1. I . E herk heuli dze

considerable mixing of material composing the river bed takes place and the roughnesscoeffi cient may vary greatly. As the Chezy formula introduces the square root of theslope, even à 100 fold change of slope may be compensated by 10 fold change in theroughness coeffi cient, and evidently, the recommendations, which are accepted, areclose to actual values.

Est im at ion o f basic character ist ics of m udfl ows (" âå1" )

1.1. K herkheulidze, Transcaucasian Hydrometeorological Research Institute,Tbilisi, USSR

û ì ì ëêò: À method for estimation of maximum discharge àï 4 volumes of l iquid and solidmudfl ows (local ï àò å " âål ") is discussed.

The volume of the sel may greatly exceed the volume of the init ial rainfall or snowmelt ï ø î édepending upon the degree of porosity and preliminary saturation with water of fr iable soils onthe watershed.

The possible l imits of solid content of the sel are discussed. Characteristic examples of twowatersheds in the A lps and of à watershed ø the Caucasus are given.

The relationship of the maximum and mean velocity of sels and their width, depth and totalstatic and dynamic pressure on obstacles are given.

Áî ò å considerations on plott ing the discharge hydrograph are listed.The proposed relationships result from elementary analysis of the two-phase " ground-and-

water " system and, from correlation analysis of 40 actual measurements (G. Beruchev and

Î . Syniavski), maximum velocities of the sels ranged from 14.0 to 22.0 ò /sec., volumetric weightfrom 1.67 to 2.29 t/ò ç, mean stream depth from 0.10 to 11.2 ò and longitudinal channel slope

from 3.8 to 26%.

êéâãþì é : L 'auteur propose une máthode pour calculer le dábit maximum et les volumes du d6bit

l iquide et solide des âÛåü (nom local pour les avalanches boueuses ou laves torrentielles). 11 estd6montr6 que le volume d'un âÛå peut largement dápasser lå volume init ial ñÃáñî è1åò åï ã pluvial

ou nival d6pendant du degr6 de ðî ãî â|16 et de saturation práalable des sols friables dans le bassinversant .

Les limites possibles de la phase solide contenue dans le âÛå sont examin6es.On mentionne des exemples caractáristiques des bassins versants à÷åñ âÛåâ dans les A lpes et au

Caucase.On donne des dápendances pour 1'estimation des vitesses maximales et moyennes des âÛåâ, de

leur largeur et profondeur et de leur pression totale statique et dynamique sur un obstacle.Puis sont äî ï ï áåâ quelques ñî ï âÛáãàã|î ï â pour la construction de 1 hydrogramme du âÛå.Les dápendances ðãî ðî â6åâ r6sultent de Ãàï àlóâå 616mentaire du systbme à deux phases « sol-

eau » et de Ãàï àlóâå correlative 4å 40 mesures en nature (G. Beroutcheff et G. Syniavsky) desvitesses maximales des seles (4å 1,40 à 22,0 ò /sec.), du poids volum6trique (de 1,67 à 2,29 t/ms),

de la hauteur moyenne du torrent (4å 0,10 à 11,2 ò ) et de la pente longitudinale (de 3,8 à 26%).

We defi ne à mud fl ow (sel, sil , selav, ruff , nant, mur, etc.) as an open channel torrentof à short duration with sharp peaks; it is composed of water or mud and à large amount(up to 60% of its total volume) of solid materials (âî called water-stone, mud-stone or

940

Esti mati on of basi c characteri sti cs of mudf iotos

mud-fl ows). These solid materials can enter à stream either as the result of intensiverunoff due to storm rains, abrupt snow melting, breakdown of à moraine barrier or glacierlakes and other reservoirs, or seismic activity, or if valley slopes and stream channelsof à drainage basin are formed of readily erodible materials, or if there are largeaccumulations of weather ing products, or when river bank and bed slopes are steepenough to ðàâè à mud fl ow (sel) of defi nite volume and concentration. The abovedefi nition coincides in general with that î Ë .Ó. Bogolubova [1] and Chebotarev [2] butis somewhat enlarged and detailed by the author. I t comprises all possible sels, whichmay cause severe damage in mountainous and hilly regions, as well as in condit ions ofhills and plains (ravine and "wadi " scouring, for example, in the Sahara). Sels may

diff er widely in their saturation with solid materials, lithological and fractional compositionand the character and velocity of movement . But they follow the laws of à fl owing solidmass movement with à water content exceeding the limit of fl uidity for the solid phaseof the sel . The powerful and disastrous character of sels depends in great measure on oneor other unfavourable combination of numerous diff erent factors aff ecting them and arequite uncertain.

Solid material contents in sels may be defi ned in terms of volume, weight or othercharacter istics (both dimensional and non-dimensional) interconnected by defi niterelations. I t is always necessary to show clearly which of the possible character istics isbeing introduced in à formula or à table, to avoid misunderstandings; ø the literature onsels or sediment transport there are instances where such an explanation was not given.I f T and yr are respectively the volume and the volume weight of solid materials in àcompact body; ÝË and y~ are the same for the liquid phase of the sel (water), then thesolid Âöèê ratio is

— Óò(1 Ð) Óò Ð Óò Óå

The volume concentration of solid materials:

p o

T + 35 1 + p ( 1 + p) y, + ÐÓ~

The weight concentration of solid materials: Óñ ÓÙ Vr Óù ( 2 )

ÒÓò ~Óò 0î Óò

Tyr + 3Hy~ (1 S) Óù + ~Óò Ðî Óò+ Óù

M uddiness of the stream : ÐÓò (Óò Ð) Óù + ÐÓò Óò(Ó Óù ) Ó(Óò ~ )

ÐÓù Óò Ð- î Óò Óò(Ó. — Ó,ù )Ð = = ~Óò =

ò + ÿ ( 1 — ð ) Ó, + ÐÓ„ , 1 + ð , Ó, — Ó, „Volume weight: (4 )

ÒÓò + Æ Óy~ + S (yr y )Ò+ ,'Æ (1 — Ð) Óò + ÐÓù

Óù + Ðî Óò Ð= Ó„ , + — (Ó, - Ó,„ ). (~)1+ Ðî Óò

9 4 1

1. 1. K her k heu li d ze

ÒÍ Å SA T U R A T I ON L I M I T OF SEL S W I T H SOL I D M A TER I A L S

The theoret ical l imits of the volume concentration for turbulent sels by Ì .À . Velikanov[3]are for

óò — — 1,0 t /m ; S = 0,50 ; for óò — 2,65 t/m ' ; S = 0,41;

this ð = 0,65; ð = 1,09 t/ò ' and ó, = 1,68 t /ò ' .

L imits given by Sokolovsky [4]

S = 0,38; ð = 0,62; ð = 100 t/ò ~; ó, = 1,63 t/ò

are similar to those of Egiasarov [5]

S = 0,36; ð = 0,60 ; ð = 0,96 t/m ; ó, = 1,60 t/ò ~.

It connects the degree of saturation with solid materials and the longitudinal slope ofthe channel . As the values of p and ó, given by Shtiny do not correspond to each otheraccording to dependence (3), the author has re-calculated the values of ó, using the weightconcentrations of Shtiny as the initial ones (table 1).

T A B L E 1

9 1Ï é

M i n i m u m  ó s h t i n y Re-calculated

M aximuth ' M inimum M aximum

1 5

2 0

2 5

3 0

3 5

4 0 Ó ñ Ð Ó~ 0 .2 6 0 .4 5 1 . 3 4 0 . 5 0 1 . 3 4

0 . 3 4 0 . 5 0 1 . 3 8 0 . 6 0 1 .4 6

0 .4 2 , 0 . 5 5 1 .4 2 0 . 6 5 1 .4 9

0 . 5 0 0 . 6 0 1 .4 6 0 .6 8 1 . 5 2

0 . 5 7 0 . 6 5 1 .4 9 0 . 7 0 1 . 5 3

0 . 6 4 0 . 6 5 1 .4 9 0 .7 0 1 . 5 3 Óñ Ó ñ 1 . 3 9 1 .4 5 1 .4 5 1 . 5 2 1 . 5 2 1 .6 8 1 .6 0 1 .7 3 1 . 6 8 1 . 7 7

1 . 6 8 1 . 7 7

The re-calculated values of ó, are higher than those in Shtiny's, and approach 1.77.From the author ' s calculations and especially from detailed fi eld researches of sel

rivers in Yugoslavia by Cxavrilovitch [6] it is seen that Shtiny's tables characterise suffi -ciently accurately the probable saturation limits with solid materials of highly erosivebasins, but give larger limits (to 4-5 times) for medium, poor or very poor erosive basins.At the same time concentrations of solids considerably higher than those given inShtiny's table are found to occur .

Ñ . Beruchev on the river Durudj u (East Georgia) and D . Siniavsky on the riverK ock-Cheka (K azakstan) observed sels with volume weights to 2.00 t/m~ and even ò î ãå.K eller [7] refers to the data of Ì . Parde that à sel in Faucon in the Alps occurring onthe 18 August 1876 carried out 169 000 m~ of debris with the water volume of 65 000 m~.With à coeffi cient of porosity of large block debris (boulders, pebbles, gravel , sand withsmall admixture of fi ne fractions which is characteristic of mud-stone streams) of theorder 0.51-0.66, when ó , = 2'65 t/m~ we receive:

with E = 0 51' /Itl = 1 72 S = 0.63; ó, = 2.04 t/m~

with ÿ = Î .áá; / le = 1.56; S = 0.61; ' ó, = 2.00 t/m~.

Obviously one ò àó accept as the limit of saturation of sel mass with solid materialsthe volume concentration S = 0.60, and respectively pe = 1.50, ð = 0.80 and

9 4 2

Esti mati on of Áàò ñ char acteristi cs of mudp ows

ó, = 1.99 è 2.00 t/m~. This largest l imit may take place only at intensively eroded

high mountainous basins, with very steep channels and valley slopes, ø zones of clayloamy soils. À great deal of research work should be conducted to defi ne more exactlywhich relations exist between limit concentration and slopes, the degree of erosion andother factors.

M A X I M U M A N D M EA N V EL OCI T I ES OF SEL S

Up to the present time in the literature on sels there is l ittle, if any, adequate informationavailable on velocities of sel fl ows with reliable data on their parameters (width, maximumand mean depths and velocities, concentration, granulometrical composition andlongitudinal slope).

Therefore the data obtained by G. Beroutchev on maximum velocities of sel fl owand of channel parameters at the river Durudj a and data obtained by Siniavsky for theriver K ock-Cheka are of great value. For the river Durudj a there are also some dataof hydrometric measurements conducted by the Hydrometeorological Service of Georgiaon the debris cone. The observations of Berutchev and Siniavsky made at 43 points,embrace à wide range of parameters for sels: the maximum velocities are measured inthe range from 1.40 to 22 m/sec.; the volume weights of the sel — from 1.67 to 2.29 t/m ;the mean depth of the stream — from 0.10 to 11.2 m and the longitudinal slope of thechannel from 3.8 to 26 per cent. Therefore the fi eld data given ø this paper includenearly the total range of changes of computed characteristics for sels. Correlation analysisof these data leads to the following empirical expression for the maximum velocity ofsels; the coeffi cient of determination is high (r = 0.95 ~- 0.04; ct = + 19.8%).

1/ 1 0 7 5 / 10 , 6 5 0 , 3 3( 6 )

Equation (6) is not improved by taking into account the infl uence of weight concen-tration of solids in the correlation analysis; on the contrary, the average square rootmean error increased to ~ 31.0%. Thus it is ðî âç1Ûå to speak of practical invariabilityof velocity for à sel regarding to the concentration of the solid phase in the range of ó,studied i .å. 2.00 t/m~. On the basis of indirect observations Beruchev, Siniavsky and some

other investigators recommended introduction of à coeff icient of order 0.5-0.55 whenconsidering the transition of à sel from à maximum velocity state to an average one.This value as well as large values of velocity correction (0t = 1.8-2.0) obtained in fi eldinvestigations quite satisfy the power relation for the above mentioned velocity profi le( V, Ð ,„) 0,5 and à = 2 for the model of parallel fi lament motion. At the presentstate of knowledge, the calculated value of the coeff icient of transition is accepted to beone given by Ü.À . M orosov [8] with the numerical parameter rounded off .

0 3 0 C 1/ 4~ max ( 7 )

From formulae (6) and (7) the following formulas for computation of the averagevelocity and depth of the stream were derived in terms of à given specifi c calculateddischarge (q m /sec) and channel parameters:

0 , 10 62 71 - 0,361 " .0,177

- 0 ,10 60 369 - î 63~~ - î 17 7

( 9 )

9 4 3

1.1. K herk heuli dze

For the maj ority of sections (h/R) ' may be accepted è 1. ÒÜå second calculationof the average velocity of sels using the well-known formula of Chezy-Sribny, takes intoaccount the solid phase:

6 5 R zi ~ i i i 4 ( 1 ð ) ~~~

Proceeding from equation (10) it is ðî çÿ Ûå to derive:

307~î ,4î î ,û (1 ) î ,çî

() 32' go ~î 1 — o i 5(1 ð) — o ( 10 )

( 1 2 )

Rather similar values of the constants and exponents ø both groups of formulasenable us to consider such parallel application to check up on the results of bothcalculations.

POSSI BL E W I D T H OF SEL S I N BR OA D CH A N N EL S

In à large valley mountain streams including sels, either break up into some branchesor fl ow ø à single concentrated channel, bordered with banks having been created bythe stream.

The width of the stream, Â , may be determined using S.Ò. A ltunin's formula, ø

terms of the eff ective diameter, dsii, of sediment ø the channel, about 30% of all thefractions ø the mix having larger diameters:

1 5 ä î ,S

(~ -1- () 07)» ' 1î ,~î ( 1 3 )

STATIC AND DYNA MIC FORCE EXERTED BY THE SELON À NORMAL OBSTACLE

The decision, taken Úó the À1Ì 1ø î ï Conference on sels ø the city of A lma-Ata (1957),that all sel fl ows should be considered to be fl uid î ï åð and âî ø å fi eld investigations onsel velocities enabled the author to use the well developed theory of j et impact whenestimating the impact of à sel mass moving at velocity V, .

I t is possible to obtain the following simple expression of total pressure (averagedover the depth) exerted by à sel on à normal obstacle, water load momentum and staticpressure being taken into account.

PÄ~Ä = 0,10 ó, (5h + Ê ~) t /m ~.( 14 )

This formula is supplemented with the table of pressure values exerted by sel on ànormal obstacle; the table was proposed by P.S. Neporozny and G.Ì . Berutchev.

MAXI MU M DISCHARGES AND VOLU MES OF DEBRISCARRIED OUT BY SELS

Together with eroded outwashed or broken-down soils, çî ë å water contained in soilinterstices enters water courses.

So, the author has introduced an auxiliary dimensionless ratio of the volume of solidmaterials ø à compact body having entered the stream (â ~) to the volume of initial

9 4 4

Esti mati on of basi c char acteri sti cs of mut/f/ o1os

water runoff (w ). T his auxil iary rat io (p ,' ) ò àó be related to the true sol id-l iquid rat io

(ô (>) in the formed sel in such à way:

o rð Q Ð'

1 + äå, p(] ( 1 5 )

W here ä and å, are the coeffi cients of water saturat ion and porosity of so ils enter ing

the stream .Sol id mater ials and the addit ional quant ity of water contained in their pores increase

the volume and stage of à stream . The h igher the stage, the greater is the velocity ofà stream, until à certain l im it of concentrat ion of sol ids has been reached ; à fur therincrease of sol ids ò àó prevent an increase ø the velocity of the sel . The increase øcr oss-sect ion area of the stream , its height , velocity and discharge when loaded w ithsolid mater ials and the addit ional quant ity of water contained in their pores, may be

calculated using the formulae:

ô „ = — ' = 1+ ( 1 + äå,) ô ,] ,Þ ó ( 1 6 )

where:

ttt = 0 for à rectangual channel ;ttt = 0,5 for à parabol ic form ;

ò = 1,0 for à tr iangular form . ñ ~ 1/ ( 1 + m) Ü, ( 1 7 )

ñ , /, ( 2 , / 1 — ð)/ [ 3 ( 1 + m) ]'r' v Vs ( 1 8 )

This f ormula (18) agrees with that of Chezy and Sr ibny which tak es into account theinfl uence of sol id concent rat ion on stream velocity . I n the âàò å way one can wr ite theexpression for p Ä when using any other sel velocity :

( 19)

Then the rat io of total solid discharge in à compact body to the volume of the totall iquid phase (i .å. the average for the per iod when the sel is in its sol id-liquid state) is:

w h e r e Ðé 1 + äå, p )r ( 2 0 )

Wr Nwp l

Ws 1+ äå. ~ )(

the auxil iary solid-l iqu id ratio of the volume of total solid phase, ø à compact body,to the volume of in it ial l iquid r unoff . A ccordingly, the coeffi cient of transit ion f rom thev olume of init ial l iquid runoff to the t otal volume of the sel is:

ô , = l + ( 1 + äå, ) ð '

9 4 5

1 . 1 . K h e r k h e u l i 'd z e

Accept ing that the ordinates (discharges) in the hydrograph of initial òèï î â' increase in

direct proportion to ô and the abscissae (time of rising and fall) are increased ordecreased in proportion to l/t Ä, then l/t , = l/tÄ. The values of transition coeffi cients at àtheoretical l imit for turbulent sels (p0 = 1,0; S = 0,5 and ó, = 1,83 t/m~ atóò = 2,65 t/m~) and at an upper limit of concentration (p0 = 1,50; p = 0,60 andó, = 1,99 t/m~) at diff erent î ã, are given in table 2.

T A B L E 2

V alues of äââÐî

0 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 ,0.65. . .

1.0 0 2 .00 2 .67 2 .86 3 .0 7 3 .33 3 .64 4 .00 4 .44 5 .00 5.72 ,

1.50 2 .50 4 .00 4 .54 5 .2 6 6 .2 5 7 .69 10 .00 14 .2 8 2 5 .0 0

ù 1.0 0 1.59 1.92 2 .0 1 2 . 12 2 .2 3 2 .36 2 .52 2 .70 2 .92 3 ,20

1.50 1.84 2 .52 2 .74 3 .0 3 3 .39 3 .90 4 .64 5 .89 8 .55

1.00 0 .7 1 0 .8 1 0 .8 3 0 .8 6 0 .89 0 .92 0 .9 7 1.02 1.0 7 1. 13

1.50 0 .67 0 .8 3 0 .88 0 .9 4 1.0 1 1. 11 1.2 5 1.4 6 1.87

1.0 0 1.42 2 . 16 2 .38 2 .6 5 2 .9 8 3 .38 3 .88 4 .5 1 5 .35 6 .4 8

1.50 1.6 8 3 .32 3 .99 4 .94 6 .33 8 .54 12 .4 8 20 .89 46 .86

From table 2 one can see that in sel runoff computations it is necessary to determinequite correctly the product î ÿ, the changes of which beyond the limit of 0.40-0.45 exertà sharp infl uence upon the values of coeffi cients. The fi eld determination of î â, in realityis possible only at êî ï Üå points because of the general variety of soils in sel basins ofconsiderable size, Ôå|ò diff erent physio-mechanical characteristics and conditions ofpreliminary water saturation ; such values are averaged all over the basin and the fi nalcomputations may be rather erroneous. Therefore it is of special importance to collectsuch fi eld data as might indicate possible l imits of the value äå, . As an exampleÌ . Parde [9] described how at night on the 13th of June 1829 the glacier "Tete-rousse"(to the south of M onte Blanc) suddenly òÜòå÷ out at à height of 3100 m 200,000 m~ of

water, which in fl owing down the steep slopes augmented its volume 5 times by uptakeof sediment ; in the consequent sel fl ow, 175 human beings perished.

The value of l/t, = l/tÄ = 5,00 from table 2 corresponds, at an upper l imit of p0 = 1,50,to äå, = 0,333. Í åï ñå

1,50= 3,00

1 — 0.333 1,50

andô , = 1 + (10,333) 3,00 = 5,00

Similar examples may be given of sels in the Caucasus. On the 25th of July, 1963,Ñ .Ì . Berutchev measured à ÷åòó large sel discharge (1244 m~/sec, volume weight ofsel mass taken from the stream being 1.90-2.10 t/m~) on the r iver D ouroudgy, the

southern slope of the Great Caucasus. This discharge exceeds that of the maximumpossible rainfl ood for this basin (190 m~/sec) 6.50 times. From table 2: the valuelpQ = 6,50 corresponds to the value of äã, = 0,41 when p0 = 1,50.

On the 23rd of July, 1963 in the headwaters of the r iver Caj artasou (the northernslope of the Great Caucasus) à sel with à discharge of 60m~/sec was formed; after movingdownstream for several k ilometers it reached à value of 350 m~/sec, having increased5.83 times without appreciable infl uence of lateral infl ow. The value of l/t < = 5.83

946

Esti mati on of basi c char acteri sti cs of mudp otos

taken from table 2 corresponds to î ÿ, = 0.38. Accepting for the both Caucasus riversäÿ, = 0.40, the theoretical value of p < = 6.33 will exceed by 7.8%, the real one for theriver Caj artasou and will be less by 2.6% than for the river Douroudj a.

So, for powerful Caucasus sels the calculated values of äÿ, may be rougtdy taken= 0.40, and those for the Alps — about 0.39. I f instead of the upper limit of pp = 1.50for turbulent sels one accepts the theoretical limit value of pp = 1, then the fi eld valuesof äÿ, for the rivers Douroudj a and Caj artasou, as is seen from table 2, may be reachedat the value of äÿ, in the range of 0.60-0.65, and that for A lpine sels — at äÿ, = 0.60.This is à possible limit, as for coarse sediments (boulders, gravel and sand with à smalladmixture of fi ne colloidal materials) which is the case with sel sediments, the ÷î 1ø ï åweight of sediments ranges from 1.6 to 1.76 t/m~, changing à little wi th t ime and the ageof sediments. The porosity coeffi cient changes in the limits of 0.66-0.51.

On the basis of the above three real examples of very powerful sels,at ô å = 1.00., ó, = 1.83 t/m ; äÿ, = 0.60 (the Alps and the Caucasus)at pp = 1.50; ó, = 1.99 t/m~; äÿ, = 0.33 (the A lps) and

äÿ, = 0.40 (Caucasus).

The both computation methods should lead to the ç ë å results for maximum dischargesand volumes of sels, and give similar results for the values of calculated pressure, becausethe increase of volume weight equals the decrease of velocity, when using the formulaof Sribny. I t is extremely desirable to have suffi cient fi eld data, to analyse possible realvalues of ó, and äÿ, for other sels. They should be connected not only with physicaland geographical parameters of the basin, but also with those of probability.

The maximum discharge or the volume of surface waters which are to be taken as àbasis for computation may be calculated either by one of the empirical formulae formaximum rainfall runoff , best suited to the given àãåà; or by est imating the probabledischarge following breakdown of à moraine barrier glacier lake or reservoir .

M EA N A N N U A L V OL U M ES OF SED I M EN T L OA D I N SEL BA SI N S

In the USSR the greatest mean annual sediment load according to Shamov was observedon the rivers Achty-Chay = 1740 m~ km~ and Wahsh = 1280 m~/km~. The rivers ofYugoslavia according to S. Gavrilovitch wash out from 929 to 3662 m~ km~ per year .The greatest quantity is washed out by the river Palaj ska = 3662 m~/km~ per year andZla D olina = 3479 m~ km~ per year . By Hartwagner the stream Schlittenbach transportsin average 1730 m~/km~ per year. Ì àçÿ|ï åÿ | ïàëîòòè that in the storage reservoir ÃÎ èå<ÛFoda in A lgeria 3460 m~/km~ alluviates per year. By Douisaoff in the storage reservoirBig-Santa Anita in the USA 1630 m~/km~ of sediment are transported per year.

According to the same author from calculations made in the USA the possible specifi csediment runoff from the mountain slopes of San-Gabriel amounts to about 3700 m~/km~per year. According to Lockerman from the data given by R. Keller, the sediment runoffof the river K osi in India reaches 1570 m~/km~ per year . I t is interesting to notice thatthe so-called gully sediment sels are able to give the greatest values. P. Salnikov statesthat the specifi c outwash from 2 great gullies in the Transbaikal region for the periodof 25 years equaled 3800 m~ km~ per year. Consequently, the highest values of specifi c

mean annual volumes for sediment runoff may amount (for intensly eroded basins) to3600-3800 m~/km~ per year. The given values are attr ibuted to the volumes of loose bodies.

Though the elementary formulae and constants examined in the report allow (at leastroughly) evaluation of the basic characteristics of sels, the author ' s main aim is tounderline the necessity of extending complex investigations of general geomorphologicaland hydrometeorological characteristics to include physical and mechanical constantsfor soils in sel basins, because such data are seldom available.

94 7

I rt g . Car lo B endi ni

ß Å Ð Å ß Å Õ Ñ Å Á

1. BOGOLUBOVA, I .× . (1951): Sels and their occurrence on the territory of USSR. Gidrometeoisdat,Leningrad.

2. Ñí ââî òëêâ÷, À .1. (1957): Red. Glossary of basic hydrological terms and conceptions,Ci drometeoisdat, Leningrad.

3. × ÿè êëûî ÷, Ì .À . (1949): Dynamic of channel streams. Gi drometeoi sdat, Leningrad.4. SOKOLOVSKY, D .Ü. (1959): River runoff . Gi drometeoisdat, Leningrad.5. EGIAZAROV, 1.V . (1962): Essay on theoretical computation of sediment load of very diff erent

dimensions of particles for à given fl ood hydrograph. À .# USSR, M oscow.6. GAVRILOVICH, S. (1957): Classifi cation of Grdelichke — Clissure mudfl ows and quantit ive

regime of their sediments. Belgrad.7. KELLER, R. (1955): Surface water and i ts balance. " Progress" , M oscow.8. M oaosov , Ü.À . (1966): On the coeffi cient of kinetic energy for natural water-streams.

Gi drotechnicheskoe stroi telstvo. N 5.9. Ðóêî é, Ì . (1964): Inundations — 1Üå enemy of humanity, Couri er Unesco, VI V I I , Moscow.

Üà grande crue du 4 novem bre 1966

Ing. Carlo Bendini,D irettore ñlålÃÛ Èñ|î Idrografi co ñ1å1ÃÀãï î -Pisa

êéâï ì é : Ü'auteur d6crit la grande crue du 4 novembre 1966 en Toscane.

SUMMARY: Description of the famous fl ood of 4 N ovember 1964 in I taly.

Dans les j ournees du 3-4 novembre 1966 un centre cyclonal provenant de ÃÎ èåâ1,qui s'btendait à peu pres de la Mer tyrrhenienne centrale à la region de la ×åï å11å,à provoque des pr6cipitations exceptionnelles qui ont cause, dans les cours ñÃåàè 1ï ãå-ressbs, des crues parfois catastrophiques à÷åñ plusieurs victimes et des dágats ñÃèï åimportance incalculable aux biens publics et prives.

Üà Toscane à åãå concernee presque dans toute son etendue par ce phenomene quietait caracterise aussi bien par ÃàÜî ï ñ1àï ñå des pluies que par la continuit6, 1'intensite

et Ãå1åï ñ1èå de celles-ci .À ce dernier propos il suffi t d'observer la carte des isohyetes (fi g. 1) redigbe en relevant

les precipitations enregistrees entre 9 heures du 3 novembre et 9 heures du 5 novembre.En fait , il s'agit en rbalite, de 25-26 heures de pluie et non de 48 heures comme quel-

qu'un pourrait penser. En dehors de cette periode, les precipitations deviennent tres

faibles car elles ne depassent pas 5% de la quant ite totalisee dans les deux j ours.En examinant plusieurs diagrammes de stations entre les ð1öû ï 1åãåâÿååÿ par le pheno-

ò åï å, 1'î ï peut constater que dans la continuite ò åò å de la pluie on distingue, nettementdeux noyaux de plus grande intensite: le premier, ñÃåï ÷1ãî ï 4 heures avait commenceentre 17 et 18 heures et il etait fi ni entre 21 et 22 heures le 3 novembre; le second,d'une durde ñÃåï ÷|ãî ï 3 heures avait commence entre 9 heures et 10 heures et il etait

fi ni entre 12 et 13 heures le 4 novembre.

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