6 Methods to Organize Disaster Risks of Solar Power Plants with Drone Surveys

Solar power plants are facilities that encompass many assets to manage, such as large sites, slopes, drainage facilities, access roads, fences, embankments, and surrounding woodlands. While routine inspections tend to focus on power generation equipment, disaster risks—such as heavy rain, typhoons, earthquakes, snowfall, soil runoff, fallen trees, and flooding—can lead not only to reduced power output but also to equipment damage, impacts on surrounding areas, and delays in restoration work. In organizing these risks, drone surveying is one means of gaining an aerial overview of the entire site and recording the condition of terrain and structures.

However, conducting drone surveying does not automatically identify all disaster risks. Only by organizing the imaging coverage, flight plan, reference coordinates and elevations, comparison with past data, combination with on-site inspections, and the way records are kept does the data become information that is useful for disaster countermeasures. This article explains six methods that operational staff at solar power plants can use to organize disaster risks using drone surveying, presented in a workflow that is easy to use on site.

Table of Contents

• Why drone surveying helps organize disaster risk at solar power plants

• Method 1: Understand the site's overall topography and elevation differences

• Method 2: Identify drainage routes and locations where water tends to accumulate

• Method 3: Record deformations in slopes and engineered embankments

• Method 4: Determine the extent of impacts on panel racking and access/maintenance roads

• Method 5: Store data so it can be compared before and after disasters

• Method 6: Combine on-site inspections with drone survey results

• Key points for embedding disaster risk organization into continuous operations

• Summary

Why Drone Surveying Helps Organize Disaster Risk at Solar Power Plants

Disaster risks at solar power plants cannot be fully understood by looking only at the generation equipment itself. Even if panels and mounting racks show no obvious damage, there may be small collapses on surrounding slopes, sediment accumulated in drainage channels, or subsidence and scouring on parts of access roads. These changes can be missed by inspections conducted only from the ground. It is especially important to grasp the overall picture at large sites, on sloped terrain, near forests, or where there are multiple drainage routes.

One advantage of drone surveying is that it can continuously record a site from above. By creating bird's-eye images and orthophotos, it becomes easy to check the overall site layout, drainage directions, slope locations, maintenance roads, fence lines, and their relationships with the surrounding terrain as if on a single drawing. Also, by regularly recording the same area, it becomes easier to compare vegetation growth, sediment movement, blockage of drainage facilities, and changes to the ground surface.

What matters in organizing disaster risk is not just detecting anomalies, but being able to explain where risks exist, how severe they are, and which facilities or operations they might affect. For example, if there is a low spot where water tends to collect during heavy rain, the priority of countermeasures will change depending on whether there are power conditioners, collection boxes, access roads, openings in fences, or drainage outlets to adjacent land nearby. Using images and topographic information obtained from drone surveys, you can visually organize these relationships.

On the other hand, relying too heavily on drone surveying can make it difficult to assess subsurface conditions or the detailed structural integrity of constructions that are not apparent from visual inspection. Therefore, it is practical to use drone surveying as an entry point for organizing disaster risk and, as needed, combine it with on-the-ground verification, specialized surveying, civil engineering investigations, and equipment inspections. For site personnel, an effective approach is to first obtain a broad overview, then narrow down priority areas, and finally translate those findings into countermeasures and records.

Method 1: Understand the Site's Overall Topography and Elevation Differences

The first step in assessing disaster risks at a solar power plant is to grasp the terrain of the entire site. Solar power plants may be installed not only on flat land but also on reclaimed or engineered land, sloped terrain, valley formations, and locations involving cuts and fills in forested areas. Even if the site appears to be leveled, there can be gentle elevation differences within the site, directions in which water tends to flow, places where sediment is likely to accumulate, and low-lying areas prone to inundation.

In drone surveying, you can organize the shape of a site and the trends of the ground surface based on images taken from above. When checking elevation differences, it is important not just to take photographs but to establish survey control points and reference markers according to the required accuracy so they can be compared later. For disaster risk assessment, it is helpful to understand not only absolute heights but also which parts of the site are higher or lower and the directions from which water or debris are likely to flow in from the surrounding area.

Particularly important to check are locations where water from the upper slope could flow into the power plant site, depressions within the site that tend to retain water, embankment sections created during site development, crossings of maintenance roads, and drainage outlets at fence lines. Having an overview of the spatial relationships among these points makes it easier to prioritize inspections before heavy rain and patrols after typhoons.

When preparing the terrain, it's important not to rely solely on the layout plan of the power generation equipment. Even if the design drawings show neat plots, the actual ground surface may still have subtle irregularities from construction, settlement over time, ruts, and sediment buildup. Recording the current conditions with drone surveys makes it easier to verify discrepancies between the drawings and the actual site conditions.

Also, when organizing disaster risks, the area outside the site cannot be ignored. If there are forests, farmland, rivers, waterways, roads, or constructed slopes around the perimeter of a solar power plant, inflows of water or sediment from outside the site can lead to damage within the plant. If drone surveying is limited to within the site only, you may overlook the causes of such risks. After confirming the permissible flight area, obtaining permission from landowners and stakeholders, and taking the surrounding environment into consideration, recording the connections with the surrounding terrain will make the materials easier to use as explanatory documents for disaster countermeasures.

Method 2 Check drainage paths and areas where water tends to collect

Among the disaster risks at solar power plants, poor drainage associated with heavy rain and typhoons is an important item to check. When rainwater ponds on site, it can lead to muddy maintenance roads, slope erosion, washout of soil around racking foundations, impacts on buried cable sections, and reduced workability around equipment. Even if drainage ditches and catch basins are installed, their function may be degraded by sediment, fallen leaves, vegetation, and inflowing debris.

Using drone surveying, you can continuously inspect drainage routes from above. During ground patrols, drainage channels are often checked at discrete points, but viewing from above makes it easier to understand the flow of water across the entire site, the continuity of drainage channels, locations prone to water collection, and downstream outlets. In particular, drainage paths that cross beneath rows of panels, side ditches that are easily hidden by grass, and drainage lines along fences are worth recording during normal conditions.

The main point to check is not just whether drainage facilities are present, but to verify the flow as a whole—where the water comes from and where it exits. When water flowing in from the upper slope crosses the access road, passes beneath the panels, and flows into an off‑site water channel, inspect whether there are points along that route that are prone to clogging. If conditions such as a narrow outlet, a gentle gradient, accumulated sediment, dense vegetation, or an off‑site receiving channel that easily clogs coincide, short, intense rainfall can more readily cause flooding or scouring.

Drone survey imagery is also useful when sharing inspection results with stakeholders. Ground photos alone can make it difficult to convey which drainage channel and exactly where the problem is, but organizing locations on orthophotos makes it easier to align understanding among the management company, the contractor, maintenance personnel, and the owner. When requesting restoration work after a disaster, being able to show the affected area in advance also helps streamline on-site inspections.

When assessing drainage risk, it is also important not to rely too much on imagery taken only in clear weather. In fine weather water is not flowing, so the actual rainwater pathways can be difficult to discern. Within limits that allow you to ensure safety, checking after rain for surface wetting patterns, traces of soil erosion, mud deposits, and clogged drains makes it easier to identify where water actually moved. However, avoid flying in bad weather or strong winds, and prioritize flight conditions and safety management.

Method 3 Record deformations of slope faces and constructed fill areas

When a solar power plant is located on developed sites or slopes, the condition of slopes and cut-and-fill sections becomes central to disaster risk management. Small cracks, bulging, surface scour, collapses around drainage channels, sediment accumulation at the toe of slopes, and vegetation loss are often hard to notice in the early stages. However, if deterioration progresses after heavy rain or earthquakes, it can affect access road passability, fence stability, safety around panel mounting structures, and the outflow of sediment onto adjacent land.

With drone surveying, slopes can be photographed from oblique upward or near-frontal angles, allowing you to record areas that are hard to see from the ground. On high slopes or slopes that are difficult to access, it can be dangerous for ground personnel to approach and inspect. Using drones makes it possible to photograph the entire area while maintaining a safe distance, making it easier to identify potential abnormal spots while reducing the risk of entry during inspections.

When documenting slope surface changes, it is important to record continuously from the same position, the same direction, and a similar altitude and field of view, rather than relying on single photographs. If there is no record of the pre-disaster condition, it becomes difficult to determine whether cracks or collapses found after the disaster are new or existed previously. Keeping regularly taken photographic records makes it easier to confirm whether changes have occurred and provides material for decisions on repairs or detailed investigations.

Particular attention should be paid to locations where water concentrates and falls from the upper part of a slope, around the outlets of drainage channels, where sediment accumulates at the toe of slopes, around retaining walls and small benches, and sites where vegetation has been unnaturally stripped. These spots are easier to assess when aerial images are combined with close-up ground photographs. It is practical to verify candidate locations found by drone surveys on site and, if necessary, refer them for specialist judgment.

Records of slopes and developed areas are also important as explanatory materials after a disaster. If damage occurs, it is necessary to show when, where, and to what extent changes occurred. If the extent is recorded using drone surveys, it becomes easier to compare before and after restoration, confirm repair areas, and consider measures to prevent recurrence. From the stage of organizing disaster risks, it is important to be mindful of how to keep records so they can be explained later.

Method 4 Organize the scope of impacts on panel mounting structures and management roads

When organizing disaster risks, it is necessary to understand not only the terrain and drainage but also the extent of impacts on power generation equipment and maintenance/access routes. In a solar power plant, panels, racking, foundations, cables, collection equipment, access roads, fences, gates, and drainage facilities are interrelated. For example, even if a small slope failure does not reach the panels directly, it can block an access road or impede the passage of inspection vehicles. If poor drainage concentrates under certain rows of panels, it can affect the ground conditions around the racking foundations.

By surveying the entire site with a drone, it becomes easier to organize the relationship between risk locations and equipment placement. You can visually identify which equipment is near low-lying areas prone to flooding, which trees that could fall are close to which rows of panels, and which access roads would become unusable if soil erosion occurs. This makes it easier to prioritize based not merely on listing hazardous spots but on their potential impact on power plant operations.

Management roads are particularly important for recovery work during disasters. If roads within a power plant become impassable due to scouring, subsidence, sediment accumulation, or fallen trees, inspections and material deliveries are delayed. By recording the grade, shoulders, drainage crossings, bends, and sections adjacent to slopes of management roads with drone surveying, you can organize which sections are most susceptible to damage. After heavy rain, you can check from above for changes in pavement color, sediment buildup, deepening ruts, and shoulder collapse to narrow down priority areas for ground inspection.

Around the panel racking, check for exposed foundations, scouring of the ground surface, accumulation of sediment, and reduced visibility caused by vegetation. Drone surveying alone cannot determine the structural integrity of the racking, but it is useful as a means to broadly identify areas where abnormalities are suspected. In particular, if only part of a row shows a change in ground-surface conditions, or if drainage flow is concentrated around the racking foundations, those areas should be followed up with detailed on-site inspection.

When organizing disaster risks, it is also important to view the impacted area broadly. Check not only the damaged locations themselves but also the approach routes to them, access routes for restoration vehicles, temporary storage sites, drainage outlets, and boundaries with adjacent properties. By overlaying inspection routes and points of concern on current-condition images produced by drone surveys and managing them that way, it becomes easier to decide which parts of the power plant to protect first and where to begin restoration.

Method 5 Store data so that data before and after a disaster can be compared

The storage of baseline data collected during normal conditions is critically important for leveraging drone surveying in disaster risk management. Even if you capture images after a disaster, you can record the extent of the damage, but to determine where and how much has changed compared with before, you need reference data for comparison. Organizing pre-disaster orthophotos, oblique photographs, flight routes, capture dates, capture conditions, control point information, and inspection notes makes it easier to confirm changes after a disaster.

For use in comparisons, it's important to keep imaging conditions as consistent as possible each time. If imaging altitude, imaging area, image overlap, handling of control points, file formats, and file naming vary, it becomes more time-consuming to compare later. When the goal is disaster risk assessment, it's useful to establish a basic imaging route for comparisons during normal conditions so that you can record the same area at regular inspections, before heavy rain, before typhoons, and after disasters.

When storing data, you should preserve not only photos and survey results but also information that makes clear what the data represent. Recording the capture date, weather, photographer, target area, flight purpose, special notes, and observations made on site helps ensure the information remains meaningful when another person checks it later. Even if only the files remain, if it's unclear what area was captured and for what purpose, they become difficult to use as materials for disaster response.

In post-disaster comparisons, it is also important not to draw immediate conclusions about locations where changes are observed. Areas that appear to change color in images may be sediment runoff, exposed ground after mowing, shadows, or differences in moisture, and on-site verification may be necessary to determine which. Drone surveying has the ability to detect changes, but ground checks and cross-referencing with relevant materials are indispensable for judging their causes and levels of risk.

The way data is stored affects the initial response when a disaster occurs. If necessary data is stored only on a staff member's personal device, it may not be shareable in an emergency. By deciding for each power plant the data storage location, naming rules, how to manage the latest versions, and which stakeholders can view them, you can immediately compare with past data after a disaster. For drone surveys of solar power plants, it is more important to preserve the data in a form that can be used later than to simply capture images.

Method 6 Combining On-site Verification and Drone Survey Results

Drone surveying is an efficient way to assess large areas, but on-site verification is necessary for final judgments of disaster risk. There are limits to the information visible from above. Blockages inside drainage channels, fine cracks in mounting foundations, weak ground, loose fence posts, damaged cables, and signs of water ingress into equipment may not be fully verifiable from drone imagery alone. Therefore, it is important to establish a workflow that extracts candidate locations from drone surveys and conducts focused on-the-ground inspections.

In practice, we first use drone surveys to check the entire site and organize locations that appear to be high risk. Then, during on-site patrols, rather than visiting every area with the same density, we prioritize locations where poor drainage is suspected, slopes showing deformation, management roads that are prone to damage, and risk points near equipment. This makes it easier to reduce oversights even with limited time and personnel.

At on-site inspections, it is effective to bring images obtained from drone surveys so you can cross-reference the inspection locations. If you have materials with markings on the aerial images, it becomes easier to share exactly which spot is being viewed on site. This is especially true at power plants where rows of panels are continuous, since similar scenery makes it easy to confuse locations. Using the results of drone surveys as guide maps for ground patrols can reduce missed checks and duplication.

It is also important to integrate the results of on-site inspections back into the drone survey data. Recording field-confirmed sediment accumulation, clogged drains, slope cracks, shoulder subsidence, etc., linked to the location information on the aerial images makes it easier to compare during the next inspection. Rather than simply taking photos on site, organizing which position in which image corresponds to each finding improves the accuracy of disaster risk management.

When combined with on-site inspections, safety management is indispensable. Slopes after disasters, wet management roads, partially collapsed slopes, areas around fallen trees, and flooded spots can remain hazardous. If drone surveying allows an overall assessment first, potential hazard locations can be identified before anyone approaches. This supports decisions to avoid entering areas unnecessarily and, when needed, to inspect from a safe distance. Drone surveying not only helps organize disaster risks but also serves as a supplementary means to improve the safety of inspection work.

Key Points for Integrating Disaster Risk Assessments into Ongoing Operations

The disaster risk assessment for solar power plants is not a one-time task. The conditions of terrain, drainage, vegetation, slopes, and access roads change with the seasons, the weather, and the state of maintenance. In particular, the points that need to be checked differ before and after the rainy season, the typhoon season, the snowy season, and periods of frequent strong winds. By incorporating drone surveying into ongoing operations, it can be used both for preventive inspections before a disaster and for early post-disaster checks.

For continued operation, it is important to decide the timing of imaging in advance. Options include carrying out imaging several times a year as part of routine inspections, conducting pre-inspections before forecasts of typhoons or heavy rain, and performing emergency inspections after disasters. You do not need to do everything the same way every time, but separating a basic coverage for comparison from areas of focused inspection makes management easier. For example, record the entire site regularly, while slopes, drainage channels, maintenance roads, and adjacent forested land are checked intensively before and after disasters.

Next, standardize the method for organizing risks. If each person uses different expressions, judgments will vary even for the same conditions. Deciding on classification criteria—such as locations prone to flooding, locations prone to sediment accumulation, locations suspected of slope deformation, locations likely to be affected by fallen trees or branches, and locations where passage on maintenance roads may be obstructed—will make it easier to compare consistently over time. Creating risk maps for each power plant based on drone survey results and updating them at each inspection is also an effective method.

Also, disaster risk assessment may not be completed solely by the power producer. Maintenance personnel, contractors, civil engineering staff, landowners, nearby stakeholders, and personnel involved in administrative procedures — multiple parties may need the information.

Drone survey images serve as materials that make it easy to convey the situation even to those without specialized knowledge. However, rather than providing images alone, it is important to supplement them in writing with where the location is, what concerns exist, and what responses are necessary.

From an operational perspective, flight safety and legal compliance are also prerequisites. It is necessary to check the terrain around the power plant, third-party access, distances to roads and residences, power lines and communication lines, weather conditions, and any conditions that require flight permits or approvals, and to develop a safe flight plan. After a disaster the site may differ from its normal state, so take care to verify takeoff and landing locations, access limits, and emergency response procedures. The basic operational principle is to avoid causing new accidents during flights conducted to assess disaster risk.

Finally, it is important to make drone surveying a system that leads to improvements rather than just a recording task. By linking survey results to concrete actions—cleaning drainage channels, repairing slopes, maintaining access roads, cutting vegetation, reviewing inspection routes, preparing restoration materials—the value of disaster risk management is increased. Not only storing each set of images, but also recording findings, response status, and points to check at the next inspection will enhance the continuity of power plant management.

Summary

To organize disaster risks at solar power plants, it is necessary to consider not only the power generation equipment but also the terrain, drainage, slopes, developed areas, access roads, and the surrounding environment as a single system. Drone surveying helps by providing an overhead view of large sites and by capturing changes that are easy to miss during ground patrols. In particular, paying attention to overall site elevation differences, the flow of rainwater, slope deformation, impacts on access roads, before-and-after disaster comparisons, and coordination with on-site inspections leads to a practical, field-usable risk assessment.

The important thing is not to let drone surveying end with a single flight. By retaining baseline data from normal conditions, enabling before-and-after comparisons for disasters, and managing that data linked to on-site inspection results, it becomes easier to use for early detection of damage and for recovery decision-making. In addition, aerial imagery and current-condition data are effective materials for explaining the situation to stakeholders.

However, it is not possible to determine all disaster risks using drone surveying alone. As needed, it is important to combine it with ground inspections, specialized surveying, civil-engineering investigations, and equipment inspections. Grasp the situation broadly, narrow down priority areas, keep records, and use them to drive improvements. By establishing this workflow, disaster risk management for solar power plants becomes more practical.

If you use drone surveying at a solar power plant, recording current conditions not only during disasters but also in normal times is an important preparedness measure. By continuously tracking changes to the site and visualizing the condition of drainage, slopes, and access roads, you can improve the accuracy of inspections and countermeasures. If you want to efficiently organize on-site disaster risks, it is important to consider operating drone surveys that match the plant’s conditions, surrounding environment, required accuracy, and safety management system.