Estimating River Discharges in Ungauged Catchments Using the Slope–Area Method and Unmanned Aerial Vehicle

Abstract

River discharge is of great significance in the development of water resources and ecological protection. There are several large ungauged catchments around the word still lacking sufficient hydrological data. Obtaining accurate hydrological information from these areas is an important scientific issue. New data and methods must be used to address this issue. In this study, a new method that couples unmanned aerial vehicle (UAV) data with the classical slope–area method is developed to calculate river discharges in typical ungauged catchments. UAV data is used to obtain topographic information of the river channels. In situ experiments are carried out to validate the river data. Based on slope–area method, namely the Manning–Strickler formula (M–S), Saint-Venant system of equivalence (which has two definitions, S-V-1 and S-V-2), and the Darcy–Weisbach equivalence (D–W) are used to estimate river discharge in ten sections of the Tibet Plateau and Dzungaria Basin. Results show that the overall qualification rate of the calculated discharge is 70% and the average Nash–Sutcliffe efficiency coefficient is 0.97, indicating strong practical application in the study area. When the discharge is less than 10 m3⁄s, D–W is the most appropriate method; M–S and S-V-1 are better than other methods when the discharge is between 10 m3⁄s and 50 m3⁄s. However, if the discharge is greater than 50 m3⁄s, S-V-2 provides the most accurate results. Furthermore, we found that hydraulic radius is an important parameter in the slope–area method. This study offers a quick and convenient solution to extract hydrological information in ungauged catchments.

Evaluation of Flow Resistance Models Based on Field Experiments in a Partly Vegetated Reclamation Channel

“…Our results are in agreement with Yang et al [28], who achieved a minimum prediction error (indicated in their work as relative accuracy) equal to 9.14%, computed by comparing the global flow resistances based on field measurements with those retrieved by employing a model based on unmanned aerial vehicles (UAV) techniques, in a river partially covered by emergent riparian vegetation. This is a promising finding since it demonstrates that the application of a simple methodology, like DCM [11] combined with one of the four examined composite cross section methods [12][13][14][15], can lead to results comparable with those obtained by using more complex models.…”

Applications of Unmanned Aerial Systems (UASs) in Hydrology: A Review

“…Yang et al [82] calculated the river discharge in ten sections in the Tibetan Plateau and Province of Xinjiang by (i) retrieving the parameters of the slope-area method using an UAS to generate a digital orthophoto map and a DSM and (ii) applying three different formulas (Manning-Strickler, Saint-Venant and Darcy-Weisbach). In Yang et al [83], UAS remote sensing, high altitude remote sensing and in situ measurements are combined to estimate river flow in medium/small wide shallow rivers in arid areas. The attenuation coefficient and discharge of the ungauged Hotan river (Central Asia) was calculated by applying energy equations and a trapezoidal cross-section discharge equation.…”

Simulation of Lake Water Volume in Ungauged Terminal Lake Basin Based on Multi-Source Remote Sensing

“…Riggs proposed the slope-area method (SAM), a classic hydraulic equation to calculate the runoff by using the slope and river cross-sectional area [38], that is based on physical laws and mathematical derivation and widely used for calculating the discharge of small-and medium-sized rivers [39,40]. We used three-dimensional surface data obtained from UAV-based remote sensing to calculate the river flow [41] with the SAM [42,43]. The equations used for the SAM calculation are as follows:…”

“…where v is the average flow, m/s; k is the conversion factor, m 1/3 /s (=1); n is the empirical roughness coefficient; the hydraulic radius R is the ratio of the river section area A to the wet cycle L; J is the hydraulic gradient of the river channel; and Q is the river flow, m 3 /s. The R and J values were obtained from UAV-based remote sensing [42,43].…”