We thank all the participants. The playpark events were supported by Ube city and Kuroishi, Kotosaki, Kiwanami, and Kamiube towns and schools along with Yamaguchi University.

This study protocol was approved by the Yamaguchi University Review Committee for Non-Medical Research Involving Human Participants. See Table of Materials for a list of all materials, equipment, and software used in this protocol. Public announcements were made regarding the date, time, and location that children, along with their parent(s) or guardian(s), could gather to voluntarily collaborate to create, use, and then clean up a playpark in an environment designed to encourage their creativity.
1. Park landscapes and resources
<ol>
	<li>Conduct on-site surveys of the topography and resources of each park and specifically design the waterslides for each park to utilize the specific resources available. If possible, place the waterslides in an open area so they are visible from all directions to attract visitors to the playground. 
	NOTE: Figure 1 shows the Google Maps aerial view of each park, indicating the location and direction of the waterslide (WS).</li>
	<li>Design and build waterslides based on the existing terrain. 
	NOTE: The slope and length of each waterslide is shown in Table 1.
	<ol>
		<li>To make a waterslide for a flat park (Park 1, WS1; Video 1):
		<ol>
			<li>Design a tower structure using scaffolding pipes and clamps to allow for easy assembly of a strong but temporary structure (Figure 2Ab).</li>
			<li>Build the frame for the pool section of the waterslide from 3 m long bamboo rods (Figure 2Aa1). Ensure the waterslide (Figure 2Aa2) has an angle of 25&#176;, a length of 1.8 m, and includes a pool at the bottom. 
			NOTE: Kuroishi Park is flat (Figure 2A).</li>
		</ol>
		</li>
		<li>To make a waterslide for a hilly park (Park 2, WS2; Video 2), take advantage of the natural slope.
		<ol>
			<li>As in step 1.2.1, construct a frame for the pool section from bamboo rods and plywood using regional resources (Figure 2B). Ensure that the waterslide has an angle of 30&#176;, a length of 6 m, and includes a pool at the bottom. 
			NOTE: Kotosaki Park is hilly (Figure 1B).</li>
		</ol>
		</li>
		<li>If a park has a small slope in its center (Park 3, WS3; Video 3), create the waterslide using this small slope.
		<ol>
			<li>Use bamboo rods and scaffolding to increase the natural slope (Figure 2C) upon which to build a waterslide, as in step 1.2.1. Ensure that the waterslide has an angle of 21&#176; at its steepest, a length of 4 m, and includes a pool at the bottom. 
			NOTE: Kiwanami Park has small slope in its center (Figure 1C).</li>
		</ol>
		</li>
		<li>If present, use stairs to create a waterslide (School 4, WS4; Video 4).
		<ol>
			<li>To cover the staircase, build a structure with plywood and square wooden rods (Supplemental File 1) covered with cardboard to form a rail to keep the children on the slide (Figure 2D, center drawing). Ensure that the waterslide has an angle of 27&#176; and length of 6 m. 
			NOTE: Kamiube elementary school has a staircase in the schoolyard (Figure 1D).</li>
		</ol>
		</li>
		<li>Consider the safety of the playparks (Supplemental File 1).
		<ol>
			<li>To verify the safety of the structures, calculate the strength using simulations such as Finite Element Methods (FEM) (e.g., Adobe Fusion 360; Supplemental File 1).</li>
			<li>Make a prototype. Have multiple people pilot the prototype to find any potential risks, such as hard/protruding parts. If found, eliminate or cover such parts with soft caps. Consider leaving some minimal risks to allow children to learn how to overcome the risks on their own (Supplemental File 1).</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Cover the slope with a tarp to create a waterslide and pool area (Supplemental File 1).</li>
	<li>Supply water to the waterslide via a hose from the park water supply.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64235/64235fig01.jpg" /> 
Figure 1: Park landscapes on Google maps. (A) WS1 at Park 1: Kuroishi. (B) WS2 at Park 2: Kotosaki. (C) WS3 at Park 3: Kiwanami. (D) WS4 at Elementary School 4: Kamiube. Scale bars = 20 m (A-D). Abbreviation: WS = waterslide. <a href="https://www.jove.com/files/ftp_upload/64235/64235fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Assembling materials (see Table of Materials)
<ol>
	<li>Smooth and clean the material surface.</li>
	<li>Assemble the framework with pipes, boards, joints, screws, and ropes, using an impact driver and a saw (Supplemental File 1).</li>
	<li>Stake the corners of the framework into the ground.</li>
	<li>Fix cardboard cushions at the steps.</li>
	<li>Cover with the tarp to fit the shapes and secure with stakes and waterproof tape (Supplemental File 1).</li>
	<li>Run hose water down from the slide top.</li>
	<li>Check the safety repeatedly and reinforce as needed.</li>
	<li>Continually monitor the safety during use and repair any issues immediately.</li>
</ol>
3. Recording and quantitative analyses of activity
<ol>
	<li>Capture the children&#39;s use of the slides using video cameras.</li>
	<li>Estimate the ages of the children using each waterslide based on their height (Table 2).</li>
	<li>Assess the relationships between flow lines and activity level through qualitative observations and quantitative analyses, as shown in Figure 3.
	<ol>
		<li>Convert video data to JPEG image files per second using Python (Supplemental File 2).</li>
		<li>Use Keynote to track each child&#39;s location with respect to the waterslide. Manually transform the location information to the top view image of the waterslide design (Supplemental File 2).</li>
		<li>Convert screenshots of a series of the object tracks to MP4 files (Supplemental File 2).</li>
		<li>Use Python detection on the MP4 files to determine object coordinates (Supplemental File 2) and calculate velocity (Supplemental File 2).</li>
		<li>Perform one-way ANOVA to determine the child motion [m/s] differences in WS1-4 against one another (put * if the p-value is &#60;0.05).</li>
	</ol>
	</li>
</ol>

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The authors declare no conflicts of interest associated with this manuscript.

These waterslides were set up with the goal of encouraging children to spontaneously gather in a city park and interact with one another and the natural environment. We emphasized the collaborative creative processes in which children, adults, students, and citizens worked together to design, build, and clean up the waterslides. All enjoyed working together to overcome the challenges11,12. Animal models have shown that deficits in this type of critical period learning experience13,14 may affect future social adaptability and psycho-emotional function2,15,16.
To create the waterslides, a ground slope (WS2, WS3) or stairs (WS4) were used. If there was no slope, a simple temporary slope was created by building a platform from boards and a single-pipe scaffold (WS1). Bamboo, a readily available regional resource17, was used for the waterslide frameworks in Parks 1-3. Bamboo grows quickly and must be controlled to prevent overgrowth, making its use in this application ideal18.
Regarding WS1, before confirming the motion tracking lines (Figure 5A), we had expected that the whole framework (Figure 2Aa1,a2,b) would be included in the waterslide structure. However, the motion tracking analysis revealed a clear division into two different substructure lines. Consequently, after this first trial and analysis of WS1, we simplified the waterslide design by removing the additional tower. Thus, the tower of WS1 (Figure 2Ab) was removed from the quantitative analysis.
All four types of slides attracted children to gather spontaneously. Activity at WS4 was higher than at the other slides, potentially because, based on our estimates (Table 2), the children using WS4 were older than at the other waterslides and therefore likely had more developed personalities. This could translate to children with more advanced social skills, construction ideas, and collaborative abilities. The activity difference could also be caused by the different waterslide designs; unlike the other slides that had a pool at the bottom where children could stay after sliding down, WS4 had no pool but side stairs that allowed the children to easily climb up again after sliding down, perhaps encouraging the simpler repetitive behavior. The location of the waterslide may also have been responsible for the higher activity at WS4. WS1-3 were at local parks, while WS4 was in a schoolyard, where it is reasonable to assume that the students were able to relax and play in their familiar surroundings. If educational and socioeconomic surveys could be collected for individuals using this equipment, the combination of information could provide insight into the children&#39;s neuropsychological development. In addition, the potential impact of COVID-19 must also be considered. Activity at WS4 was assessed in 2021, a time of ongoing COVID-related restrictions, whereas activity at WS1-3 took place prior to the pandemic. The activity level at WS4 could represent a response to the long period of reduced social play opportunities19. Due to the limitations inherent in these single observation events, further detailed studies including individual personal surveys are required.
To determine the mechanical safety of the framework designs20,21, a finite element simulation analysis22 was performed using Adobe Fusion (free version)23 for the bending of the plywood on the auxiliary support frame in the slide section. The auxiliary structure was designed to withstand a weight of 100 kg, assuming that four children weighing 25 kg each would use the slide at the same time (not shown). All the waterslides were successfully used by the children with no serious accidents. The tarp slipped down slightly and was corrected a few times. Only one incident was observed; this case involved a first-grade boy diagnosed with autism7,24. At first, the child seemed scared, but after watching the other children, he too wanted to join. The boy approached timidly and began to slide down slowly. After a few attempts, he slipped, fell, and hit his mouth on the slide surface. He suffered a small cut on the inside of his mouth. After this experience, he returned to his mother. We were concerned that this might be a negative experience for him. However, he subsequently participated in playpark events with great excitement and increased risk taking.

Increased urbanization has led to decreased opportunities for children to explore the natural outdoor environment. In particular, due in part to the declining birthrate and increasing prevalence of small nuclear families, Japanese children are losing opportunities to learn experientially about diversified social structures1. The Ministry of Education, Culture, Sports, Science and Technology of Japan has reported an increasing number of elementary school students with developmental disabilities and associated social disability, although a causal relationship has been not demonstrated2,3. Moreover, an Organization for Economic Co-operation and Development (OECD) survey found that Japanese children in junior high school interact with social media more frequently than children in other countries, despite the fact that many families do not allow their children access to smartphones at an early age4. As parents have become more educationally oriented, children are no longer playing outside in high-risk activities and are spending more time indoors under the watchful eye of adults5. However, outside the home, which is diverse and full of unknowns and potential threats, is often the best educational environment in which children can learn and grow while finding their own challenges and learning to overcome difficulties by working together with friends6. 
To encourage outdoor play, we held playpark events to afford children the opportunity to voluntarily experience nature through play and to socially interact and share challenges with friends and others7. The playpark is a special section in a city park where children can experience a variety of outdoor activities such as climbing trees, building playground equipment out of natural materials, and learning to build and manage a fire8. In a collaborative project to create a playpark in Ube City, Yamaguchi Prefecture, Japan, during 2018-2019, we explored how citizens could proactively create a nature-based experience for children. We set the following goals: (i) to facilitate social interaction by encouraging children to gather spontaneously, and (ii) to create an environment full of creative opportunity by utilizing natural resources such as the sky, soil, water, and trees9,10, and clean up the environment by using scrap cardboard. The events were scheduled to take place in four urban towns during the summer and fall. Given that most children instinctively love to play in water, we designed four waterslides that would take advantage of the regional resources. This report describes the results of Yamaguchi University's Ube City 2019 collaborative project "Play Leader Training Course", which was created through cooperation between the university and local citizens. Three events were completed in 2019; the fourth event occurred in 2021 during the period when COVID-19 was interfering with child socialization. The date and time of the playpark events is shown in Table 1. "Time" is the duration of the event and "Max time" is the 1 min period at each event that was quantitatively analyzed (the most active 1 min). This paper presents the four designs used, their implementation, and a quantitative evaluation of how the children interacted with the waterslides and each other during our observations.

<table><tbody><tr><td>&lt;strong&gt;WS1&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>pipes (6)</td><td></td><td></td><td>NFG Ecostar 700N &amp;Phi;48.6 mm x 0.9 m</td></tr><tr><td>pipes (27)</td><td></td><td></td><td>NFG Ecostar 700N &amp;Phi;48.6 mm x 1.8 m</td></tr><tr><td>pipes (2)</td><td></td><td></td><td>NFG Ecostar 700N &amp;Phi;48.6 mm x 2.4 m</td></tr><tr><td>cover (35)</td><td></td><td></td><td>for &amp;Phi;48.6 mm</td></tr><tr><td>&amp;nbsp;joint (36)</td><td></td><td></td><td>for&amp;nbsp; &amp;Phi;48.6 mm</td></tr><tr><td>Plywood boards (2)</td><td></td><td></td><td>13 x 900 x 1800 mm</td></tr><tr><td>&amp;nbsp;tarp (blue) (1)</td><td></td><td></td><td>0.25 x 4500 x 4500 mm</td></tr><tr><td>bamboo rod (8)</td><td></td><td></td><td>15 mm x 2000 mm</td></tr><tr><td>rope (1)</td><td></td><td></td><td>&amp;Phi;18 mm x 200 m</td></tr><tr><td>PP rope (1)</td><td></td><td></td><td>&amp;Phi;6 mm x 200 m</td></tr><tr><td>&lt;strong&gt;WS2&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>&amp;nbsp;tarp (blue) (1)</td><td></td><td></td><td>0.25 x 4500 x 4500 mm</td></tr><tr><td>bamboo rod (8)</td><td></td><td></td><td>15 mm x 2000 mm</td></tr><tr><td>PP rope (1)</td><td></td><td></td><td>&amp;Phi;6 mm x 200 m</td></tr><tr><td>&lt;strong&gt;WS3&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Plywood boards (2)</td><td></td><td></td><td>13 x 900 x 1800 mm</td></tr><tr><td>&amp;nbsp;joint (11)</td><td></td><td></td><td>for&amp;nbsp; &amp;Phi;48.6 mm</td></tr><tr><td>&amp;nbsp;tarp (blue) (1)</td><td></td><td></td><td>0.25 x 4500 x 4500 mm</td></tr><tr><td>bamboo rod (7)</td><td></td><td></td><td>15 mm x 2000 mm</td></tr><tr><td>PP rope (1)</td><td></td><td></td><td>&amp;Phi;6 mm x 200 m</td></tr><tr><td>&lt;strong&gt;WS4&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Plywood boards (2)</td><td></td><td></td><td>13 x 900 x 1800 mm</td></tr><tr><td>Plywood board (1)</td><td></td><td></td><td>13 x 900 x 900 mm</td></tr><tr><td>wood SPF 2x4</td><td></td><td></td><td>38 x 89 x1820 mm</td></tr><tr><td>cardboard</td><td></td><td></td><td>free size</td></tr><tr><td>wood screw (1 box)</td><td></td><td></td><td>3.3x50 mm</td></tr><tr><td>packing tape (2)</td><td></td><td></td><td>50mmx50m</td></tr><tr><td>peg (4)</td><td></td><td></td><td>&amp;Phi;9mmx300mm</td></tr><tr><td>&lt;strong&gt;Tool&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Impact driver</td><td></td><td></td><td>18v&amp;nbsp; 160N &amp;bull; m</td></tr><tr><td>Hammer</td><td></td><td></td><td>2 kg</td></tr><tr><td>Impact socket&amp;nbsp;</td><td></td><td></td><td>17mm</td></tr><tr><td>Bit for impact driver</td><td></td><td></td><td>+ 65mm&amp;nbsp;&amp;nbsp;</td></tr><tr><td>&lt;strong&gt;Software&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>AUTODESK FUSION 360 2.0.12164</td><td></td><td></td><td>Drawing designs</td></tr><tr><td>Blender (Version 3.0.0 2021-12-03)</td><td></td><td></td><td>Drawing designs</td></tr><tr><td>R</td><td></td><td></td><td>one-way ANOVA</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>video cameras</td><td>&amp;nbsp;(JVC, G Z -RX690-D)</td><td></td><td></td></tr></tbody></table>

four temporary waterslide designs adapted to different slope conditions to encourage child socialization in playgrounds

Increased urbanization has decreased children's access to various natural outdoor environments. To counteract this deficiency in early life experiences, we designed four temporary waterslides, each tailored to different city-side park conditions. The waterslides were simple to construct, with frames built from easy-to-attain resources such as bamboo rods from a local forest and simple pipes and joints overlaid by a tarp. Plywood boards, cardboard, and a tarp were used to create a pool at the foot of the slides, which were placed on existing slopes or stairs in each park. Water was continually released down the slide during each 1-2 h event. At each park event, children gathered spontaneously to use the slides and interact socially. No serious accidents occurred during the waterslide trials. To understand how the children used each waterslide, the activity at the waterslides was recorded by video. The minute of the highest activity level at the waterslide was quantitatively analyzed to determine the lines of flow surrounding the waterslide and the mean and maximum speeds attained while using the waterslide.

Children gathered, interacted socially, and played together at all the waterslides (Figure 4). Children using WS4 were estimated to be older that those at the other slides (Table 2). The representative child motion tracking pattern during 1 min of the maximum speed at each WS is visualized in Video 5. Figure 5 shows the representative IN-OUT line of motion around each waterslide. Two different motion lines, between substructure a and b, were detected for WS1 (Figure 5A). However, since the line at b did not connect to the waterslide, only the line at a was defined as being relevant to the waterslide. For waterslides with a pool at the bottom (WS1-3), some motion lines indicated use of the pool without using the slide (Figure 5A-C). Repeated up-and-down movement on the slide without exiting was also frequently observed (Figure 5A-C). Compared to WS1-3, the flow line for WS4 included repeated series of sliding down, then going up the side stairs, and sliding again without exiting (Figure 5D).
Additionally, we compared the mean and maximum movement of each individual child considering the area (Table 1) and the number of children using the waterslide (Figure 6A,B). The areas of WS1, WS2, and WS3 differed greatly from one another, but the children&#39;s level of movement at each were similar. The movement around WS4 was significantly higher than at the other slides.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64235/64235fig02.jpg" /> 
Figure 2: Waterslide designs. (A) WS1 at Park 1. (B) WS2 at Park 2. (C) WS3 at Park 3. (D) WS4 at School 4. Abbreviation: WS = waterslide. <a href="https://www.jove.com/files/ftp_upload/64235/64235fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64235/64235fig03.jpg" /> 
Figure 3: Quantification analysis application flowchart and protocol. See protocol step 3. <a href="https://www.jove.com/files/ftp_upload/64235/64235fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/64235/64235fig04.jpg" /> 
Figure 4: Scenes at the four waterslides. (A) WS1 at Kuroishi park. (B) WS2 at Kotosaki park. (C) WS3 at Kiwanami park. (D) WS4 at School 4. <a href="https://www.jove.com/files/ftp_upload/64235/64235fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/64235/64235fig05.jpg" /> 
Figure 5: Representative IN-OUT lines of motion around each waterslide. (A) WS1: The most representative line at substructure a was red. Two different patterns were also seen: a black line at a, using the pool only, or an individual red line at b, not directing to a. (B) WS2: Three patterns appeared: a blue line using the whole slide with high speed, a black line using the slide partially, and a red line staying in the pool. (C) WS3: Two red lines represented either using or not using the slope substructure. (D) WS4: The behavioral pattern was unified (they used the slide). A-D: a = pool, b = waterslide; red = out; green = in. Abbreviation: WS = waterslide. <a href="https://www.jove.com/files/ftp_upload/64235/64235fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/64235/64235fig06.jpg" /> 
Figure 6: Quantitative comparison of the four types of waterslides. Black circles represent means. Dots represent individual children. (A) The means of motion are compared. The numbers under WS1-4 labels indicate the highest number of children gathered on the slide during the same 1 min. (B) The maximum speed derived from the same data as A. * WS4 is significantly higher than the other WSs (one-way ANOVA, p &#60; 0.05). <a href="https://www.jove.com/files/ftp_upload/64235/64235fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td colspan="2">Park/School</td>
			<td>Date</td>
			<td>Time</td>
			<td colspan="2">Max Time</td>
			<td>Slide Area (m2)</td>
			<td>Slope (&#176;)</td>
			<td>Length (m)</td>
		</tr>
		<tr>
			<td colspan="2">Park 1 &#8220;Kuroishi&#8221;</td>
			<td>16-06-2019</td>
			<td>13:00-16:00</td>
			<td colspan="2">14:21:30-14:22:30</td>
			<td>3.2</td>
			<td>25.0</td>
			<td>1.8</td>
		</tr>
		<tr>
			<td colspan="2">Park 2 &#8220;Kotosaki&#8221;</td>
			<td>31-08-2019</td>
			<td>13:00-16:00</td>
			<td colspan="2">13:43:00-13:44:00</td>
			<td>12.0</td>
			<td>30.0</td>
			<td>6.0</td>
		</tr>
		<tr>
			<td colspan="2">Park 3 &#8220;Kiwanami&#8221;</td>
			<td>28-09-2019</td>
			<td>12:00-16:00</td>
			<td colspan="2">12:49:00-12:50:00</td>
			<td>8.0</td>
			<td>21.0</td>
			<td>4.0</td>
		</tr>
		<tr>
			<td colspan="2">School 4 &#8220;Kamiube&#8221;</td>
			<td>08-08-2021</td>
			<td>13:00-18:00</td>
			<td colspan="2">17:14:00-17:15:00</td>
			<td>5.4</td>
			<td>27.0</td>
			<td>6.0</td>
		</tr>
	</tbody>
</table>
Table 1: Times of the playpark events and analytical target time, and waterslide information.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td rowspan="2">WS #</td>
			<td rowspan="2">Number of children</td>
			<td colspan="2">Child height [cm]</td>
		</tr>
		<tr>
			<td>mean</td>
			<td>SD</td>
		</tr>
		<tr>
			<td>Park 1</td>
			<td>12</td>
			<td>130.4</td>
			<td>22.0</td>
		</tr>
		<tr>
			<td>Park 2</td>
			<td>5</td>
			<td>132.0</td>
			<td>14.7</td>
		</tr>
		<tr>
			<td>Park 3</td>
			<td>3</td>
			<td>116.7</td>
			<td>12.5</td>
		</tr>
		<tr>
			<td>School 4</td>
			<td>8</td>
			<td>147.5</td>
			<td>12.0</td>
		</tr>
	</tbody>
</table>
Table 2: Height (mean and standard deviation) of the children playing at each waterslide during the &#34;Max Time&#34;. The approximate heights of the children contributed to the prediction of age.
Video 1: The most active 1 min, &#34;Max time&#34;, at WS1 at Kuroishi Park. This waterslide was designed at a park with no slope. Having to build a slope for the waterslide resulted in the waterslide having a relatively smaller area compared to the other waterslides. Many children still played together at this waterslide. Abbreviation: WS = waterslide. <a href="https://www.jove.com/files/ftp_upload/64235/renamed_835d3.mp4" target="_blank">Please click here to download this Video.</a>
Video 2: The most active 1 min, &#34;Max time&#34;, at WS2 at Kotosaki Park. This waterslide was constructed at a park with a natural wide, steep (30&#176;) and long slope. There was variation in how children used this slide. Some children sped down the slide, while others carefully walked up and down. Abbreviation: WS = waterslide. <a href="https://www.jove.com/files/ftp_upload/64235/HUA_video2.mp4" target="_blank">Please click here to download this Video.</a>
Video 3: The most active 1 min, &#34;Max time&#34;, at WS3 at Kiwanami Park. This event took place in 2019 prior to the COVID19 pandemic. At this waterslide, younger children were seen playing for longer times on the gentle slope. <a href="https://www.jove.com/files/ftp_upload/64235/HUA_video3.mp4" target="_blank">Please click here to download this Video.</a>
Video 4: The most active 1 min, &#34;Max time&#34;, at WS4 at Kamiube School. The fourth waterslide event took place in 2021 during the COVID19 pandemic. At this waterslide, older children repetitively sped down the slide together. The use of the stairs in this design may have contributed to this behavior. <a href="https://www.jove.com/files/ftp_upload/64235/HUA_video4.mp4" target="_blank">Please click here to download this Video.</a>
Video 5: Each representative pattern of the most active child tracking motion at WS1-4. <a href="https://www.jove.com/files/ftp_upload/64235/4in1.mov" target="_blank">Please click here to download this Video.</a>
Supplemental File 1: Safety considerations and assembly. <a href="https://www.jove.com/files/ftp_upload/64235/Supplemental File 1.docx" target="_blank">Please click here to download this File.</a>
Supplemental File 2: Child motion tracking methods with Python codes and keynote files. <a href="https://www.jove.com/files/ftp_upload/64235/Supplemental File 2R.docx" target="_blank">Please click here to download this File.</a>

Watch this Scientific Journal Video about Four Temporary Waterslide Designs Adapted to Different Slope Conditions to Encourage Child Socialization in Playgrounds at JoVE.com

Four Temporary Waterslide Designs Adapted to Different Slope Conditions to Encourage Child Socialization in Playgrounds

Early life social learning is enhanced by interactions with effectively designed environments. Four events were held at different city parks using inexpensive, temporary waterslides to stimulate social learning. This study describes the prototypes used and the evaluation of the children&#39;s interactions.

Increased urbanization has decreased children's access to various natural outdoor environments. To counteract this deficiency in early life experiences, ...

four-temporary-waterslide-designs-adapted-to-different-slope

Research

JoVE Journal

Behavior

1.9K Views.  Yamaguchi University. Early life social learning is enhanced by interactions with effectively designed environments. Four events were held at different city parks using inexpensive, temporary waterslides to stimulate social learning. This study describes the prototypes used and the evaluation of the children's interactions.

Video: Four Temporary Waterslide Designs Adapted to Different Slope Conditions to Encourage Child Socialization in Playgrounds

Design and Construction of an Urban Runoff Research Facility

As the urban population increases, so does the area of irrigated urban landscape. Summer water use in urban areas can be 2-3x winter base line water use due to increased demand for landscape irrigation. Improper irrigation practices and large rainfall events can result in runoff from urban landscapes which has potential to carry nutrients and sediments into local streams and lakes where they may contribute to eutrophication. A 1,000 m2 facility was constructed which consists of 24 individual 33.6 m2 field plots, each equipped for measuring total runoff volumes with time and collection of runoff subsamples at selected intervals for quantification of chemical constituents in the runoff water from simulated urban landscapes. Runoff volumes from the first and second trials had coefficient of variability (CV) values of 38.2 and 28.7%, respectively. CV values for runoff pH, EC, and Na concentration for both trials were all under 10%. Concentrations of DOC, TDN, DON, PO4-P, K+, Mg2+, and Ca2+ had CV values less than 50% in both trials. Overall, the results of testing performed after sod installation at the facility indicated good uniformity between plots for runoff volumes and chemical constituents. The large plot size is sufficient to include much of the natural variability and therefore provides better simulation of urban landscape ecosystems.

This paper describes the design, construction, and function of a 1,000 m2 facility containing 24 individual 33.6 m2 field plots equipped for measuring total runoff volumes with time and collection of runoff subsamples at selected intervals for quantification of chemical constituents in the runoff water from simulated home lawns.

As the urban population increases, so does the area of irrigated urban landscape. Summer water use in urban areas can be 2-3x winter base line water use ...

Environment

Kinematic History of a Salient-recess Junction Explored through a Combined Approach of Field Data and Analog Sandbox Modeling

Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history within these junctions is best preserved in areas where thrust sheets extend from a salient through an adjacent recess. We examine one such junction within the Sevier fold-thrust belt (western United States) along the Leamington transverse zone, northern Utah. Deformation within this junction took place by faulting and cataclastic flow. Here, we describe a protocol that examines these fault patterns to better understand the kinematic history of the field area. Fault data is supplemented by analog sandbox experiments. This study suggests that, in detail, deformation within the overlying thrust sheet may not directly reflect the underlying basement structure. We demonstrate that this combined field-experimental approach is easy, accessible, and may provide more details to the deformation preserved in the crust than other more expensive methods, such as computer modeling. In addition, the sandbox model may help to explain why and how these details formed. This method can be applied throughout fold-thrust belts, where upper-crustal rocks are well preserved. In addition, it can be modified to study any part of the upper crust that has been deformed via elastico-frictional mechanisms. Finally, this combined approach may provide more details as to how fold-thrust belts maintain critical-taper and serve as potential targets for natural resource exploration.

Kinematic histories of fold-thrust belts are typically based on careful examinations of high-grade metamorphic rocks within a salient. We provide a novel method of understanding fold-thrust belts by examining salient-recess junctions. We analyze the oft-ignored upper crustal rocks using a combined approach of detailed fault analysis with experimental sandbox modeling.

Within fold-thrust belts, the junctions between salients and recesses may hold critical clues to the overall kinematic history. The deformation history ...

Image-based Lagrangian Particle Tracking in Bed-load Experiments

Image analysis has been increasingly used for the measurement of river flows due to its capabilities to furnish detailed quantitative depictions at a relatively low cost. This manuscript describes an application of particle tracking velocimetry (PTV) to a bed-load experiment with lightweight sediment. The key characteristics of the investigated sediment transport conditions were the presence of a covered flow and of a fixed rough bed above which particles were released in limited number at the flume inlet. Under the applied flow conditions, the motion of the individual bed-load particles was intermittent, with alternating movement and stillness terms. The flow pattern was preliminarily characterized by acoustic measurements of vertical profiles of the stream-wise velocity. During process visualization, a large field of view was obtained using two action-cameras placed at different locations along the flume. The experimental protocol is described in terms of channel calibration, experiment realization, image pre-processing, automatic particle tracking, and post-processing of particle track data from the two cameras. The presented proof-of-concept results include probability distributions of the particle hop length and duration. The achievements of this work are compared to those of existing literature to demonstrate the validity of the protocol.

The manuscript presents a protocol for the conduction of bed-load sediment transport experiments where the moving particles are tracked by image analysis. The experimental facility, the procedures for run realization and data processing, and finally some proof-of-concept results are presented here.

Image analysis has been increasingly used for the measurement of river flows due to its capabilities to furnish detailed quantitative depictions at a ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Engineering

A Standardized Obstacle Course for Assessment of Visual Function in Ultra Low Vision and Artificial Vision

We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. Six sighted controls and 36 completely blind but otherwise healthy adult male (n=29) and female (n=13) subjects (age range 19-85 years), were enrolled in one of three studies involving testing of the BrainPort sensory substitution device. Subjects were asked to navigate the course prior to, and after, BrainPort training. They completed a total of 837 course runs in two different locations. Means and standard deviations were calculated across control types, courses, lights, and visits. We used a linear mixed effects model to compare different categories in the PPWS (percent preferred walking speed) and error percent data to show that the course iterations were properly designed. The course is relatively inexpensive, simple to administer, and has been shown to be a feasible way to test mobility function. Data analysis demonstrates that for the outcome of percent error as well as for percentage preferred walking speed, that each of the three courses is different, and that within each level, each of the three iterations are equal. This allows for randomization of the courses during administration.
Abbreviations: 
preferred walking speed (PWS) 
course speed (CS) 
percentage preferred walking speed (PPWS)

We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. The course is relatively inexpensive, simple to administer, and has been shown to be reliable and reproducible.

We describe an indoor, portable, standardized course that can be used to evaluate obstacle avoidance in persons who have ultralow vision. Six sighted ...

Medicine

A Modified Lean and Release Technique to Emphasize Response Inhibition and Action Selection in Reactive Balance

Assessment of reactive balance traditionally imposes some type of perturbation to upright stance or gait followed by measurement of the resultant corrective behavior. These measures include muscle responses, limb movements, ground reaction forces, and even direct neurophysiological measures such as electroencephalography. Using this approach, researchers and clinicians can infer some basic principles regarding how the nervous system controls balance to avoid a fall. One limitation with the way in which these assessments are currently used is that they heavily emphasize reflexive actions without any need to revise automatic postural reactions. Such an exclusive focus on these highly stereotypical reactions would fail to adequately address how we can modify these reactions should the need arise (e.g., avoiding an obstacle with a recovery step). This would appear to be a glaring omission when one considers the enormous complexity of the environments we face daily. Overall, the status quo when evaluating the neural control of balance fails to truly expose how higher brain resources contribute to preventing falls in complex settings. The present protocol offers a way to require suppression of automatic, but inappropriate corrective balance reactions, and force a selection among alternative action choices to successfully recover balance following postural perturbation.

Here we offer a protocol that allows the user to selectively change affordances and/or constraints on movements that are relevant for recovering balance after postural perturbation.

Assessment of reactive balance traditionally imposes some type of perturbation to upright stance or gait followed by measurement of the resultant ...

A Training Program Using an Agility Ladder for Community-Dwelling Older Adults

Aging impairs physical and cognitive functions and limits daily activities. Agility training can improve or maintain physical functioning in older people. The purpose of this study is to report the physical fitness benefits of a training program for independent community-dwelling older adults using an agility ladder. Each training session lasted approximately 30 minutes, and the benefits were achieved with two sessions per week for 14 weeks. Training was timed and involved four different drills and varying levels of difficulty through time. The exercises were performed at the School of Physical Education of the University of Campinas, S&#227;o Paulo state, Brazil. The study participants (n = 16; mean age of 66.9 &#177; 5.0 years) were instructed to perform the exercises as quickly as possible without making mistakes and were assisted by a physical trainer when they made mistakes. Assessments were performed both before and after training using five functional tests (i.e., Illinois agility, five times sit-to-stand, timed up-and-go, walking usual speed, and one-leg stand). Although the study sample was not compared with a control group, the results indicate that training protocols using an agility ladder are easy and practical and improve physical function performance in older adults.

The aim of this study is to present an agility training program for older people. The feasibility of this program is described, and the training protocol demonstrated by video imaging.

Aging impairs physical and cognitive functions and limits daily activities. Agility training can improve or maintain physical functioning in older people. ...

Hydraulic Jumps

Source: Alexander S Rattner and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
When liquid flows along an open channel at high velocity, the flow can become unstable, and slight disturbances can cause the liquid upper surface to transition abruptly to a higher level (Fig. 1a). This sharp increase in the liquid level is called a hydraulic jump. The increase in the liquid level causes a reduction in the average flow velocity. As a result, potentially destructive fluid kinetic energy is dissipated as heat. Hydraulic jumps are purposely engineered into large water works, such as dam spillways, to prevent damage and reduce erosion that could be caused by fast moving streams. Hydraulic jumps also occur naturally in rivers and streams, and can be observed in household conditions, such as the radial outflow of water from a faucet onto a sink (Fig. 1b).
In this project, an open-channel flow experimental facility will be constructed. A sluice gate will be installed, which is a vertical gate that can be raised or lowered to control the discharge rate of water from an upstream reservoir to a downstream spillway. The flow rate required to produce hydraulic jumps at the gate outlet will be measured. These findings will be compared with theoretical values based on mass and momentum analyses.
<img alt="Figure 1" src="/files/ftp_upload/10405/10405fig1.jpg" /> 
Figure 1: a. Hydraulic jump occurring downstream from a spillway due to a slight perturbation to an unstable high-velocity flow. b. Example of hydraulic jump in radial outflow of water from a household faucet.

Hydraulic Jumps in Radial Outflow of Water

Source: Alexander S Rattner and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
When ...

Education

JoVE Science Education

Mechanical Engineering

Design Example: Designing Water Slide

When designing a water slide, controlling the speed of water flow is crucial for rider safety while maintaining an exciting experience. As water flows down the slide, gravity causes it to accelerate, with its speed at the bottom depending on the height from which it starts. The higher the slide, the more potential energy the water has at the top, which is converted into kinetic energy as it descends, increasing its speed.
Bernoulli&#39;s principle determines the water&#39;s velocity along the slide. The principle relates the potential energy at point 1, the top, the kinetic energy at point 2, the bottom, and the pressure of the water at both points.
<img alt="Equation 1" src="/files/ftp_upload/18040/18040_Equation_1.svg" style="text-align: center; height: 28px;" />
In a water slide, as the water moves downhill, its potential energy decreases while its kinetic energy increases, leading to an increase in velocity. Bernoulli&#39;s equation assumes no friction and treats water as an ideal fluid, meaning it flows without energy loss due to friction or turbulence. These assumptions simplify the calculations, though in real-world scenarios, friction may slightly reduce the actual speed of the water.
At the top of the slide, the water is nearly at rest, and as it descends, it accelerates. If the slide is too tall, the water can reach unsafe speeds at the bottom, posing risks to riders. Therefore, adjusting the slide&#39;s height h is necessary to keep the water&#8217;s velocity within safe limits. By calculating the appropriate height using Bernoulli&#39;s principle, the slide can reduce the water&#8217;s speed while offering a thrilling ride.
<img alt="Equation 2" src="/files/ftp_upload/18040/18040_Equation_2.svg" style="text-align: center; height: 36px;" />

An engineer is designing a waterslide for a water park, where water flows down to create a fast yet safe ride for park visitors.
The slide is 25 meters ...

JoVE Core

Civil Engineering

Unit 1

Fluid Dynamics

KEY TERMS AND CONCEPTS

Design Example: Creating a Hydraulic Model of a Dam Spillway

Scaled hydraulic models of dam spillways provide a practical way to replicate and study the intricate flow dynamics of these structures. Often built to a 1:15 ratio, these models allow for observing critical water behavior, such as velocity distribution, flow patterns, and energy dissipation.
<img alt="Equation 1" src="/files/ftp_upload/18074/18074_Equation_1.svg" style="text-align: center; height: 38px;" />
Through this controlled setup, researchers can closely examine how water flows over the spillway, supporting a detailed analysis of its performance. A fundamental principle behind these models is using Froude number similarity, which preserves the proper balance between gravitational and inertial forces.
<img alt="Equation 2" src="/files/ftp_upload/18074/18074_Equation_2.svg" style="text-align: center; height: 38px;" />
This similarity is essential, as it ensures that free-surface flow characteristics, including wave formation, turbulence, and flow separation, behave as they would in the full-sized structure. By achieving this accurate representation, scaled models provide valuable insights into how water interacts with spillway features, helping to pinpoint areas where the design might benefit from adjustments to enhance safety or flow efficiency.
In the scaled model, adjustments are also applied to discharge rates, flow velocities, and timing to reflect real-world conditions without requiring extensive water volumes or prolonged test durations. The discharge rate, for example, is reduced by the scale factor to maintain manageable flow rates, enabling safe experimentation.
<img alt="Equation 3" src="/files/ftp_upload/18074/18074_Equation_3.svg" style="text-align: center; height: 36px;" />
Additionally, time is compressed so that events unfolding over an entire day in the full-scale structure can be examined in just a few hours within the model.
<img alt="Equation 4" src="/files/ftp_upload/18074/18074_Equation_4.svg" style="text-align: center; height: 48px;" />
This efficient scaling supports rapid testing and analysis of different flow conditions and potential structural responses. Overall, scaled modeling of spillways is crucial for assessing designs, identifying potential vulnerabilities, and confirming that the full-scale structure will perform reliably under various water flow conditions.

A hydraulic model of a dam spillway is often created by scaling down the design, typically to a 1:15 ratio, to replicate key flow characteristics such as ...