river morphology monitoring using multitemporal sar data preliminary results

AbstractIn this paper, we test the capability of satellite synthetic aperture radar (SAR) images to enhance the monitoring of river geomorphological processes. The proposed approach exploits the recently introduced Level-α products. These products are bi-temporal RGB composites in which the association color-object, being physical-based, is stable whatever the scene is considered. This favors the detection of temporary rivers' characteristics for classification purposes in a change-detection environment. The case study was implemented on the Orco river (northwest Italy), where a set of 39 COSMO-SkyMed SAR stripmap images acquired from October 2008 to November 2014 was used to monitor channel planform changes. This preliminary study is devoted to assess the suitability of Level-α images for geomorphologist, with particular reference to the detection of phenomena of interest in river monitoring. This is prior for semi-automatic or automatic classification activities

Hydrological modeling in ungauged basins using SAR data

In this paper we propose a methodology devoted to exploit high resolution radars for monitoring water bodies in semi-arid countries. The proposed approach is based on appropriate registration, calibration and processing of SAR data, producing information ready to use by end-users. The obtained results were used to (i) estimate a relationship between surface and volume of water stored in reservoirs and (ii) validate a hydrological model that simulates the time evolution of water availability

Modeling Watershed Response in Semiarid Regions With High-Resolution Synthetic Aperture Radars

In this paper, we propose a methodology devoted to exploit the outstanding characteristics of COSMO-SkyMed for monitoring water bodies in semiarid countries at a scale never experienced before. The proposed approach, based on appropriate registration, calibration, and processing of synthetic aperture radar (SAR) data, allows outperforming the previously available methods for monitoring small reservoirs, mainly carried out with optical data, and severely limited by the presence of cloud coverage, which is a frequent condition in wet season. A tool has been developed for computing the water volumes retained in small reservoirs based on SAR-derived digital elevation model. These data have been used to derive a relationship between storage volumes and surface areas that can be used when bathymetric information is unavailable. Due to the lack of direct measures of river's discharge, the time evolution of water volumes retained at reservoirs has been used to validate a simple rainfall-runoff hydrological model that can provide useful recommendation for the management of small reservoirs. Operational scenarios concerning the improvement in the efficiency of reservoirs management and the estimation of their impact on downstream area point out the applicative outcomes of the proposed method

Potential and limitations of high resolution multitemporal sar images in river morphology

In this study we test the capability of satellite synthetic aperture radar (SAR) images to enrich the monitoring of river geomorphological processes. A case study on the Italian River Orco is presented; a set of 100 COSMOSkyMed stripmap images (from October 2008 to December 2016) from Italian Space Agency was employed. All the data, acquired with medium look angle (almost 30◦) and HH polarization for increasing the land-water contrast, were processed in order to calibrate, register and reduce the speckle effect. Moreover, the optimal weighting multi-temporal De Grandi filter was adopted to allow an effective extraction of the water surfaces contour. This method was applied to extract water contours over the entire historical series of SAR datasets available. Thanks to the generated information we were able to monitor the lateral dynamic of the water channels and infer on the relations between low or peak flow and river morphology. Multi-temporal SAR images were compared to orthophotos and in situ measurements (performed at the same time of a SAR acquisition) in terms of river features extraction (e.g. active channel, vegetated islands) and measurements of morphometric parameters (e.g. reach length, channel width, curvature and sinuosity). Results of this comparison highlighted the potential offered by the use of SAR technology, with some limitations. In particular, good performances were reached by the extraction of the active channel and vegetated island compared to the ones obtained using the orthophotos. On the other hand, some issues were encountered in extracting water surfaces where riffles exhibit surface waves having heights greater than the wavelength of the electromagnetic signal of SAR, which causes a low land-water contrast. Hence, given the high spatial (3 m) and temporal resolution (15 days) of SAR images and the all-weather all-time acquisition conditions, a significant enhancement in the river management capabilities is possible, in particular regarding the assessment of hydro-morphological river quality, as strongly suggested by European Commission’s Water Framework Directive (2000/60/EC

Advanced Technologies for Satellite Monitoring of Water Resources

Exploitation of synthetic aperture radar satellite data. Monitoring of surface water resources with high resolution in time and space. Low-cost technic for freshwater monitoring. Appropriate technology for developing countries. Retrieval of river features: active channels, sediment bars and wet channels

SAR remote sensing of river morphodynamic on a monthly basis

Satellite remote sensed data provide the opportunity of observing rivers with high resolution in space and time and covering wide areas. For this reason, such data have been widely used to monitor river morphological changes in time (Marcus and Fonstad, 2010). In this study we propose the exploitation of satellite synthetic aperture radar (SAR) data. Although SAR data have been so far poorly used for river observation they have significant advantages over more widely used data such as for example optical one: cloud cover do not influence earth surface observation, the spatial resolution is very high (up to 1m) and the time resolution is also very high (about 15 days). In this study we retrieved from a multitemporal SAR dataset the surface covered by water, we tested the results against orthophotos and in situ measurements and observed the river morphological change in a time interval of 8 years with an average frequency of about one month

Utilizzo di sati satellitari di tipo SAR per il monitoraggio dei corsi d'acqua

Nel presente lavoro proponiamo lo sfruttamento di dati satellitari di tipo radar ad apertura sintetica (SAR) per il monitoraggio dell’evoluzione morfologica dei corsi d’acqua. Sebbene i dati SAR siano stati finora poco utilizzati per l'osservazione dei corsi d’acqua, presentano vantaggi significativi rispetto a dati più ampiamente utilizzati come ad esempio i dati ottici: la copertura nuvolosa non influenza l'osservazione della superficie terrestre, la risoluzione è molto alta (fino a 1 m) con acquisizioni ogni 7 giorni in media