Detection of major river bed changes in River Ebro (northeastern Spain

Espejo, R.

Roquero, C.

Torrent, J.

English

The application or ERTS-1 data to determine the major river bed changes of the Ebro River in northeastern Spain is discussed. Image quality was good enough to permit a clear identification of the river course and bands MSS 5 and 7 proved to be the most useful for this purpose. Reflectance for band 5 was high due to the high sediment content of the water and sufficed to identify the river. Features like bodies of water related to old channels and depressions were only apparent in band 7

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'Paper W 2 
DETECTION OF MAJOR RIVER BED CHANGES IN THE RIVER EBRO 
(NORTH-EASTERN SPAIN) 
R. Espejo, J. Torrfnt and C. Roquero, E. T. S. de lngenieros ~ ~ r d n o m s s  
f Universidad ' Politecnica de Madrid) 
ABSTRACT 
The River Ebro is the most important water course in 
Spain crossing the Iberian Peninsula in a south-eastern direction 
from Central North to the Mediterranean Sea. 
A study has been undertaken to evaluate major r iver bed 
changes over a distance of 30 Km. either side of the city of Zara- 
goza. Data, a s  far  back as  1890 have been used showing that mean - 
ders a r e  fairly active thus causing a noticeable repercussion on 
the use of nearby agricultural lands. 
Results make i t  ; ossible to estimate future trends in  mean - 
der evolution. 
1. INTRODUCTION 
The River Ebro i s  the most important water course in Spain 
Along i ts  927 km. path from the Central-Northern part  of the Iberian 
Peninsula to the Mediterranean Sea i t  collects the waters of the 
southern slopes of the Pyrenees and ends in a large delta of about 
400 sq. km.. Mean discharge a t  i t s  mouth is about 600 c. m. jsec. 
For  many centuries the delta has been building up a t  a quick rate 
thanks to an abundant supply of sediments wich have been caused by 
intenae anthropic erosion. 
The zone of the preeent study corresponds to the middle part  
of the course and and centers around the city of Zaragoza (Fig. 1). 
An approximate length of 60 km, has been selected leavlng the city 
707 
PRECEDING PAGE BLANK NOT FX.+Mka i 
.z 
Original photography may be purchased from: 
EkOS Oata Center 
10th and Dakota Avenue 
Sioux Falls, SD 57198 
https://ntrs.nasa.gov/search.jsp?R=19730019550 2020-03-17T08:46:14+00:00Z
Fig. 1. Map of situation 
a t  i t s  center.In thi,; area  the river flows cutting a complex sequence 
of terraces, usually limited by Miocene s e d i m ~  . ~ t s  (gypsiferous marls)  
Selected areas  that had historically showed meander activity 
were examined by means of topographic maps scale 1:50.000 
correspondig to the years 1.892 and 1.920 (1) and aerial  photographs 
at  scales 1: 45,000 ( USAF - A, 1946 ) and 1: 32,000 ( USAF - B, 
1956 ). Thus a clue was obtained a s  to the direction of river changes. 
Then the available ERTS-1 imagery ( MSS 4,5,6,7, 25th September, 
1972 ) was used to see  the evolution in the last  15 years. 
Image quality was good enough to permit a clear identification 
of the river course and bands MSS 5 and 7 proved to be the most 
useful for this purpose. Reflectance for band 5 was high due to the 
high sediment content of the water and sufficed to identify the r iver.  
Howevel other features like bodies of water related to old channels 
and depreersions were only apparent in band 7. 
3. MEANDER EVOLU'rION 
Eventual floods were a constant danger in the histary of 
the River Ebro, but hazard has heen gradually reduced thanks to 
a ser ies  of dams built during the last 50 years. River activity 
remains nevertheless intense and, continuous action can be seen 
in meander dynamics. 
Several zones of the study a rea  havc- rivet. channels that 
have been abandoned in the las t  15 years. Figure 2 shows a typ- 
ici.il case in which a major variation in the course of the r iver  is 
observed. Mean yearly desplacements a r e  a s  high a s  30m., the 
greater activity obviously related to minor floods and seasonal 
peaks. 
4. THE IMPACT O F  RIVER DYNAMICS 
Fluvial deposits a r e  the best agricultural lands of the area 
a s  surrounding Miocene sedimerits have given place to soils 
characterized by high salinity and shallowness. As a consequence 
of this,  irrigation schemes were established i~ the a rea  long ago 
and have, since then,undergone (: tnges due to r iver  channel i 3 -  
placements. These changes go, tc our knowledge, a s  tar s 
the f~ur teen th  century. 
Demographic pressure  adds to the good quality ii ~ u v -  
la1 deposits to cause the intense cultivation of not only ter races  
but recent alluvium. It has been estimated that, due to r:ver act- 
ivity, 1500 Ha. have disappeared for agricultural purposes and 
900 Ha. brought under cultivation in the lost  80 years. 
It  is expected that repetitive coverage by means of sat-  
ellite can help monitoring r iver  changes in the future thus sup- 
plying valuable information to local authorities, which will  be able 
to take primary decisions about defence works, irrigation schemes 
etc. Characteristics of ERTS-1 imagery will also ' -~ct  useful to 
geographers anld geomorphologists so a s  to appraise the overall 
variations over a long distance of the r ive r  course. 
Another point of interest a r i ses  from the possibility that 
band MSS 7 also shows small  bodies of water. Therefore i t  unll 
be feasible to detect, a f ter  flooding especially, the repartition of 
areas  that a r e  depressed o r  have a slow drainage. An example 
of this has been included in Figure 3 which shows small  water- 
filled depressions in an old river channel. 
FIG. 2 .  AN EXAMPLE OF MEANDER EVOLUTION 
ERTS-1 imagery is Plso intended to serve a s  a source 
for the detection and selectioa of areas of newly deposited alluv- 
id niaterials. These will be taken a s  pilot zones for the study 
of initial soil forming processes, acd compared to analogous cases 
in other rivers were research in soil age hiis been undertaken. 
REFERENCES 
(1) Mapa Agron6miccr Nacional. Comarca de Zaragoza. 
Memoria ( Tomo I ). Ministerio de Agricultura, Madrid, 1.950. 
FIG 3. DETECTION OF A WATER-FILLED OLD RIVER 
CHANNEL 
--  pp 
a) Aerial photog.%ph 


Detection of major river bed changes in the River Ebro (north-eastern Spain)

DETECTION OF MAJOR RIVER BED CHANGES IN THE RIVER EBRO 
(NORTH-EASTERN SPAIN) 
R. Espeio, J. Torrent and C. Roquero, E. T. S & Ifqmikms Agbwumrs U n i e  
&lidmica de Mairk! 
ABSTRACT 
The River Ebro is the most important water course in Spain crossing the IkM 
Rtninsula in a soutkastern direction from - Central Nor* to the #edit- Sea. 
A study has been undertaken to evaluate major rirw bed - chPnges over a distance of  
30 h either side of the city of zamgoz~ Data, as far back as 1.890, have been used showing 
that-meanders are faily acthc thus causing a noticeable re- on the use of the nearty 
agrkcltw-rl lands 
Results mate it Wbk to estimate future trends in meander evolution. 
https://ntrs.nasa.gov/search.jsp?R=19730008738 2020-03-17T08:01:20+00:00Z


Detection of Major River Bed Changes in the River Ebro (north-eastern Spain)

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