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Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Remote sensing of flow characteristics of the strait of Öresund 
L.Jonsson 
Dept, of Water Resources Engineering, University of Lund, Sweden 
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ABSTRACT: The strait of Öresund is located in a densely populated region and subject to many activities. Thus, 
it is important to understand the flow characteristics of the strait properly. The paper presents results of the 
use of NOAA and Landsat imagery for exracting information on the large-scale flow pattern and the possibility 
of distinguishing certain flow phenomena. These findings are discussed in relation to known properties of the 
hydrography of Öresund. The remotely sensed flow information is also discussed as far as numerical modelling of 
the flow in Öresund is concerned. 
RESUME: Le détroit d 1 Öresund est situé dans une region populeuse exposé a beaucoup d'activités. Ainsi c'est 
important de savoir les mouvements de l'eau profondément. Cet article present des résultats de l'utilisation de 
NOAA et Landsat data pour l'extraction d'information sur la circulation a grande échelle et sur la possibilité 
de découvrir certains phénomènes hydrodynamiques. Ces résultats sont discutés en relation avec la nature de 
l'hydrographie d'Öresund. L'information d'écoulement obtenu avec télêdetéction est aussi discuté en relation 
avec des modèles numériques d'écoulement en Öresund. 
1 INTRODUCTION 
Knowledge of hydrodynamic processes and circulation 
patterns in coastal waters is important when conside 
ring resource or quality aspects of the waters or in 
connection with technical/constructional measuers in 
the coastal zone. Data on large-scale water circula 
tion by means of satellite imaging provide one type 
of information which could be used either directly 
or in connection with numerical flow models for in 
creasing this knowledge. This paper discusses the use 
of NOAA and Landsat data from the strait of Oresund. 
The study has been made possible by the support of 
the Swedish Space Corporation, the Swedish Natural 
Science Research Council and the University of Lund. 
2 BACKGROUND 
The strait of Öresund forms one connection between 
the southern part of the Baltic Sea and Kattegatt 
(Fig. 1). The length is approximately 100 km and the 
width 10-20 km. 
The flow in the strait is rather complex and at 
times one could distinguish three different water 
types - Baltic water with salinity S = 8-10 o/oo, 
Kattegatt surface water S = 18-24 o/oo and Kattegatt 
bottom water S = 30-34 o/oo. The surface flows to 
the north 66% and to the south 34% of the time mainly 
due to wind and pressure induced water level diffe 
rences between Kattegatt and the Baltic. The most 
common overall flow could be described as a two-layer 
flow situation with northbound surface flow and 
southbound bottom flow. However, the bottom flow is 
normally blocked by the shallow-8-10 m - depth in the 
southern part of the strait. Thus one could think of 
Öresund as an estuary for the "river" Baltic most of 
the time (HarremoBs et al 1966). The main types of 
surface flow patterns based on (rather scarce) field 
measurements are shown in Fig. 1. 
Öresund is bordered by densely populated areas im 
plying a heavy demand on the coastal water for a num 
ber of sometimes conflicting uses. This is one rea 
son, besides purely technical aspects, why detailed 
investigations of the consequences of interferences 
with the coastal waters are often needed. Thus a num 
ber of studies have been performed involving knowled 
ge of and consequences for the flow behaviour in more 
or less detail. In several cases numerical modelling 
of the flow has been used. In other cases the prob 
lems have been approached by means of physical model 
ling, prototype simulations or rather simplified cal 
culations. Some examples are given below (ref. Fig. 2) 
A - an intended railway tunnel on the bottom of the 
strait. Risk for blocking of salt, nutritious bottom 
water. Ecological consequences. Numerical models 
based on vertically or laterally integrated hydrody 
namic equations. 
B - planned, extensive land fillings which might 
affect water exchange, navigation, erosion. Studied 
by means of vertically integrated (shallow water) 
flow equations. 
C - discharge of cooling water from nuclear power 
Figure 1. Large-scale flow pattern in Öresund. 
Northbound flow.