TY - JOUR

T1 - Comparing the accuracy of several field methods for measuring gully erosion

AU - Castillo, Carlos

AU - Pérez, Rafael

AU - James, Michael

AU - Quinton, John

AU - Taguas, Encarnación V.

AU - Gómez, José A.

PY - 2012/7

Y1 - 2012/7

N2 - Most fi eld erosion studies in agricultural areas provide little information onthe probable errors involved. Here, for the fi rst time, we compare the accuracy,time and cost of conventional and new methodologies for gully surveying,and provide a model to estimate the effort required to achieve a specifi edaccuracy. Using a terrestrial LiDAR survey of a 7.1-m-long gully reach as abenchmark data set, the accuracies of different measurement methods (anew 3D photo-reconstruction technique, total station, laser profi lemeter,and pole) are assessed for estimating gully erosion at a reach scale. Basedon further fi eld measurements performed over nine gullies (>100 m long), asimulation approach is derived to model the expected volume errors when2D methods are used at the gully scale. All gullies considered were locatednear Cordoba, Spain. At the reach scale, the fi eld measurements using 3Dphoto-reconstruction and total station techniques produced cross-sectionalarea error values smaller than 4%, with other 2D methods exceeding 10%.For volume estimation, photo-reconstruction proved similar to LiDAR data,but 2D methods generated large negative volume error (EV) values (<–13%for laser profi lemeter and pole). We show that the proposed error expressionsderived from the model are in line with the reach-scale fi eld results. A measurement distance factor (MDF) is defi ned that represents the ratio betweencross-section distance and the gully length, and thus refl ects relative surveyeffort. We calculate the required MDF for specifi ed values of EV, illustratinghow MDF decreases with increasing gully length and sinuosity.

AB - Most fi eld erosion studies in agricultural areas provide little information onthe probable errors involved. Here, for the fi rst time, we compare the accuracy,time and cost of conventional and new methodologies for gully surveying,and provide a model to estimate the effort required to achieve a specifi edaccuracy. Using a terrestrial LiDAR survey of a 7.1-m-long gully reach as abenchmark data set, the accuracies of different measurement methods (anew 3D photo-reconstruction technique, total station, laser profi lemeter,and pole) are assessed for estimating gully erosion at a reach scale. Basedon further fi eld measurements performed over nine gullies (>100 m long), asimulation approach is derived to model the expected volume errors when2D methods are used at the gully scale. All gullies considered were locatednear Cordoba, Spain. At the reach scale, the fi eld measurements using 3Dphoto-reconstruction and total station techniques produced cross-sectionalarea error values smaller than 4%, with other 2D methods exceeding 10%.For volume estimation, photo-reconstruction proved similar to LiDAR data,but 2D methods generated large negative volume error (EV) values (<–13%for laser profi lemeter and pole). We show that the proposed error expressionsderived from the model are in line with the reach-scale fi eld results. A measurement distance factor (MDF) is defi ned that represents the ratio betweencross-section distance and the gully length, and thus refl ects relative surveyeffort. We calculate the required MDF for specifi ed values of EV, illustratinghow MDF decreases with increasing gully length and sinuosity.

KW - Soil erosion

KW - SfM-MVS

U2 - 10.2136/sssaj2011.0390

DO - 10.2136/sssaj2011.0390

M3 - Journal article

VL - 76

SP - 1319

EP - 1332

JO - Soil Science Society of America Journal

JF - Soil Science Society of America Journal

SN - 0361-5995

ER -