LASER ALTIMETRY FOR RIVER MANAGEMENT 
R. Brügelmann, A.E. Bollweg 
Ministry of Transport, Public Works and Water Management, Geo-information and ICT Department, 
P.O. Box 5023, 2600 GA Delft, The Netherlands 
r.brugelmann@agi.rws.minvenw.nl, a.e.bollweg@agi.rws.minvenw.nl 
Commission II, WG 11/3 
KEY WORDS: laser scanning, DEM/DTM, precision, hydrology, monitoring, vegetation classification 
ABSTRACT: 
Laser aitimetry seems to be an attractive method for the fast acquisition of up to date height data which can be useful for various river 
management tasks. The Geo-information and ICT department of the Ministry of Transport, Public Works and Water Management 
gathered many experiences in this field during the recent years. The topic of this paper is to give an overview of the use of laser 
altimetry for different river management applications. The first subject is floodplain vegetation classification for hydraulic modelling. 
Laser data adds useful structure information on spectral information for vegetation classification. Furthermore, the potential of laser 
altimetry for soil volume determination concerning costs and accuracy is discussed. Laser altimetry also offers new possibilities for 
monitoring of groynes and realistic visualizations of innovative river structures. In addition, the benefit of laser altimetry for the 
acquisition of detailed DEM's of the shallow parts of the riverbed in case of extreme low-water level is shown. Finally, laser 
altimetry has been investigated for measuring continuous water levels and wave characteristics such as amplitudes and wavelengths. 
1. INTRODUCTION 
One of the core tasks of the Dutch Ministry of transport, public 
works and water management (Rijkswaterstaat) is to guarantee 
citizens safety with regard to flooding and to enable and 
facilitate shipping along the great rivers. To fulfil these 
objectives a variety of underlying river management tasks has to 
be performed which requires different kinds of up to date geo- 
information. The demand for up to date geo-information is even 
expected to increase because of higher river discharges in the 
future due to climate change. In addition, a new concept of river 
management will be performed in The Netherlands: in the 
future both, the river and the vegetation in the riparian 
forelands, will be allowed to behave in a more natural and 
dynamic way as long as safety and shipping are not affected. 
For the regional departments of Rijkswaterstaat laser altimetry 
seems to be an attractive method for the fast acquisition of up to 
date height data. The role of the Geo-information and ICT 
Department is to advise the regional departments about such 
new techniques and the use of geo-information. The department 
is quite experienced with laser altimetry because of the co- 
ordination of the acquisition of the new country wide digital 
clevation model (AHN). which has been completed in 2003. 
Furthermore, the quality control of the laser altimetry data was 
done by the Geo-information and ICT Department. For this 
quality certification task a new height error description scheme 
was developed for DEM’s acquired by laser altimetry, allowing 
the quantification of error effects at different scales (Crombaghs 
et al., 2002). 
In the recent past a number of tailor made laser altimetry flights 
have been organized for specific water management objectives. 
The topic of this paper is to give an overview of the use of laser 
altimetry for various river management applications. Among 
them are: 
e Floodplain vegetation classification in combination with 
hyperspectral images for hydraulic modelling. 
eAcquisition of detailed and precise DEM's for soil 
volume determination concerning construction works 
in the floodplains. 
e Monitoring of groynes for maintenance and management 
tasks. 
* Acquisition of detailed DEM's of the shallow parts of the 
riverbed in case of extreme low water level. 
eContinuous water level determination along the river 
axis. 
e Wave amplitude and wavelength determination to verify 
ship wash modelling. 
Related work over river flood modelling with laser altimetry 
can be found in (Mandlburger and Brockmann, 2001), ( Cobby 
et al., 2001) and (Kraus, 2003). In the following paragraphs the 
above mentioned applications will be described in more detail. 
The required flight specifications and achieved accuracy will be 
discussed. 
2. FLOODPLAIN VEGETATION 
Floodplain vegetation influences the rivers discharge capacity 
in high water conditions through its hydraulic resistance (flow 
resistance). This is expressed by hydraulic roughness 
parameters which depends on many different factors like 
vegetation height, density, stem diameter and spatial patterns 
within vegetation among others (Asselman, 2001). The main 
input data for the hydraulic models for water level forecasting 
consist of these roughness parameters in combination with 
morphological data of riverbed and floodplains (see paragraph 
5). Both data have to be up to date. Therefore, mapping of the 
floodplain vegetation is crucial and has to be done regularly. 
There are different possibilities to gather the required 
vegetation roughness information of the floodplains. One 
possibility would be to directly derive the roughness informa- 
tion from laser altimetry data. Asselman did some investigations 
on this topic using (geo-)statistical characteristics of the data 
(see (Asselman, 2001) and (Asselman, 2002)) but concluded 
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