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Remote sensing for resources development and environmental management
Damen, M. C. J.

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
A methodology for integrating satellite imagery and field
observations for hydrological régionalisation in Alpine catchments
Department of Hydrogeology and Geographical Hydrology, Institute of Earth Sciences, Free University, Amsterdam,
ABSTRACT : Years of intensive fieldwork in the N-Italian Dolomites have demonstrated that in complex Alpine
environments predictions of stream runoff and sediment yield for ungauged watersheds require a semi-distrib
uted, physically-based régionalisation model. The physically-based character of the model has to be guaranteed
by detailed field observations, while Landsat remote sensing data can be quite valuable in quantifying the
distributed nature of the model.
A hierarchical régionalisation procedure is presently being applied to the N-Italian Dolomits :
(1) A broad physiographic zone of Permo-Triassic-Liassic rocks has been delineated with Landsat MSS images
(2) Vegetation and landuse units are identified by a supervised digital classification of Landsat data.
Other patterns of landsurface-physical features are delineated by the visual interpretation of Landsat MSS and
TM imagery (1:100.000-1:25.000).
(3) After an insight and quantification is gained of the relation between the landsurface-physical variables
and the hydrological character of the Permo-Triassic-Liassic rocks, by comparison with hydrological field sur
vey data, surface water systems and related groundwater flow systems are identified.
(4) The spatial characteristics of the hydrological units are stored in a Geographic Information System,
which sërves as a data bank for semi-distributed water and sediment yield models.
(5) Landsat data can further be used to correlate reflectance indices with specific field-data-based model
This procedure is being developed for a reference area and will be tested for a control area during a later
stage of the investigation.
In conclusion, if one knows how to use remotely-sensed information, this data source could be an important
additional tool in solving the hydrological régionalisation problem.
1 INTRODUCTION curve Number Model (Soil Conservation
Service, 1972) cannot be applied to catchments
1.1 Problem-oriented régionalisation approach
with a complex spatial distribution of hydrologi
cal units. A more realistic way to deal with the
In Alpine environments, where a detailed gauging
network is often missing, reliable predictions of
stream runoff and sediment yield are most needed.
The extrapolation of records to ungauged catchments
can be performed by several régionalisation methods
(Figure 1). The choice for a specific approach de
pends on the nature of problems to be solved, the
scale at which a solution is required and the com
plexity of the research area (Simmers, 1984).
meters have no unique relation to field measure-
ments of hydrological phenomena or to landsurface-
physical variables, are not suited for the extrapo
lation of the results of gauged watersheds to un
problem of heterogeneity is to divide the catchment
into a number of homogeneous subareas and to model
the hydrological processes for each subarea separa
tely (semi-distributed models such as the USDAHL-74
Model;- Holtan et al., 1975).
Calibrated catchment models, in which the para-
regionalisation models
gauged watersheds. Consequently, in complex Alpine
regions, a physically-based model with a (semi)dis
tributed character is recommended.
[statistical models| [conceptual modelsj
1.2 Use of satellite imagery in catchment modelling
Figure 1. Régionalisation models.
Until now, the evaluation of the applicability of
remote sensing techniques to infer basic model para
meters has been focused on existing catchment models
(Peck et al., 1981; Engman, 1982; Rango, 1985). How
ever, these models do not have a significant poten
tial for using remotely-sensed information (Peck et
al, 1982).
Lumped models, such as the Stanford Watershed
Model IV (Crawford and Linsley, 1966) and the SCS
In (Alpine) regions, where a large number of factors
controls the hydrological regime, it seems to be
very difficult to predict the runoff of ungauged
catchments by purely statistical methods (Mosley,
1981; Ebisemiju, 1979). In such areas a conceptual
model is more appropriate, in which the types of
hydrological processes and their interrelationship
with landsurface-physical variables are considered.
The incorporation of Landsat data in catchment
response modelling has been described, among others,
by Ragan and Jackson (1980 : SCS Curve Number Model),
Groves and Ragan (1981 : Modified Stanford Watershed
Model) and Fisher and Ormsby (1982 : USDAHL-74
Model). As the Landsat bands can give only indirect
estimates of hydrological parameters, one has to
determine how landsurface-physical features are re
lated to hydrological characteristics of the area.
Field observations are indispensable for this pur
pose (Figure 2).