The Monitoring of River Flows and the Management of Flood Hazards using UAVs

Abstract:

The increasing occurrence of extreme precipitation events as well as severe droughts, coupled with greater and greater human occupation of flood plains, makes increased monitoring of flows in rivers an important component of assessing the potential for water-related natural disasters as well as responding to them when they do occur. Unfortunately, this increasing need comes at a time when funding for monitoring activities is generally decreasing. In the United States, for example, gauging stations with daily flow records going back several decades or even a hundred years have been abandoned, and new stations in critical areas have not even been established. A methodology based on periodic UAV-based imaging of an entire river offers the prospect of obtaining inexpensive, real-time, high-resolution data for the determination of the river flows. The method makes use of fact that as the flow in a river rises or falls, the areal extent covered by the river changes accordingly. Furthermore, barring anthropogenic changes, the area inundated by a flow of a particular magnitude is invariant in time. For a given stretch of a river, a sequence of images spanning the full range of flow conditions provides the basic template for determining river flows. The actual flow in the river can be calibrated using previously measured flow data corresponding the dates of old aerial or satellite imagery, or calculated from new imagery by using standard flow equations and the topography of the banks of the river, determined by field surveying or Lidar. Once the basic template has been established, determination of “the state-of-the-river” at any point in time can be obtained by comparing newly-acquired UAV images with those in the database. And because a given image encompasses many topographic features that are inundated to differing extents, the resolution of the flow determination is limited only by the completeness of the imagery in the basic template. Repeat flights at weekly intervals can be used to monitor the river under normal flow conditions while daily or even hourly flights can be used to track the rise and fall of a particular flood event.