Riparian microtopography of Shonai River by applying pole-camera method Ryosuke AKAHORI (Aichi Institute of Technology) 8/11 7/29 1 2 3 4 A B C A B C A B C 08/30/2017 11/18/2016 07/29 and 08/11/2016 A B C 02/20/2018 A B C 02/13/2019 40m N 40m N 40m N 40m N 40m N gravel surface region flow vegetated region gravel surface region flow vegetated region gravel surface region flow vegetated region gravel surface region flow vegetated region calculation area total discharge 1/3 of the total vegetated region 75m³/s for the boundary gravel surface region Depth (m) Velocity (m/s) The hydraulic mechansims of transporting the fine sediment were then evaluated by calculating the local flow structures (The DSM obtained by the proposed method was used as the topographic data). Observation site The sandbars 28 km upstream from the mouth of the Shonai River in Japan (figure 4). The sandbar were excavated in 2012 to obtain a flat surface. Several flood events changed the landscape (figure 5). Figure 2. procedure of the “pole camera” method Figure 3. Example of the surfece of the DSM Pole-camera method The “pole-camera” method was oroginaly proposed in the field of the active fault research (Goto, 2015). ・The operator needs to rotate the pole and himself while the co-operator stands beside and captures images using a remote controller (Sony, RM-LVR2) (figure 2). ・The RTK-GNSS (Sokkia, GSX2) was used to obtain locations of the the ground control point (GCP). ・The SfM-MVS software (Agisoft, PhotoScan Professional edition, Ver. 1.2.6) was applied to obtain the digital surface model (DSM) and the ortho-images of the site (figure 3). The obtained DSM was used as the topographical data for the calculation. Numerical calculation procedure Discahrge: 75 m³/s in the secondary channel (representing the small flood discharge illustrated by magenta colored arrows in figure 5). Topography: the DSM previously obtained Model: the customized version of Nays 2D of iRIC 2.1 (https://i-ric.org/en/). (brief results are shown in figure 6) Remote controlled camera (Sony, QX-1) 7m telescopic pole (Promate，E-4867) Operators must rotate themselves while shoot- ing. It requres about 20 images for each standing location. In a single survey, it must be repeated in 20 to 30 locations. co-operator using a remote controller (Sony, RM-LVR2) The SfM-MVS (Agisoft, PhotoScan Professional edi- tion, Ver. 1.2.6) technique was applied to obtain the DSM and the ortho-images of the observation site. Field observation Figure 5. Ortho-rectified images of the site derived by the proposed "pole-camera" method (the calculation area and conditions are illustrated in the image on 07/29 and 08/11/2016.) Figure 1. The “pole camera” method The particle distributions (at sampling locations on figure 7) were classified into two groups (figure 8); one being the fine sediment group (green) and the other being the coarse material (magenta). Figure 7. Sediment sampling locations on the ortho-image (8/11/2016) Figure 8. Particle distributions Calculation results The ratio of u vegetation (estimated flow velocity in the vegetated area) to w s (1mm particle settling velocity) was evaluated (figure 9) based on the calculation results. The colored areas denote the regions where the 1mm particles (relatively fine) were transported as suspended sediment (and not trapped). Most of the magenta markers (locations covered by coarse materials) were located in the areas of the colored contours. Figure 9. Contour of the ratio of u vegetation to w s u vegetation /w s region 1: wake zone region 2: mixing-layer zone region 3: log-law zone u vegetation u vegetation =(2gI e /(C D a s )) 1/2 I e : the local energy slope that was inversely obtained by the calculated result C D : the drag coefficient (C D = 1.0) a s : the degree of vegetated density (a s = nd/s 2 ) n: the number of vegetation d: its diameter s: the side length of an observed area) Figure 6. Calculated depth and velocity Conclusions ・An alternative method to capture images for the SfM-MVS was proposed. ・The DSM was applied to a numerical calculation reproducing the flow structures. ・The estimated regions (without fine sediment deposits) were relatively consistent with the location where coarse materials were sampled on their surface. Purpose This study proposed an alternative method (figure1) to capture images for the SfM-MVS. ACKNOWLEDGMENTS: This work was supported by JSPS KAKENHI Grant Number JP19K04625. REFERENCES: Goto, H. (2015). Mapping of Fault Geomorphology Using "Structure from Motion - Multi - Video Stereo" Photogrammetry with Old / Hi-view Aerial Photography, Active Fault Research, No. 42, pp. 73-83. (in Japanese) Harada, M., Nagayama, S., Oishi, T., and Kayaba, Y. (2015). Microtopography formation after flood-channel excavation ㏌ Ibi-River, Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), Vol. 71 (2015), No. 4, pp. I_1171-I_1176. (in Japanese) Background Excessive overgrowth of the riparian vegetation in Japan The early stage of the overgrowth is produced by the entrapment of the fine materials by the pioneering plant (Harada, et al., 2015). The UAV and the SfM-MVS They are widely used to study the micro-scale topography and the riparian vegetation. However, restricted areas for UAV are expected to expand. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 0.001 0.01 0.1 1.0 10.0 100.0 d002 d003 d004 d005 d006 d008 d009 d010 d011 d019 d020 d007 d012 d013 d014 d015 d016 d017 d018 diameter (mm) cumulative percent passing Figure 4. Observation site of the study: 28 km upstream from the mouth of the Shonai River Flow Flow Gravel surface region upstream of the bar (maintained by the deposition of the gravel materials during flood events) Overgrown vegetational surface region downstream of the bar (not intensively disturbed throughout the flood events and the relatively fine materials had been trapped) a) b) a) b) Nagoya Nisshin Owari Asahi Kasugai Miyoshi Toyoake Inazawa 28km from the river mouth, Observatioin Site The Shonai River Esri, HERE, DeLorme, MapmyIndia, © OpenStreetMap contributors, and the GIS user comunity km Tokyo Osaka Nagoya gravel surface region vegetated region
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Riparian microtopography of Shonai River by applying pole-camera methodRyosuke AKAHORI (Aichi Institute of Technology)
8/117/29
40m
1
2
3
4
A B C A B C A B C
08/30/2017
40m
11/18/201607/29 and 08/11/2016
40m
A B C
02/20/2018
A B C
02/13/2019
40mN
40mN
40mN
40mN
40mN
gravel surface region
flow
vegetated region
gravel surface region
flow
vegetated region
gravel surface region
flow
vegetated region
gravel surface region
flow
vegetated region
calculationarea
total discharge
1/3 of the total vegetatedregion
75m³/s
for the boundary
gravel surface region
Depth (m) Velocity (m/s)
The hydraulic mechansims
of transporting the f ine
s e d i m e n t w e r e t h e n
evaluated by calculating
the local flow structures
(The DSM obtained by the
proposed method was
used as the topographic
data).
Observation site
The sandbars 28 km upstream from the mouth of the Shonai River in
Japan (figure 4). The sandbar were excavated in 2012 to obtain a flat
surface. Several flood events changed the landscape (figure 5).
Figure 2. procedure of the “pole
camera” methodFigure 3. Example of the surfece of the DSM
Pole-camera method
The “pole-camera” method was oroginaly proposed in the
field of the active fault research (Goto, 2015). ・The operator needs to rotate the pole and himself while the co-operator stands
beside and captures images using a remote controller (Sony, RM-LVR2) (figure 2).
・The RTK-GNSS (Sokkia, GSX2) was used to obtain locations of the the ground
control point (GCP).
・The SfM-MVS software (Agisoft, PhotoScan Professional edition, Ver. 1.2.6) was
applied to obtain the digital surface model (DSM) and the ortho-images of the site
(figure 3). The obtained DSM was used as the topographical data for the calculation.
Numerical calculation procedureDiscahrge: 75 m³/s in the secondary channel
(representing the small flood discharge illustrated
by magenta colored arrows in figure 5).
Topography: the DSM previously obtained
Model: the customized version of Nays 2D of iRIC
2.1 (https://i-ric.org/en/).
(brief results are shown in figure 6)
Remote controlled camera (Sony, QX-1)
7m telescopic pole(Promate，E-4867)Operators must rotate
themselves while shoot-ing.It requres about 20 images for each standing location.In a single survey, it must be repeated in 20 to 30 locations.
co-operator using a remote controller (Sony, RM-LVR2) The SfM-MVS (Agisoft, PhotoScan Professional edi-
tion, Ver. 1.2.6) technique was applied to obtain the DSM and the ortho-images of the observation site.
Field observation
Figure 5. Ortho-rectified images of the site derived by the proposed "pole-camera" method
(the calculation area and conditions are illustrated in the image on 07/29 and 08/11/2016.)
Figure 1. The “pole camera” method
The particle distributions (at
sampling locations on figure 7)
were classified into two groups
(figure 8); one being the fine
sediment group (green) and
the other being the coarse
material (magenta).
Figure 7. Sediment sampling locations
on the ortho-image (8/11/2016) Figure 8. Particle distributions
Calculation results
The rat io of uv e g e t a t i o n
(estimated flow velocity
in the vegetated area) to
ws (1mm particle settling
velocity) was evaluated
(figure 9) based on the
calculation results. The colored areas denote the
regions where the 1mm particles
(relatively fine) were transported
as suspended sediment (and not
trapped). Most of the magenta
markers (locations covered by
coarse materials) were located in
the areas of the colored contours. Figure 9. Contour of the ratio of uvegetation to ws
uvegetation/ws
region 1: wake zone
region 2:mixing-layer zone
region 3: log-law zone
uvegetation
uvegetation=(2gIe/(CDas))1/2
Ie: the local energy slope that was inversely obtained by the calculated resultCD: the drag coefficient (CD = 1.0)as: the degree of vegetated density (as = nd/s2) n: the number of vegetationd: its diameters: the side length of an observed area)
Figure 6. Calculated depth and velocity
Conclusions・An alternative method to capture images for the SfM-MVS was proposed.
・The DSM was applied to a numerical calculation reproducing the flow structures.
・The estimated regions (without fine sediment deposits) were relatively consistent
with the location where coarse materials were sampled on their surface.
Purpose
This study proposed
a n a l t e r n a t i v e
method (figure1) to
capture images for
the SfM-MVS.
ACKNOWLEDGMENTS: This work was supported by JSPS KAKENHI Grant Number JP19K04625.
REFERENCES: Goto, H. (2015). Mapping of Fault Geomorphology Using "Structure from Motion - Multi - Video Stereo" Photogrammetry with Old / Hi-view Aerial
Photography, Active Fault Research, No. 42, pp. 73-83. (in Japanese)
Harada, M., Nagayama, S., Oishi, T., and Kayaba, Y. (2015). Microtopography formation after flood-channel excavation ㏌ Ibi-River, Journal of Japan Society of
Civil Engineers Ser. B1 (Hydraulic Engineering), Vol. 71 (2015), No. 4, pp. I_1171-I_1176. (in Japanese)
Background
Excessive overgrowth of the
riparian vegetation in Japan
The ea r l y s tage o f t he
overgrowth is produced by
the entrapment of the fine
materials by the pioneering
plant (Harada, et al., 2015).
The UAV and the SfM-MVS
They are widely used to
s t u d y t h e m i c r o - s c a l e
topography and the riparian
v e g e t a t i o n . H o w e v e r ,
restricted areas for UAV are
expected to expand.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.001 0.01 0.1 1.0 10.0 100.0
d002d003d004d005d006d008d009d010d011d019d020d007d012d013d014d015d016d017d018
diameter (mm)
cum
ulat
ive
perc
ent p
assi
ng
Figure 4. Observation site of the study: 28 km upstream from the mouth of the Shonai River
Flow
Flow
Gravel surface region upstream of
t h e b a r ( m a i n t a i n e d b y t h e
deposition of the gravel materials
during flood events)
Overgrown vegetational surface
region downstream of the bar (not
intensively disturbed throughout
the flood events and the relatively
fine materials had been trapped)
a)
b)
a)
b)Nagoya
Nisshin
Owari Asahi
Kasugai
Miyoshi
Toyoake
Inazawa28km from the river mouth,Observatioin Site
The Shonai River
Esri, HERE, DeLorme, MapmyIndia, © OpenStreetMapcontributors, and the GIS user comunity km
Tokyo
Osaka
Nagoya
gravel surface region
vegetated region
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