SECOND INTERNATIONAL SYMPOSIUM ON FLOOD DEFENCE

INTRODUCTIONIn the past decade frequently occurring floods claimed thousands of lives and caused economic loss of billions US dollars. Among them the Mississippi River flood in 1993, the Rhine River flood in 1995, the Yangtze River flood in 1998, the Haihe River flood in 1996, and the storm surges in Bangladesh in 1991 are the most devastating. It is evident that both the frequency and intensity of flooding are increasing.The first International Symposium on Flood Defence in Sep. 20…     

SEVENTH INTERNATIONAL SYMPOSIUM ON RIVER SEDIMENTATION and the SECOND INTERNATIONAL SYMPOSIUM ON ENVIRONMENTAL HYDRAULICS

INTRODUCTIONTheInternationalSymposiumonRiverSedimentation(ISRS)isatriennicalconferenceseriesinitiatedin1980bytheInternationalResearchandTrainingCenteronErosionandSedimentation(IRTCES)inBeijing,China.SuccessfulconferencesinthisserieshavepreviouslybeenheldinBeijing,Nangjing,Jackson,Karlsruhe,andNewDelhi.ThefirstInternationalSymposiumonEnvironmentalHydraulics(ISEH)wasinitiatedandhostedin1991bytheUniversityofHongKong,andwasattendedbysome300delegatesfromthirtycountries.TheSeven…     

CONTRIBUTION A L'ÉTUDE SUR LE TRANSPORT SOLIDE EN SUSPENSION DANS LES COURS D'EAU ET SUR LA DÉGRADATION DU SOL DANS LE BASSIN DU PO

Sommaire

Utilisant les données à la disposition du Bureau Hydrographique du Pô sur le transport trouble en suspension, relevées sur de nombreux cours d'eau pendant différentes périodes qui vont de 1918 à l'année 1960, on a effectué une étude sur la dégradation du sol dans le bassin du Pô.

On a ensuite cherché une corrélation entre la dégradation unitaire (dégradation par mm d'afflux) et l'affluence elle même, après la subdivision en trois classes des bassins du Pô selon leur degré d'érodibilité.

Enfin on a essayé une réélaboration des valeurs de la dégradation moyenne annuelle évaluées d'après le transport en suspension pour tenir compte du transport par entraînement sur le fond et du transport en solution dans les eaux, utilisant et généralisant les données orientatives se rapportant à des situations particulières ou bien à des bassins.     

BRIEF REPORT ON THE SYMPOSIUM ON TANCHENG-LUJIANG FAULT ZONE

The Symposium on Tancheng-Lujiang fault zone held at Weifang, Shandong province on November 1-10, 1980 was organized by the Geological Society of China, accompanied with field trip. The problems of the regional geological investigations, exploratory survey for ores, geophysical prospecting, seismogeology and images interpretation have been thoroughly discussed.All representatives came to following common understanding: (1)Tancheng-Lujiang fault zone is a gigantic fault zone in East Chi     

PRINCIPES NOUVEAUX POUR DISTINGUER CE QUI EST Dû A L'ÉCOULEMENT SOUTERRAIN SUR L'HYDROGRAPHE DES FLEUVES

Abstract

Throughflow has been measured from three soil horizons on a 12 slope with impermeable, bedrock. Storm flow comes from the 10–45 cm horizon and is controlled by the upslope extent of saturated conditions. Base flow comes from the 45–75 cm horizon and is supplied by slow unsaturated flow from the whole soil mass to a small constant zone of saturation.

Differences between input and output stream hydrographs over 270 metres of channel are attributed to throughflow and correlate well with measured values providing a basis for separating throughflow components from the stream hydrograph. Observed stream flows contain no overland flow or ground water flow components. The main basin flood peak is not generated within this control section of channel but is produced in the headwater zone (0.1 km²) by the faster runoff characteristics of the soils in that area and by topographic factors which lead to rapid channel extension.     

RÉSULTATS DE L'ÉTUDE DE L'ÉCOULEMENT DES ALLUVIONS EN SUSPENSION DES RIVIÈRES DE LA ROUMANIE

Abstract

The study is based on the 121 answers to the international survey on ground water recharge published in I.A.S.H. bulletin n° 87.

After generalities about the aims, benefits, type of devices, recharged aquifers and size of plants, are examined:

—The infiltration devices (basins canals).

—The injection devices (wells).

—The economical aspects of realisations.

Diverse statistical correlations are found, and regression formulas proposed, concerning:

—Connections between permeability, size of devices, and the injection or infiltration rate.

—Connection between the annual input and the capital invested.

The synthesis of these datas conduct to results which may be useful to pepare new-projects of artificial recharge.     

QUELQUES CONSIDÉRATIONS SUR L'EMPLOI DES TENSIOMÈTRES

Abstract

The interpretation of tensiometers measurements requires special knowledge of the mechanics of equilibrium of the tensiometer with its environment. The classical concept of response time τ = (1/K′ S) of the system: porous cup (conductance K') and manometer (sensitivity S) can be improved by taking into account the elasticity of the tubing. By analogy one can appreciate the role of entrapped air in the circuit. In general, it is possible to theorically observe the response characteristics of the tensiometer by imposing pressure step in the system and by studying the equilibrium response. Such tests showed certain anomalies of behaviour which can be attributed to very small bubbles of air entrapped to the internal wall of the porous cup.

However, it is necessary to check the response of the tensiometer when it is placed in the soil. This is confirmed by analysis and experiments in a sandy and clayed soils.     

INTÉERÉET D'ÉETUDES HYDROLOGIQUES APPROFONDIES SUR DES BASSINS EXPÉERIMENTAUX OCCUPANT PLUSIEURS MILLIERS DE KM2

Abstract

A relationship of hydrologic variables with stream salinity was determined statistically for two ephemeral streams located in western Oklahoma. The hydrologic variables employed in this study are measures of streamflow, precipitation, anteccedent conditions, and agricultural land use.

The best single estimate of stream salinity was achieved by use of those variables classed as direct measures of precipitation, with the greatest variability in stream salinity (51%) being predicted by maximum daily P, the maximum amount of precipitation received at any rain gage zone in the watershed during one month. Maximum daily P predicts nearly double the variability in stream salinity predicted by flow. Antecedent conditions did not correlate well with stream salinity, except for the variable describing the antecedent stream salinity. Similarly, the areal location of precipitation within the watershed and agricultural land use did not correlate significantly with stream salinity, except for a variable designating the distance between the stream gaging station and the rain gage zone receiving the most precipitation for the month.

The best overall estimate of salinity was given by a multiple regression equation chosen on the basis of a factor analysis. This equation accounted for 65 percent of the variability in salinity and emphasized the contribution of variables classed as direct measures of precipitation. In comparing the two streams, the watershed having the most intensive rain gage network produced the best prediction equation.     

LES DONNÉES SUR L'EAU ACTUELLES ET FUTURES / WATER DATA TODAY AND IN PROSPECT

ABSTRACT

The network density for the estimation of areal rainfall is determined by the method of optimum estimation. This method considers local variations as well as inter-station characteristics of rainfall over an area while assigning weights to gauges for the estimation of areal rainfall. The network density required for different tolerable errors in the estimation of areal rainfall for the months June-September, for the monsoon season, and for the year, was determined for different sized areas over Vidarbha, a meteorological subdivision of India. The errors in estimations of areal rainfall obtained by the method of optimum estimation are smaller than those obtained by the arithmetic mean.