Method Development for Remote Sensing of River Flow with Limited
Ground-Based Measurements
Abstract
Quantification of river flow is a significant component of water
resource management needed to develop infrastructure, prepare for
drought or flood, and ensure equitable resource use. Yet, these data
have often been deficient in rural regions generally dependent on
smaller river systems, especially in low- and middle- income countries,
and in places where no remote gaging capabilities currently exist. A
relationship between river flow and width has been previously
demonstrated in attempts to record and monitor flow with only
satellite-based measurements; however, those methods have focused on
rivers with a width of > 30m and have shown extreme errors
when compared to historical gaging records. A new technique for
monitoring river flow remotely is presented here, which uses Manning’s
equation for open channel flow coupled with width measurements from
satellites. This technique allows for the creation of a remotely-sensed
historical river flow record and uses the minimum number of ground-based
measurements for the calibration of Manning’s equation. Cross-river
depth profile, discharge, and slope are necessary for initial
calibration. This method used four-band satellite images with
3m-resolution for width measurements, with images being adjusted for the
Normalized Difference Water Index (NDWI) for better delineation of the
water’s edge. Buffalo Creek, in Freeport, Pennsylvania and the Mutale
River, in the Limpopo Province of South Africa, were used as study
locations. An estimation of flow at each site was obtained using every
available satellite image of those transects. Preliminary results
indicated successful calibration of Manning’s equation for the
individual river transects, and verification of this method yielded flow
estimation with an average of 74% error at Buffalo Creek and 48% error
at the Mutale River, when compared to historical data from gages present
near the study sites. The primary challenge of using this method on
smaller rivers is the determination of width from the satellite images.
Automated techniques to delineate the water’s edge are presented as
recommendations to increase accuracy. This method may be used as an
additional tool in river flow monitoring for water resource management.