

- 75- The rate of a charge which is being thrown should not exceed 2 kg. When the ice drift is not continuous, an ice floe can be broken by the ex­ plosion of an underwater charge with great effect and less danger to the demolition workers. At this time, it is recommended that the charges be tossed into the water ahead of the floe in order that the explosion would occur after the drifting of the central part of the floe over the charge. If one is able to approach the floe on a boat, or (if possible) to walk over the ice with the utilization of boards or strong narrow wooden ladders, the floe could be exploded by a charge lowered under the water. At this time, the working of one demolition worker on weak ice is not permitted. In this instance, another demolition worker should be located at a distance of 3-4 m and should have a life-saving equipment ready. During the cracking of drift ing floes (also during the elimination of ice jams), the demolition expert is allowed to explode only one charge at a time.

The typical weights of underwater charges for the cracking of average thickness floes (with a thickness of around 60 cm) have been presented in Table 8. Table 8

Transverse size 10-15 15-20 20-30 30-40 40-50 50-70 of floe (m)

Charge weight (kg) 0.5 1 2 4 6 12

For cracking ice measuring more than 70-80 m with an explosion, the weight of the underwater charges should not be less than 15-20 kg. The cracking of floes by blasts of several underwater charges is permitted if these floes are adequately strong.

In the cracking of floes by external charges, the safe distances be tween them have been indicated in Table 9. Table 9

Weight of external 0.5-0.7 0.7-1.0 1.0-2.0 2.0-3.0 3-5 5-7 7-10 charge (kg)

Distance between 3 4 6 7 9 11 13 charges (m)

- 76 - The recommended weights of external charges depending on thickness of crystalline ice have been listed in Table 10. Table 10

Ice thickness (m) 0.2-0.3 0.3-0.4 0.4-0.5 0.5-0.6 0.6-0.7

Weight of external 1.2 1.6 2.0 2.4 3.0 charge (kg)

Ice thickness (m) 0.7-0.8 0.8-0.9 0.9-1.0 1.0-1.2 1.2-1.5

Weight of external 3.7 4.5 5.0 7.0 10.0 charge (kg)

During the blasting of ice jams, we should remember that the breakup of the jam can be sudden; therefore it is necessary to be alert for the shov­ ing of ice and to move across it while observing all the safety precautions.

The charges are placed in locations where the water flow and wind favor the transport of broken ice. The ice jam is eliminated by gradually fractur­ ing it in a direction opposite to the water current.

The success of the operation depends on the proper determination of the location for the charges, i.e. in the most compacted leading part of the jam.

In the elimination of ice jams, for determining the typical weight of charges, we can utilize the data tabulated in Table 11.

Quite often on relatively shallow rivers, the ice accumulates to 3-4 m above the water level and in certain places reaches the bottom. Such ice jams are eliminated by the conduct of successive explosions of powerful charges of HE (20-30 kg), located across the center of ice jam, along the river flow. In the case of stability of the jam, the subsequent charges are placed at the location of those which have been exploded, with a preliminary clearing of the broken ice.

For accelerating the activities on eliminating a heavy ice jam, use is made of charges weighing at least 30-40 kg which are lowered in the water be tween the floes on a rope with a loop.

- 77- Weight of charge (kg) At explosion At large-scale explo­ of single charges or during Depth of sinking sions and distance large-scale explosion and charge in water between charges : distance between charges (m) (5 W) (10 W)

t . 0 -5.0 3 15 1 .5 -2 .0 8 4 0

2 .0 -2 .5 15 80

2 .5 -3 .0 25 130

3 .0 -3 .5 4 0 20 0 3 .5 -4 .0 6 0 300 In the presence of floating logs which have become frozen into the ice, one should increase the weight of charges slightly or decrease the distance between them. For the simultaneous explosion of several charges, use is made of an instantaneous detonating fuse. It is forbidden to lower the charges on the detonating fuse without supporting attachments.

Certain techniques of blasting the ice jams have been explained below.

Narrow Rivers (width of river up to 200 m)

If in a river sector being protected, an ice jam has begun to form by means of the piling up of floes or the hummocking of ice at the edge of a stationary ice cover, one should demolish the ice cover. An ice cover should be destroyed from below upstream, commencing from the location where the formation of the jam is not inflicting damage.

If the ice jam has already formed and is remaining in place even though the ice cover downstream of the ice jam has been eliminated, one should blow up the ice in the sector of the leading part of the jam at several points along the shore (at the point of ice thrust) or even along the navigable channel of the river.

In case of the formation of a jam by pressure on the shores, one should blow up the ice fields or ice at the lower edge of the jam and, if the jam still remains, one should set off a series of blasts along the jam. Ohe should dynamite the ice along the length of the jam having formed on a narrow river, from above downstream, or simultaneously along the length of the jam. This promotes the formation, in the jam, of a channel along which water strives from the upper pond into the lower reaches of the jam. In this case, the jammed water level gradually subsides and the jam is washed out.

In case of a great extent of a jam (more than 15-20 km) on a narrow river, the blasting of ice in a jam (as already noted) is not very effective. In certain instances, however, the ice blasts conducted simultaneously along the jam's length (or from above downstream) can be of benefit.

Wide Rivers (Width Greater than 200 m)

At formation of an ice jam owing to the ice diving under or hummocking at a stationary ice edge in a protected sector of a broad river, one should blow up the ice cover below the jam. The ice cover should be blasted in the same sequence as on a narrow river.

Should the jam remain in place (after the elimination of the ice cover below the jam) and become compacted, one should set off a series of explosions along shore (at ice pressure points) or in the middle of the river within the limits of the lower most consolidated part of the jam. It is desirable to conduct the blasts simultaneously.

- 79- We should point out that if the jam had already formed, in many cases there is no requirement to blow up the ice cover ahead of the jam, particu­ larly if it does not comprise the cause for the jam's formation. A success­ ful blasting of the lower most compacted part of the jam usually leads to the breakup of the jam. The hummocky accumulations of floes, moving down­ stream, break up the ice cover within the limits of a uniform (in respect to channel morphology) river sector. At the obstacles which can serve as a cause for jam formation, such an accumulation of floes usually stops and the jam is re-formed.

The ice blastings should be performed during the hours of maximum solar radiation, i.e. from 1200 to 1500 hours local time since at a positive temperature under the effect of radiation, thawing of the intercrystalline ice interbeddings takes place.

Section 4. Explosive Destruction of Ice Jams

During the initial period of ice jams' formation, the points where the risk of their formation develops are jolted by blasts of explosives thrown from shore, boats, icecutters etc. Such explosions provide the uninterrupted passage of intra-water ice which is often restrained at the shores. It is necessary to survey these places periodically for eliminating the fast shore ice and causing the passage of the remaining intra-water ice.

In winter the ice jams become formed more often under an ice cover and one can eliminate them at the time of formation by explosions of under-ice charges lowered through the surface ice cover. The charges should be set in longitudinal rows in such a way that as a result, passage for water along the entire length of jam would become formed.

It is necessary to destroy the jams on a timely basis, since they are difficult to break up after they have formed. We are aware of cases of us­ ing up to 10 tons and more of high explosives on blasting one jam, while certain jams in effect do not yield to the effect of explosives.

Section 5. Using Helicopters for Explosive Work

Currently in the conduct of explosive operations, successful use is being made of helicopters which are utilized both for delivering the teams and HE (high explosives) and for directly destroying the jams.

The demolition operations with the aid of the MI-4 helicopters are conducted with the emergence of demolition workers from the helicopter onto the ice, and directly from on board the helicopter. During the activity of workers engaged in breaking up the ice, the helicopter hovers overhead.

Under the first method (with emergence of demolition workers), the placement and explosion both of single and of tandem charges is possible.

- 80 - 4

In this case, the demolition expert walks on the ice, places the charge or lowers it beneath the ice, returns to the helicopter, lights the fuse cord and tosses it onto the ice; thereupon, the helicopter moves on to the next charge. At this time, the length of the first fuse cord is chosen so that its burning time would provide the chance for the placement and ignition of several charges and the removal of the helicopter to a safe distance.

The burning time of the first fuse is controlled on the basis of a stopwatch and a control fuse.

During the operation, the demolition worker and the flight mechanic don life jackets and are linked by safety belts to the helicopter. The dynamiter located on the ice is fastened to the side of the helicopter by a line 10-15 m in length. The door to the helicopter cabin has first been re­ moved on the ground. The flight mechanic monitors the actions of the dyna­ miter and maintains contact via aircraft intercom with the helicopter com­ mander.

In the second case after the helicopter has hovered over the jam, the dynamiter (when ordered) lowers the charge with the attached detonating fuse on a rope onto the ice or water between the floes. Having placed the charge, the dynamiter connects an ignition primer to the end of the detonating fuse, lights the primer and lowers it onto the ice. In all cases, at least 2 demoli tion workers should be on board the helicopter; one of them acts as the leader.

The helicopter should be equipped with a hoisting winch and a safety ladder; in addition, it should contain safety belts, life jackets and a first aid kit.

During operations with the helicopter, we should recall that an in­ crease in the weight of the charge leads to an increase in the hazardous zone iri respect to the effect of the air shock wave for the helicopter, sig­ nifying also an increase in the length of the fuse.

The critical length of the fuse is 10 m; this corresponds to 15 minutes of burning. Taking into account that during this time, the dynamiter has to ignite several charges and then the helicopter has to move off for a maximal distance, the weight of the charges exploded simultaneously should be limited to the weight of HE carried by one dynamiter.

The determination of the distance safe in respect to effect of air wave is conducted according to the formula:

rB = 150 Vo",

where rg = safe distance, m; and Q = weight of HE charge in kg.

- 81- The dimensions of the zone safe in regard to effect of the shock wave on a man are established according to the equation:

rmin - 15

This formula is utilized only when according to the operating condi­ tions, it is necessary to bring the dynamiter as close as possible to the work location; under normal conditions, the result obtained with the for­ mula should be increased by 2-3 times.

The tasks are performed in strict accordance with "Technical Rules for Conducting Demolition Tasks" and "Standard Safety Rules in Performing Demoli­ tion Work".

The main advantage in conducting explosive tasks with the aid of a helicopter as compared with other techniques consists in the possibility of placing the charges at practically any point in the jam. As compared with bombing, this procedure is distinguished by considerably greater accuracy of placing the charges and hence by a greater effectiveness of the demoli­ tion operations.

- 82- CHAPTER 8

UNOBSTRUCTED PASSAGE OF ICE THROUGH HYDRAULIC STRUCTURES DURING CONSTRUCTION AND USE OF HYDROELECTRIC STATIONS WITHOUT ICE JAM FORMATION

The construction of hydroengineering complexes on rivers alters their natural regime» Moreover, depending on the system used for accomplishing the tasks, conditions can develop favoring the formation of ice jams» Such jams in the region of building a hydroengineering complex can lead to the flooding of the basins and of incomplete structures; therefore measiires should be en­ visaged to prevent such an occurrence.

Experience gained in building hydroengineering complexes on rivers with severe ice conditions indicates that the unobstructed passage of ice can be achieved with the observance of the necessary measures of a procedural and engineering nature« The present chapter has been written on the basis of gen­ eralizing this experience. We consider simultaneously in it the questions of ice passage through finished structures, since their composition can also in­ clude the same ice—passing elements as during the period of erection.

Section 1. General Conditions for Passage of Ice Through Structures

The planning of hydroengineering complexes on rivers where a persistent ice cover forms during the winter should be conducted with consideration of the passage or confinement of ice in front of the structures in the construc­ tion and operational periods.

Under the necessity of the passage of ice via incompleted or operating structures, they should have ice-dumping openings assuring the unobstructed passing of ice.

The selection of the type and overall dimensions of the ice—dumping structures should be accomplished with consideration of the adopted design of hydroengineering complex, the systems for its erection based on studying the river's ice conditions, utilization of the experience gained in using the structures existing under similar conditions, and the recommendations given in the present chapter*

- 83- We can consider as ice-passing conduits the open spans, bottom openings, shore trench-type spillways, narrowed sectors of channels, tunnels etc#

The line in the hydroengineering complex, through the structures of which we postulate providing the passage of ice during the construction or op­ erational periods, should desirably be chosen in such a way that above and be­ low the structures, there would be a long straight river sector without is­ lands, removed from the locations of ice jam formation# In case of the presence of rapids in the region of the proposed construction of the hydroengineering complex, the complex's line could feasibly be planned beyond the rapids# This greatly facilitates the conditions involved in ice passage via the structures during the construction period, since ice which has been fragmented in the ra­ pids will approach the structures#

Just beyond the hydroengineering complex, it is not desirable to build bridge crossings with spans of slight width, or any embankments in the channel or along the banks, leading to a narrowing of the channel# Otherwise it will be necessary to undertake measures for the unobstructed passage of ice in the lower (tail) reaches as well#

In the event that the hydraulic development is located in a cascade, one should envisage the possibility of tripping the water levels in the down­ stream hydraulic development, which would assure the transport of ice beyond th,e structures# At the upstream hydraulic development, it is advantageous to reduce the discharges of water during the spring, which would permit a certain additional delay in the river's opening in front of the hydraulic development under protection and would lead to a reduction in the thickness and strength of the ice in this sector; this means that it would also lead to the provision of more favorable conditions for the passage of ice#

In grouping the hydraulic development's structures, we should have the following concepts in mind:

-rthe ice—passing bays should be located within the limits of the river's deep channel; - at placement of the hydraulic development on the bend of a river, it is desirable to locate the ice-passing bays at the concave bank toward which the main ice mass is usually directed; and - within the limits of the ice-passing front, one should not place spans or openings with a markedly different passing capacity since this would lead to an irregular arrival of ice at the structure and could cause prolonged stop­ pages of ice floes in front of the openings or spans with a lesser passing capacity#

In the stage of the working drawings, the arrangement of the ice-dump­ ing openings should be confirmed by hydraulic investigations of the hydraulic development on three-dimensional models#

- 84- During the admission of ice vie, the uncompleted and operating structures, in the tail waters, there should be assured a surface regime of interlinking in order to avoid the ice's destruction of the channel reinforcement beyond the structures. If for the development of a surface interlinking regime in the tail water, a lip is mounted in the spillway, a preliminary verification under lab­ oratory conditions will be necessary to check its security during the passage of ice. In case of the destruction of the lip, we must abandon its installa­ tion and provide the required reinforcement of the river channel beyond the structure•

The ice—passing openings of the structures in the construction period and also in the operational period when the releases of water during ice pas­ sage are unlimited can be closed by sluice gates of varying design; during the passage of ice, these gates should be open for the total height* For the ice- dumping openings with limited releases of water, in all periods we recommend the application of drop gates or lifting gates with drop valves. Maneuvering the sluice gates to the ice-passing holes during ice passage should be avoided. If it is impossible to completely exclude the maneuvering, it is necessary to develop a set of procedures to assure the accident-free operation of the sluice gates (strengthening of the gates with allowance for a possible ice load, decrease in thickness, strength, speed and dimensions of the ice fields approach­ ing the spans)•

The depth of flow ahead of the structures, within their limits and be­ yond them should assure the unobstructed passage of ice and protect the var­ ious design elements of the structure along the ice-conveying conduit against destruction by ice. The elevation of the base to the various trestles, bridges, temporary structures built above the ice—dumping spans should be allocated with consideration of the possible approach of ice accumulations to the spans, and the ice’s twisting within the limits of the spans, but not less than 3 - 5 m (depending on the force of ice passage).

The engineering measures adopted for providing the conditions of ice movement via the structures should be oriented toward the longest possible de­ laying of ice in the upstream water, leading to a reduction in ice thickness and strength and to a decrease in xts total volume; these measures should also be directed toward an earlier opening of the river in the downstream water as compared with the upstream water.

In reviewing the questions of ice passage via the structures, the fol­ lowing aspects are given:

a) type and configuration of ice-bearing structures are assigned with consideration of the adopted design for the hydraulic development; b) the hydraulic conditions within limits of the ice-conveying chan­ nel (levels and configuration of water surface, depths of flow and pressure above the spillways' crest, flow conditions in the downstream water, etc) are established based on the rated and laboratory data;

- 85- c) characteristics of ice motion (thickness, speed and dimensions of approaching ice fields or accumulations of jam-type ice, intensity of ice’s arrival and proposed volume of discharging the ice) are predicted on the basis of a preliminary study of the conditions involved in a river’s opening for a number of years; and d) the forecasting parameters of ice are assigned on the basis of pre­ liminary studies in the region under consideration* Should such studies be lacking, we assume roughly that

R - R ^ - 45 tons/m2, u c JC 7 where R , R ^ = provisional resistances of ice to bending and compression* u* c jl

Section 2* Plan for Ice Passage During the Erection of Hydraulic Structures on Rivers with a Heavy Ice Flow

In the erection of hydraulic structures with low (height less than 25 m) concrete dams, the passage of ice can be achieved through narrowed channels, bottom outlets (lower ramp) or with a high ramp (ramp elevated above the river bottom)• In the operational period in the hydraulic structures with low con­ crete dams, one can achieve a partial or complete confinement of the ice (de­ pending on the dimensions of the reservoir and the current speeds in the up­ stream water)*

During the erection of hydraulic structures with average (25-75 m) and high (more than 75 m) concrete dams on large rivers, the passage of ice can be accomplished via narrowed channels, crests with low or high ramp, bottom out­ lets with a ramp at the level of the river bottom or with a ramp elevated above the river bottom* In the operational period at the hydraulic structures with medium-high and high concrete dams, ice passage is not envisaged, since the large reservers which are created ahead of such hydraulic structures permit the ice to be confined entirely in the upstream water*

In the erection of hydraulic structures with rock-filled dams, the ice passage can be achieved via a narrowed channel or a flooded incomplete rock fill, and later on through shore trench-type spillways or tunnels* In the oper­ ational period at the hydraulic structures with rock-fill dams, we can achieve a partial or complete confinement of ice, depending on the reservoir’s dimen­ sions and the current velocities in the upstream water*

In the development of systems for ice passage, it is necessary to take into account the design of the hydraulic structure, the system of its erection and the features of the river’s opening* In this connection, we should strive toward the goal that the ice-discharging structures would provide the condi­ tions under which it is possible to confine the ice for a certain period, which leads to a decrease in its thickness and strength or to the formation (at the approach to the ice spillways) of increased gradients of the water surface, under the effect of which the breaking of the approaching ice fields into sep­ arate floes takes place*

- 86- Section 3# Passage of Ice Through Narrowed Channels

For narrowed river channels, in addition to the general concepts, a con- sideration of the ice passage conditions reduces to the stipulation of:

a) width of narrowing; b) depth in the narrowing part; c) height of arches demarcating the incomplete structures; and d) optimal profile and configuration of bridges and measures to safe­ guard them against damage from ice#

The width of narrowed channels, proceeding from the condition of ice pas­ sage,should be assigned on the basis of studying the river's ice regime, with utilization of the experience gained in operating the structures existing under similar conditions and is assumed to be not less than 30$ of the width of the river occupied by drifting ice under usual conditions#

The depth of flow along the navigable channel of the narrowed part must provide the passage of clumps of jam-type ice and for large rivers with heavy ice movements, it should be not less than 5-6 m#

With water surface gradients greater than 0#007, at the entrance to the narrowed channels, ice fields with 50 m dimensions and larger lengthwise of the flow are broken into separate ice strips# The length d of ice strips sep­ arating from the ice fields at hydraulic drops on entry into the narrowed chan­ nels can be determined based on the equation:

d = 4*4 V h R u , where d = dimension of ice strips in direction along flow, for strips separating from ice fields in hydraulic drop; and h = ice thickness.

During movement within the limits of the narrowed part, the ice strips break into individual floes; their sizes do not exceed 2d.

The height of the arches bounding the incomplete structures, on ice pas­ sage via the narrowed channel, should be verified for the case of a possible rise in levels in the upstream and downstream water owing to a breaching of ice jams in the upstream river sectors or due to the formation of jams beyond the narrowed part.

In the narrowed part formed by the trench arches in the first stage, the upper abutment haunch, upper and longitudinal arches are exposed to the great­ est effect of the ice*

In selecting the profile and material for the upper cofferdam, one should have in mind that the cofferdam is subjected to the intensive dynamic effect of the ice only during the initial movements« Subsequently, owing to the features of hydraulics, a unique ice buffer forms ahead of the cofferdam,

- 87- protecting it from the dynamic effect of the ice fields* The cofferdam should withstand the static pressure from the ice heaps; their height on rivers with heavy ice passages can reach 10—15 m*

If the length of the longitudinal cofferdam does not exceed the width of narrowing, its protection against the dynamic effect of ice can be provided by a slight advancement of the upper haunch toward the narrowing part* In the case of long longitudinal cofferdams, it is necessary to install short grous­ ers from the longitudinal cofferdam toward the narrowed part in order to pro­ vide stalled flow-around of the cofferdam by the current and ice* The river declivity of the longitudinal cofferdam made of earth should be reinforced with a riprap (rock cover). The profile of short grousers run from the longi­ tudinal cofferdam toward the narrowed part should be fairly bulky (not less than 10 m along the top) in order to withstand the effect of the ice*

The design of the upper abutment haunch extended toward the narrowed part should be reckoned for the absorption of ice loads from static pressure during accumulation of ice and from dynamic pressure during ice pushes and passages•

For the crib cofferdams, the upper haunch should be closed on the river side by a riprap not less than 10 m wide at the top* The coarseness of the main mass of riprap on the upper abutment haunch should not be less than 0*3- 1*0 m for rivers with severe ice conditions*

Remark. The ice loads are determined in conformity with SN 76-66*

Section 4* Passage of Ice Over Spillways of Concrete Dams

The consideration of the conditions of ice passage via the spillways of concrete dams reduces to the stipulation of:

a) width of individual ice-discharging spans; b) total width of ice-discharging front; c) ratios of widths of individual piers and spans, at which passage of ice is not made difficult; d) forms of haunches in individual piers; e) marginal advancement of individual piers toward upstream water; f) adequate depths in spans; and g) type of protection of spillway elements against destruction by ice*

For the spillways with a low ramp, in presence of a hydraulic drop as­ suring the breaking of ice fields into separate strips, width of the individual ice-discharging spans should not be less than 0*75 d*

- 88- This concept is valid at 2*5 m/sec< ^ 6.0 m/sec and at average dimensions of floes (approaching the spans) ranging from d to 1.5 d (V/\ = ap­ proach speed of floes toward the spillway spans).

For the spillways with a low or high ramp, at the approach to which hydraulic drops and water surface recession curves are lacking, the minimally required width of individual ice-discharging spans can be established on the basis of the following approximate relationships:

iv = 1*5/9/^ at 2*5 m/sec > ^/i^l«5 m/sec;

^ i? = 2.0B t at 1*5 m/sec > ^ >0.7 m/sec; and W = 2 . A 1 at 0.7 m/sec > m/sec« Given the impossibility of installing spans with a width determined on the basis of these dependences, it is necessary to develop a set of proced­ ures oriented toward reducing the thickness and strength of the main mass of ice which is being passed; this permits us to provide the ice passage via spans with a smaller width.

For the spillways with a high ramp, at the approach to which the ice fields (commensurate with the overall width of the ice—discharging front) do not break up at the hydraulic drops but can break up on the water surface recession curves directly in front of the individual piers, width of the ice- discharging spans should be determined with allowance for the breaking of the ice fields on the recession curves.

The dimension of ice strips C in a direction along the flow which (strips) are separating from the ice fields on the water surface recession curves, can be determined with the equation:

while width 1 of the individual ice-discharging spans should not be less than 1.2 C.

The separate piers of the spillways should be designed with a vertical upper face and with a tapered haunch. Over the span's length, the piers must have a constant thickness and must not have any sections that become flooded during the ice passage* If owing to design, engineering or any other reasons, the thickness of the piers is assumed to equal 6-10 m, at the intake to the spans, they can have a variable thickness, decreasing toward the abutment haunch.

Thicknesses of individual piers in the spillways of concrete dams should not be greater than 0.6 of the ice-discharging spans' width. At greater thickness, there is an increase in the piers' resistance to the advancement of ice into the spans, while for the spillways with a high ramp, breaking of the ice fields on the recession curves in front of entry to the span becomes dif­ ficult.

- 89- For assuring the breakup of the ice fields on the recession curves of the water surface ahead of the spillways, similar in configuration to the spillways of a practical profile, the advancement of individual piers from the upper face of the spillway toward the upstream water should be less than 1*5 H (where H = amount of pressure above the spillway crest)•

The total width of the spillway front should be allocated on the basis of studying the ice regime of a river, with utilization of experience gained from the operation of structures existing under analogous conditions*

Whenever the river has the width 1 0 0 0 m > B ,> 150 m, width of the ice­ discharging front is determined according to the equation

b S/ b = o.oi S a, , where = total width of structures’ ice—discharging front; and 0^ = min­ imally required width of individual ice-passing span (depending on system for passing the ice, the 0A -value can be assumed to equal o r $ A ^ , - respectively) .

Flow depth in the ice-passing spans of spillways with a low ramp should not be less than 4-5 m. For spillways with a low ramp and during the approach of ice (in the form of ice fields) to them, which (ice) could break up on the recession curves ahead of the spans, the minimal amount of pressure head as­ suring the unobstructed passage of the ice can be determined with the formula: H . = h + 0*2 C m m where = minimal amount of pressure head above spillway crest, guarantee­ ing the unblocked passage of ice; and h = ice thickness.

Section 5* Passage of Ice Through Bottom Outlets

For the bottom outlets, the consideration of the ice passage conditions reduces to the establishment of the critical flooding of the ceiling in the bottom outlets, proceeding from the condition of the ice not diving under, and the determination of the periods of the ice’s confinement ahead of the structures. For the bottom outlets of concrete dams with height ranging from 5-15 m, functioning during the construction period as a complete section without vortex funnels at the intake, the amount of their ceiling’s flooding, at which the ice’s diving under ceases, can be determined from the following simplified relationships:

Hk ^ . s VT (single outlets), and Hg. = 5.0 (paired outlets), where a = height of bottom outlet in the intake sector.

- 90- In the presence of intensive vortex funnels in front of the entry to the bottom outlets, the H^-value should be increased 1*5 times#

During the passage of ice through the bottom outlets in rivers with heavy ice movements, the flooding of their ceiling should not exceed the height of the openings#

For concrete gravity (solid) dams, width of the bottom outlets through which it is necessary to accomplish ice passage, based on conditions of the dam’s strength must not exceed:

a) for dams with height of over 70 m, 50% of the distance between the through expansion joints of the dam; and b) for dams with height up to 70 m, 6C/fo of the distance between the dam’s through expansion joints#

For providing the unobstructed passage of ice via the bottom outlets of concrete gravity dams, the width of which (based on conditions of the strength of individual dam sections, depending on height of dam and construction region) can not exceed 5-15 m, it is necessary to achieve the temporary confinement of the ice in front of the structures in order to reduce its thickness and strength#

The periods of temporary confinement of passing ice ahead of incomplete structures with bottom outlets designed for ice passage should be established on the basis of the predicted influx of water, development of ice conditions in the water-races, pattern of thawing and decrease in ice strength, thé stor­ age capacity in front of the structures and with consideration of the work ex­ perience acquired at structures occurring under similar conditions# For rivers with heavy ice passages, this period should not be less than 5-7 days from the day of opening the river in the lower water-race*

In case of the need to pass the ice through the tunnels and shore trench spillways, one should consider the general concepts on ice passage and the ex­ perience gained in operating structures under analogous conditions# As models for approximate calculations of ice passage, for tunnels we can assume bottom outlets of the same section, while for the shore spillways, we can adopt spans of spillways with a low or high ramp.

Section 6# Slowing the Ice Flow in Front of Structures

Ice passage through structures during the building and operational per­ iods should be envisaged only when the flow velocities in the upstream water reach values capable of causing a thrust to the ice fields separated from the banks#

For a rectilinear configuration of shores, ahead of the hydraulic de­ velopment in a sector with length up to 15B, the average flow speeds *\f which ice motion toward the structures is possible should be higher than the values determined with the equation: [see next page]

- 91 - ,nr = 4.25 -/bR /B. v av y u The decrease in the ice’s shearing strength limit is determined experimentally (or by analogy with other rivers)»

In case of a meandering shore configuration in front of a hydraulic de­ velopment, the *\f -value needs to be increased by 30$ av For the temporary confinement of the ice passage ahead of structures, one should proceed to raising the levels in the upstream water (for creating slower velocities) after the separation of the ice cover from the shores*

In case of the impossibility of providing the complete delaying of ice ahead of the hydraulic structures during their operation, it is necessary to provide in its composition some ice-passing spans or outlets, in the planning of which it is necessary to take into account the general concepts pertaining to the passage of ice*

For the hydraulic structures with surface spillways closed by lifting sluice gates, in case of failure to pass ice, the minimally necessary amount of their opening based on conditions of protection against the floes’ diving under the gates is about equally to 0*2 of the total opening of the outlet*

In numerous cases for the confinement of ice in waterways, in front of structures and in the intakes to all possible types of water-transferring out­ lets, we utilize floating booms* In determining the conditions of ice’s diving beneath a boom, we can recommend utilizing the following experimentally estab­ lished relationship: 0 T c r = y ' ° ‘ °35gj£, where A = length of floe; and ' i f = critical velocity, starting from which the diving of a floe having a given length will take place.

- 92- CHAPTER 9

HYDRAULIC AND THERMAL REGULATION OF WATER BODIES AND CURRENTS TO PREVENT AND COMBAT ICE JAMS

Section 1. Ice Jam Formation

The formation of jams leads to a decrease in the throughput capacity of the channel and to a rise in water level above the jam; this can cause the flooding of the surrounding locality and a reduction in the level below the jam. The formation of slush ice in the channel of the river and reser­ voir is the cause for the serious ice complications in the water basins (freezing around pipes, debris-collecting screens, plugging of caps) which can often lead to a total stoppage of water supply.

The ice dams are typical for rivers with a considerable current speed. Ice dams occur during the freezing period and in the winter season. In most instances on the unregulated rivers, ice dams reach dangerous proportions in early winter. In the lower pools of the HES and on many mountain rivers, the maximal winter (dam-related) level can occur at any time.

The process of ice dam formation is determined by a combination of factors which can be divided into two groups:

1. Factors favoring the formation of slush.

2. Factors favoring the stoppage and freezing over of slushy masses.

The factors in the first group are determined by the velocity regime of flow and by the climatic (temperature) conditions in the region. At a certain combination of current speed (usually exceeding 1 m/sec) and air temperature, there occurs a supercooling of water, leading to an intensive formation of bottom ice and slush.

The factors in the second group are determined by the morphometric features of the river sector creating conditions for the confinement and freezing together of slush (bends in the channel, breaks in the general longitudinal profile, islands and shoals).

In this manner, the ice dams are mainly formed in the same places as the jams, provided that upstream, there occur the processes of intensive formation of large masses of slush. This does not exclude the fact that there are sectors where the location of dams' formation varies from year to year. In this way, the conditions involved in the formation and develop­ ment of ice dams are:

a) the presence of a nonfreezing river sector (shoals, sectors with increased current speeds, open leads and so forth) or of an open water sur­ face of the reservoir;

- 93- b) the presence of negative air temperature below the critical point, causing heat exchange from the water surface;

c) the presence of turbulent flow in the current and of intensive wind- caused wave action on a reservoir, favoring the supercooling of the water mass and the crystallization of the intrawater ice;

d) increased intensity of slush in the flow as a whole;

e) presence of special orographic features in the river channel, favor­ ing the entrapment of the ice mass (meanders, bifurcation and the like) and also various obstacles, including hydraulic engineering structures, islands and so forth; and

f) variation in current speeds on the river (pools-sandbanks, points of tapering out of backwater curves of the reservoirs, and so on).

Velocity conditions in a river influencing the dam formation can be sub divided in the following manner:

a) at 2/= 0.4-0.5 m/sec and less, the freezing of a river occurs on formation of the ice cover. If the slush has already formed upstream at velocities 7/ >0.5 m/sec, having entered the zone of velocities 7^4 = 0-5 m/sec, the slush floats up and will move in the form of a slushy cover. At negative temperatures, the slushy cover quickly freezes over;

b) at = 0.7-0.067 H m/sec, where H = depth of flow, m, the slushy cover will not sink;

c) at If = 1.5 m/sec, the slush begins to propagate over the entire section, partially covering the stream flow surface also; and

d) at 1/> 1.5 m/sec, there occurs the complete suspension of the slush. The water surface becomes denuded.

The permanence of the frontal edge of the ice cover also depends on the stream flow velocity conditions. At a velocity value higher than the critical, the ice edge will not be stable. Part of the slush will move away under the ice cover and will serve as material for the formation of the ice dam.

Under actual conditions, the pattern of the phenomenon is complicated by constant fluctuations in hydrometeorological elements. Thus in case of heavy frosts, much ice forms on the river, particularly if the length of the slush-forming (i.e. nonfreezing) sector is considerable. This ice has considerable strength and owing to low air temperature, freezes together readily; the edge advances rapidly, the slush-related rise in level proves

- 94- slight. On the other hand, in the case of slight freezings, thin unstable small floes and slush float up to the edge; their freezing together occurs slowly and from time to time, hummocking does occur. As a result, the edge advances gradually with an appreciable rise in level.

In the downstream waters of the HES, the process develops in a similar manner. The difference is that through time, the movement of the edge slows down (owing to a decrease in the length of the ice-forming sector) and then ceases completely. The size of the open lead during stable position of the edge is determined by many factors, i.e. heat losses, water flow rate, water temperature and so on.

To date, the methods of forecasting the ice dams just as the ice jams have been developed very poorly. Predictions are possible only in isolated cases, given a more or less constant location for the formation of the ice dam.

The prediction of the maximal dam-related level is accomplished on the basis of tying it in with the water content in the pre-freezeup period, e.g. with the average water discharge during November. Such relationships have been obtained for the Angara, Neva and Svir* Rivers (timeliness of forecasts is 1.0-1.5 months). On the rivers where the water discharge in pre-freezeup period is subject to considerable fluctuations, we con­ struct a relationship of the maximal dam-related level with the discharge during the freezing period. The timeliness of the forecast in this con­ nection is reduced to 3-5 days.

The thickness of the ice dam forming in the low end of the nonfreezing sector of the river is in direct relationship to the ice volume. Accordingly for purposes of forecasting, we can establish a connection between the maxi­ mal dam-caused level with the ice runoff.

A quantitative estimation and prediction of the pattern of the level during the ice dams are not yet possible. Only on the basis of many years experience do we generally succeed in evaluating reliably the tendency in the level's pattern.

Section 2. Preventing and Combatting Ice Jams

The struggle with ice dam formation on rivers can be conducted, just as the countermeasures against ice jams, by two approaches:

1) by way of adopting preventive measures;

2) by eliminating the ice dams which have formed.

In this context, since the process of ice dam formation is incon­ ceivable without the slush formation process, it is necessary to influence both processes.

- 95 - In the development of the measures which are necessary for averting the formation of dams and the combating of their development, it is neces­ sary:

1) on the basis of an analysis of the possible combination of the main factors determining the formation and development of ice dams, to pro­ vide a forecast of the locations and time of formation of an ice dam, review the hydrometeorological features of the system from the viewpoint of current speeds, air temperature, wind direction and speed and morphology, and

2) in the case of an adequate of extent of study of the system and .the presence of data concerning the time and location of the dams' formation during the preceding period, we can base our forecasts on actual data.

The techniques of preventing ice dams can include the artificial establishment of such combinations of the basic factors under which the process of ice formation in a water basin and the water flow would proceed in a direction either excluding the slush formation or excluding its deposition.

As we indicated above, the basic factors determining the ice process include current speed, temperature conditions and channel morphology. Of the factors enumerated, we can influence to a more or less full extent the velocity conditions in the flow and the morphology. The thermal streamflow conditions depend on meteorological conditions which man is not yet able to influence; therefore, it is possible to modify the thermal aspects of the flow within certain limits.

Proceeding from this, we differentiate the following groups of methods for controlling the flows for purposes of combating the ice dams (cloggings caused by slush or bottom ice):

a) hydraulic; b) thermal, and c) mechanical.

The hydraulic techniques include the methods of developing those flow velocity conditions at which slush formation or the deposition of slush under the ice will not take place. This can be achieved by the construction of hydroengineering complexes, the installation of temporary structures, and by the conduct of straightening operations.

The thermal methods are those based on the introduction of additional heat into the flow, a decrease in the heat release from the water and by a more efficient utilization of the heat reserves in the flow or water basin.

The hydraulic and thermal methods are closely interrelated since in most instances, an efficient thermal regime is developed by the appropriate allocation of the hydraulic conditions. In addition, the hydraulic and

- 96- thermal control methods are the easiest and simplest to implement provided that there are hydroengineering complexes on the river (by way of setting up the required conditions of their operation).

The complete avoidance of ice dams can be achieved in the presence of a HES cascade on the river. For this purpose, it is preferential to build a HES from above downstream. The presence of a station situated farther up­ stream permits a control of the ice regime in the region of building the next stage of the cascade.

The mechanical techniques of counteracting the slush-caused jams are associated with the elimination of such jams which have already formed. They are included in Chapter 7, Section 4.

Section 3. Hydraulic Regulation of the Current to Inhibit Ice Jam Formation

In the hydraulic control of flow, it is necessary to:

a) establish the velocity in the river at which slush formation does not take place;

b) establish the velocity conditions in a given range, at which the formation of a slush-caused jam does not occur;

c) create the conditions under which a slush-related jam is formed and slush accumulates in a safe location; and

d) increase the discharge (and flow speed) for the purpose of breaching or eroding the slush-caused jam, or its shifting downstream.

A decrease in the current speeds can usually be attained by reducing the discharge of water passing through the line of the HES, given the pre­ sence of hydroelectric stations on the river. This measure promotes:

a) the acceleration of the formation of an ice cover on the river, eliminating the supercooling of water and the formation of slush; and

b) a reduction in the quantity of slush in the channel.

A reduction in the stream velocities in the surface flow layer can be achieved by covering the channel by floes, the setting up of booms and by holding back the moving slush with tree branches, etc., which leads to an acceleration of the establishment of the ice cover and the cessation Qf slush-formation in the flow.

In certain cases for curtailing the flow of slush in the region which is subject to protection, it is usually advantageous to create an artificial slush-caused jam (or several such jams) upstream from the sector which is

- 97 - being safeguarded. This is achieved by reducing the surface speeds and with the aid of setting up booms, cribwork, and so forth.

The increase in the flow velocity at the sites of the normal formation of slush-caused jams dangerous for the flooding of the surrounding locality, assures the conditions for the unobstructed movement of slush into the lower less dangerous sectors. In this connection, the current flow rate into the channel should not be less than 1.0 m/sec. Such an increase in speed can be achieved by increasing the discharge (assuming the presence of a hydroelectric station above the sector under consideration), by confining the section (obstructions, shore embankments, etc.) or by straightening and clearing the channel.

The increase in current speeds owing to increasing the discharge rates at an upstream hydroelectric station (the creation of a discharge wave) can also serve as a means for eliminating a slush-caused jam since it forms the conditions favoring its floating up, breaching and partial melting.

Among the hydraulic control techniques influencing the redistribution of temperatures in a flow, we can include the method of exciting transverse circulation in a flow (for example, with the Potapov guiding units). The circulation raises the heavier water masses from the bottom, decreasing the supercooling of the flow and being excited under the body of the slush- caused jam, the water promotes the melting of the accumulated slush.

Section 4. Thermal Regulation of Water Bodies and Currents to Inhibit Ice Jam Formation

1. General Information

The thermal regulation of water basins aid streamflows for avoiding the formation of slush-type jams and the combatting of them includes the development of measures altering the thermal condition of the water for the purpose:

1) of reducing or completely eliminating the slush formation;

2) of influencing a slush-caused jam, already formed, for the purpose of its destruction or the creation of more favorable conditions for application of other control procedures (hydraulic, mechanical, and so forth).

The reduction in slush formation is accomplished by decreasing the dimensions of the zone or the duration of the slush-formation period. Some­ times we succeed in completely avoiding the supercooling of water and con­ sequently the formation of slush.

— 98— In practice, this is achieved by reducing the heat yield from the water Surface or increasing the heat content of the water mass. In the latter case, it is necessary to distinguish the measures in which we utilize the heat contained in the actual water basin (heat from the deep water layers ; adjoining basin sectors, inflows, etc.) and the measures in which we employ the heat of specially heated water pumped into the water basin or the heat from ground water.

The thermal influence on the slush-caused jam, already formed, is conducted by supplying warm water to the slush-caused jam; this leads to a decrease in the body of the slush jam (chiefly from beneath) and in its strength.

The most important raw data in a solution to the question concerning the feasibility of the application of thermal control and the selection of an actual control method include the information concerning the heat con­ ditions of a water object. The methods of planning the thermal conditions depend on the type of water object (river, downstream region, upstream region, and so forth) and have been discussed in specialized literature.

Remark. The practical methods for planning the thermal conditions of reservoirs have been elucidated in "Instructions on the Thermal Design of Reservoirs" [41].

Measures Used in Counteracting Slush Formation

Releases of water from a reservoir. This procedure can be applied for the thermal control of the downstream sectors of hydroengineering com­ plexes and the upstream sectors of reservoirs (assuming the presence of a cascade in the complexes).

The releases of water from a reservoir are accomplished for destroying the slush-formation zone, decreasing its dimensions or transferring this zone to another sector in the downstream area, less risky from the view­ point of a slush-jam formation. Two modifications are possible in the , practical realization of this measure; releases of warm water from the deep layers of the reservoir; and releases of cold water from the reservoir's surface layers. ■

In the first approach, there occurs the warming of the dangerous sector; as a result of this, the supercooling of water in it is partly or completely excluded and the zone of slush-formation is transferred down­ stream (is displaced from the hydroengineering complex).

On the other hand, in the second modification, the edge of the stable ice formation advances toward the hydroengineering complex; as a result, the dangerous sector proves to be covered with ice (totally or partly), which excludes the possibility of the supercooling of water and the formation of slush. In the implementation of this approach, it is necessary to consider

- 99- that in the downstream portion, more ice than normally occurs becomes formed. Therefore, in the case of an earlier opening of the upstream river sectors, complications can develop in the passage of the spring ice-out through the hydroengineering complex (ice jams in the downstream section, etc.).

The thermal calculations with the measure under consideration, include the following:

a) calculation of vertical distribution of water temperature in the reservoir for the time period when the water releases are being con­ ducted;

b) estimation of the variation in temperature over the length, position of the 0°C isothermal line and ice edge in the tail water for the different variations of dumping water from the reservoir.

On the basis of the results of these calculations, with allowance for the design features of the hydroengineering complex (the presence of a spillway, deep or bottom water-conducting openings, etc.) and of economic indexes, we solve the question concerning the optimal method of dumping water from the reservoir.

The dumping of water from the tributaries or upstream sectors of the streamflow. This procedure is utilized for the thermal control of the head and tail waters of the hydroengineering complexes, unregulated (in respect to runoff) rivers, diversion channels, and so forth. (The con­ sequences from this procedure and the related estimations do not differ in principle from those examined above; the sole difference is in the source of water which is being dumped).

Release of heated water (water from heat and electric power plants, specially heated water, warm ground water, etc.). This technique can also be utilized for the thermal control of the head and tail waters of the HES of unregulated rivers and channels, etc. The release of heated water leads to the same results as the drainings of warm water from a reservoir (Sub­ heading 1). We differentiate two methods of releasing the heated water:

1) in the upstream sector, dangerous in respect to the slush- formation conditions; and

2) directly in the dangerous sector.

In the first method of releasing warm water, the hydrothermal cal­ culations include: determination of variation in water temperature over the length of streamflow, location of zero isothermal line and of ice edge for the various temperature values of the water which is being released.

- 100- In the second method of water release, we subject to calculation the temperature of water forming from the intermixing of heated and unheated water. This estimation is accomplished based on the heat balance equation.

Upwelling of warm deep water with the aid of the techniques of air­ pumping and current-forming devices. This approach can be utilized for the thermal control of the upper reaches and also of other water areas when above the endangered sector there are zones with fairly high temperature in the deep and near-bottom layers. The use of air-pumping and current­ forming devices can also be utilized for raising the water from the deep layers of a reservoir to the water-collecting conduits of a dam and for the subsequent dumping of this water into the lower reaches.

The application of the indicated techniques is feasible, assuming the following (approximate) relationships between the deep water and near-bottom temperature: at depth down to 10 m, temperature above 0.5-0.7°C; at depth greater than 10 m, temperature above 1-1.5°C.

The hydrothermal calculations associated with the utilization of the air-pumping and current-forming method include:

a) calculation of the vertical temperature distribution in order to disclose the zone with adequately warm water; and

b) calculation of the parameters of the installation exciting the water circulation.

The methods for the designing and practical utilization of the installations have been described in the book written by V.V. Balanin, B.S. Borodkin and G.I. Melkonyan.

Reduction of heat emission from a water surface. The reduction of heat emission from an open water surface can be attained chiefly by reducing the wind speed. For this purpose we can recommend artificial shelters, enclosures, tree plantings, and so on. Usually these techniques provide an effect on small water areas.

Acceleration of formation of an ice cover. This measure can be achieved mainly by controlling by hydraulic flow conditions (Section 3 of the present chapter):

Measures for the Elimination of Slush-Caused Jams

In view of the limited information concerning the practical appli­ cation of thermal control for counteracting a slush-type jam which has formed, the measures discussed below should be regarded as experimental.

The measures for counteracting a slush-type jam which has formed include the delivery of heated water into the jam. For the obtainment of

- 101- heated water, we can utilize special shore-based or floating installations, dumping of water from the heat and electric power plants, industrial enter­ prises, etc.

The required amount of heat is found from the condition of disrupting the bonds between the slush particles and hence decreasing the strength of the slush-type jam. The location of supplying the heat to the jam is deter­ mined by the dimensions of the zone, over the extent of which the temperature of the unheated water, being released, falls to 0°C. In a number of cases, the release of warm water should be conducted in several places.

On small rivers with the partial plugging of the channel by slush and also assuming the small dimensions of the slush-type jam, the release of warm water can be performed for the purpose of a partial heating of the slush from under the jam and increasing the transporting capability of the channel.

The elimination of slush-type jams, which have formed, by supplying heat to the jam's body should be combined with the employment of explosions, which when utilized individually are not very effective. The elimination of slush-type jams with the use of explosives has been discussed in Chapter 7, Section 4.

Unfortunately, the slight experience in combatting slush-type jams makes it impossible for us to recommend any more detailed data concerning the application of various methods.

— 102— BIBLIOGRAPHY to RECOMMENDED PRACTICE FOR COMBATTING ICE JAMS

[1] Angelopulo, P.P., "Dynamics of Ice Jams on Northern Dvina River in Region of City of Yaunelgav," Collected Reports of Riga Hydrometeorological Ob­ servatory, No 6 , 1964* [2] Antipin, V.A., and Karabat, D.P., Podryvnyye raboty pri ledokhode (Blast­ ing Operations During Ice Debacle), Transzheldorizdat, 1944, 1954* [3 ] Antonov, V.S., "Methods for Predicting the Opening of Estuarial Sectors of Rivers Flowing into Laptev Sea," Trudy AANII (Transactions of Arctic and Antarctic Scientific-Research Institute), Vol 209, No 3, 1958. [4 ] Balanin, V.V., Borodkin, B.S., and Melokonyan, G.I., Ispol1zovaniye tepla ^lubinnyk^^vod^vodo^einov (Utilizing the Heat from Deep Water in Basins), Transport, 1964« [5] Bezuglov, A«A>, "Ice Jams on Nemunas (Neman) River," _Trud2_JJ[il_n22i22^2S£ Gosudarg+ypunogo Universiteta (Transations of Vilnius State University), 1959. [6 ] Berdennikov, V.P., "Dynamic Conditions of Ice Jam Formation on Rivers," Trudy GGI (Transactions of State Hydrological Institute), No 110, 1964* [7 ] Berdennikov, V.P., "On a Procedure for Studying the Formation of Slush- Tjrpe Ice Jams," Trudy III Vsesovuznogo Gidrologicheskogo s"yezda (Tran­ sactions of Third All-Union Hydrologic Conference), Vol 3, 1959* [8 ] Bibikov, D.N., and Petrunichev, N.N., Ledovyye zatrudneniya na gjdrostan- tsivakh (Ice Complications at Hydraulic Stations), Gosenergoizdat, 1950. [9 ] Provisional Instructions on Conduct of Explosive Operations During Pas­ sage of Ice Debacle at Railway Bridges. Transzheldorizdat, 1948. [10] Provisional Instructions on Application of Foam Ice As Insulation Under Severe Climatic Conditions. Energiya, 1965* [11] Yestifeyev, A.M., and Pekhovich, A.I., "Dusting the Surface of an Ice Cover As a Technique for Accelerating the Spring Thawing of Snow," Izvestiya VNIIG (Bulletin of All-Union Scientific-Research Institute of Hydroengineering), Vol 65, I960. [12] Yestifeyev, A.M., Regulirovaniye shugovogo potoka na gidroelektrostan- tsivakh (Control of Slush-Type Flow at Hydroelectric Power Plants), Gosenergoizdat, 1958# [13] Zakharov, V.P., and Chizhov, O.P., "On Combatting Ice Jams on Sir-Dar'ya River by Use of Explosives," Meteorologiya i Gidrologiya (Meteorology and Hydrology), No 1, 1956.

- 103- [ 14] Isila, I#M#, "Investigations of Ïce-Jamming Conditions of Northern Dvina and Sukhona Rivers at Velikiy Ustyug City," Information Letter issued by Northern’Administration of Hydrometeorological Service, No 1(24), 1962* [l5] Kamovich, V#N#, Sinotin, V.I#> and Sokolov, I#N#, "Features in Ice Jam Formation on Dnestr River# Possibility of Estimating the Jam-Caused Levels," Trudy Koordinatsionnykh Soveshchaniy po Gjdrotekhnike (Transac­ tions of Coordinating Conferences on Hydraulic Engineering), No 56, Energiya, 1970* [lô] Kamovich, V#N#, "Effect of Intensity in Rise of Vater Level on Ice Jam Formation and Possibility of Predicting the Maximal Jam-Related Levels on Dnestr River," Transactions of Coordinating Conferences on Hydraulic Engineering, No 56, Energiya, 1970# [17] Komov, N#I#, "Spring Ice Jams in the Lover Reaches of Lena River," Transactions of Arctic and Antarctic SRI), Vol 283, 1968# [18] Konovalov, I#M#, Balanin, V#V#, and Shcherbakova, R#I#, "Ice Jams and Ways to Combat Them," Trudy LIVT (Transactions of Leningrad Institute of Water Transportation), 1965* [19] Koren'kov, V#A#, "Basic Systems and Decisive Factors in Ice Passage During Construction of Hydroelectric Power Plants under Siberian Condi­ tions," Transactions of Coordinating Conferences on Hydraulic Engineer­ ing, No 42, Energiya, 1968# [20] Kravchenko, N#A#, "Formation of Ice Jams on Dnestr River and Technique of Their Study," Transactions of Third All-Union Hydrologic Conference, Vol 3, 1959. [21] Kritskiy, S#N#, Menkel1, M#F#, and Rossinskiy, K.I#, Zimniy termicheskiy rezhim vodokhranilishch rek i kanalov (Winter Thermal Regime of Reser- voirs and Canals), Gosenergoizdat, 1947• [22] Lebedev, P#F#, "Amur River Ice Jams and Their Avoidance," Transactions of Leningrad Institute of Water Transportation, No 30, 1962# [23] Linenko, D#, "Instructional-Procedural Exercise with Sergeants on Topic *Blasting of Ice and Ice Jams1," Voyenno-Inzhenernyy Zhurnal (Military- Engineering Journal), No 3, 1950# [24] Liser, I#Ta#, Vesenniye zatory l*da na rekakh Sibiri (Springtime Ice Jams on Rivers of Siberia), Gidrometeoizdat, Leningrad, 1967* [25] Mishel*, B#, Static Equilibrium of Jams During Ice Passages," Trudy XI Kongressa MAGI (Transactions of Eleventh MAGI [expansion unknown] Congress), Vol 5, 1965* [26] Myasnikov, M#V#, "Ice Jam Phenomena on Irtysh River; Preventing and Combatting Them," Transactions of Leningrad Institute of Water Transport­ ation, No 30, 1962# [27] Instructions from Central Board of the Hydrometeorological Service, No 10, Part 1# [28] Orlov, P#A#, "Yenisey River Ice Jams; Preventing and Combatting Them," Trans# of Leningrad Institute of Water Transportation, No 30, 1962#

- 104- [29] Orlov, P.A., "On Question of Formation and Destruction of Ice Jams," Trudy Akademii Rechnogo Transporta (Transactions of Academy of River Transport), No 1, 1952* [lO] Parize, E., Osse, R., and Gan'on, L., "Investigation of Formation and Modification of Condition of Ice Cover and Jams on Rivers," Transactions of Eleventh MA.GI Congress), Vol 5, Leningrad, 1965* [3 1 ] Pastors, A.N», "Technique of Local Forecasts of Ice Jams and Dangerous Phenomena Associated with Them," Procedural Notes of Central Board of Hydrometeorological Service (CBHS), Latvian SSR, 1951» [32] Piotrovich, V.V., "Appearance, Accretion and Disappearance of Ice Cover on Rivers of USSR European Territory," Trudy TSIP (Transactions of Central Weather Institute), No 6, Gidrometeoizdat, 1948. [33] Popov, Ye.G., "Ice Jams and Problem of Counteracting Them," Hydrology and Meteorology, No 8, Gidrometeoizdat, 1968«

[m ] Rudnev, A.S., "Classification of Ice Jams on Lena River," Collected Works of Yakutsk Hydrometeorological Observatory, No 2, Yakutsk, 1969* [35] Handbook on Hydrologic Forecasts, No 4, Gidrometeoizdat, 1963* [36] Rymsha, V.A., Ledovwe issledovaniya na rekakh i vodokhranilishcbakh (Ice Investigations on Rivers and Reservoirs), Gidrometeoizdat, 1959* [37] Sinotin, V.I., and Kamovich, V.N., "Certain Concepts on Combatting Ice Jams Through Bombing and Use of Explosives," Transactions of Coordinating Conferences on Hydraulic Engineering, No 56, Energiya, 1970. [38] Sokolov, I.N., "Effect of Ice Strength on Conditions of Its Passage Via Hydraulic Engineering Structures," Trans, of Coordinating Conferences on Hydraulic Engineering, No 10, Energiya (Energy Press), 1964. [39] Sofer, M.G., "On Conditions of Breaching of Ice Jams on Malaya Severnaya (Little Northern) Dvina River in Vicinity of Kotlas City," Izvestiya Vsesoyuznogo Geograficheskogo Obshchestva (Bulletin of All-Union Geograph­ ic Society), No T, 1967* [40] "Instructions for Determining Ice Loads on River Structures," Special Instructions-76-66. Izd. Literatury po Stroitel'stvu (Publishing House of Construction Literature), Moscow, 1967* [4 1 ] "Instructions on Thermal Calculation of Reservoirs," VSN-18-68, 1969* [42] Fayko, L.I., "On Reasons for the Stability of Ice Jams in Northern Rivers," Hydrology and Meteorology, No 6, 1968. [4 3] Fedorov, M.K., "Ice Jam and Slush-Type Jam Occurrences and Their Develop­ ment on Lena River," Trans, of Arctic and Antarctic SRI, No 204, Lenin- grad, 1956• [44] Cherkenev, A.I. et al., Prakticheskoye posobive no proizvodstvu vypravit- el'nykh rabot na vnutrennikh vodnykh putyakh (Practical Guidebook to Performance of Straightening Tasks on Inland Waterways), Lenizdat, Rechnoy Transport (River Transport Press), 1961.

- 105- [4 5 ] Shadrin, G*S*, n0n Question of Formation of Ice Jams in Tail of Reservoir," Trans* of Coordinating Conferences on Hydraulic Engineering, No 17, Energiya, 1965* [4 6 ] Shatalina, I*N*, and Spetsov, F*A*, "Experience Gained in Use of Chemicals to Weaken the Strength of Ice," Trans* of Leningrad Institute of Water Transportation, No 16, 1963* [4 7 ] Shulyakovskiy, L*G., and Yeremina, V*D*, "On Procedure for Forecasting the Maximal Ice Jam-Caused Levels of Water (on Tributary of Tom’s River)," Gidrologiya i Meteorologiya (Hydrology and Meteorology), No 1, 1952* [48.] Shulyakovskiy, L*G*, "On the Prediction of Ice Jams During Opening of Rivers," Transactions of Central Weather Institute, No 8, 1948.

MASTHEAD

METODICHESKIYE UKAZANIYA PO BOR*BE S ZATORAMI I ZAZHORAMI L*DA (Recommended Practice for Combatting Ice Jams)

VSN 028-70 Minergo USSR

"Energiya" (Energy Press), Leningrad Branch, 151 pages with illustrations*

Editor Ye* M* Deliy

Released for production: 17 September 1970* M-15559 Signed to press: 11 September 1970* 9*4 printed sheets Order No* 471* Print run: 2500

Price 71 kopecks

Printing House of All-Union Scientific Research Institute of Hydroengineering imeni B#Ye* Vedeneyev Rotaprint* Leningrad, K-220 Gzhatskaya Ulitsa, 21

- 106- Unclassified

DOCUMENT CONTROL DATA -RAD (Sacurity classification of titla, body of abstract and indexing annotation must ba antarad whan tha overall raport is classified) 1 ORIGINATING ACTIVITY (Corporate author) 20. REPORT SECURITY CLASSIFICATION USACRREL Unclassified Hanover, New Hampshire 03755 2b. GROUP

3. REPORT TITLE RECOMMENDED PRACTICE FOR COMBATTING ICE JAMS

DESCRIPTIVE NOTES (Typ* ot raport mnd Inclusive dmtas) Draft Translation ______». a u t h o R(S) (First hams, middl0 in itia l, la s t name)

V. I. Sinotin et al.

7b. NO. OF REFS 6. R E P O R T D A T E 70. T O T A L NO. O F PAC ES July 1Q£_ AS_____ ..m i. 90. ORIGINATOR'S REPORT NUMBER!*» 8«. CONTRACT OR GRANT NO.

b . PROJECT NO. Draft Translation 400

9b. O T H E R r e p o r t NO(S) (Any other numbers that may be assigned thla raport)

10. DISTRIBUTION STATEMENT

Approved for public release; distribut ion unlimited.

12. SPONSORING MILITARY ACTIVITY 11. S U P P L E M E N T A R Y N O TES

13. A B S T R A C T

Ice jams are inseparable occurrences in the annual cycle of the life of many rivers. Ice jams are typical of most USSR rivers. They represent a serious danger for two reasons: in relation to the floods which they cause and the possibility of destruction of various hydraulic engineering structures by ice. The floods caused by ice jams compel us to transfer to safe locations the large industrial objects and increase the cost of building hydraulic engineer­ ing and other structures. Every year, the ice jams inflict tremendous losses on the national economy while in individual unfortunate years, these losses increase by many times. In the compilation of these guidelines, we have utilized the experience accumulated in the USSR for the control of ice occur­ rences and combatting the ice jams which have already formed. Since the jamming of ice is regarded as the most dangerous phenomenon, the greater part of the suggested "Recommended Practice" has been devoted to ice jams.

1. Aerial surveys 6. Ice formation 2. Dusting 7. Ice jams 3. Explosives 8. Ice thermal properties 4. Ice breaking 9. River ice 5. Ice forecasting 10. Thermal effects

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