the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Apr 2025
Integrating Hydrodynamic Modelling and Remote Sensing for Spatiotemporal Analysis of Wadi Thuwal Basin Flood Hazards Affecting the Haramain Train Pathway
Abstract. Spatiotemporal analysis to create accurate flood simulations in arid environments and hydrological unmeasured valley basins is one of the most important challenges in flood risk studies. This study investigated the flood risks that the torrents of the Wadi Thuwal Basin pose to the Haramain Train Pathway in various time and space scenarios. It also examined the potential impacts of climate change and environmental alterations on flood risks. The research aims to develop a comprehensive risk management plan that mitigates the possible negative consequences associated with floods. To achieve these goals, remote sensing, and high-resolution data from LiDAR, geological, topographic, and soil maps were processed using GIS. The Hydrological Engineering Center-Hydrologic Modeling System (HEC-HMS) was used to derive the hydrograph of torrential waters and the hydraulic model of the Hydrologic Engineering Center-River Analysis System (HEC-RAS) to simulate the Wadi Thuwal flood. This involved creating maps of torrential waters' velocity, depth, and spread, and evaluating the hydraulic installations under the train pathway. This study presents important planning considerations for policymakers in the KSA, given the paramount importance of the two holy cities of Makkah and Al-Madinah and the crucial role of the Haramain Train Pathway in ensuring safe connectivity between them.
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Status: final response (author comments only)
- RC1: 'RC', Anonymous Referee #1, 19 Jun 2025
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RC2: 'Comment on egusphere-2025-4', Anonymous Referee #2, 13 Sep 2025
This study models flood risks in the Wadi Thuwal Basin to assess potential impacts on the Haramain Train Pathway, incorporating climate change scenarios and GIS-based hydrological simulations to support comprehensive risk management planning in Saudi Arabia.
First, I think the research purpose of the entire article is not clear enough, and the superiority of the 2-D model is not demonstrated. In Line 309, the paper mentions that “two-dimensional modelling is considered a solution for evaluating flood problems concerning infrastructure.” However, there is a lack of comparison with 1-D modelling.
Secondly, I think the paper’s understanding of remote sensing is not deep enough. Apart from satellite imageries, no other remote sensing methods or data are used. Remote sensing is not just about looking at a satellite imagery. Since this is a study on floods, I think it could incorporate meteorological remote sensing data to analyze.
In conclusion, I think this paper requires substantial revision, which is more than a major revision. I would like to reject the manuscript but encourage resubmission.
Other minor revisions:
Line 77: Why does a 1D simulation make it hard to see the depth, speed, and flood spread? Could you please explain the reason?
Figure 2: There are many disputed borders. As a geoscience academic paper, it should not be involved in politics. I suggest that the authors remove all international borders outside Saudi Arabia, and all country name labels. In addition, the name of Qatar is misspelled; it is not “Qater.” However, I recommend removing all country name labels to avoid controversy. Just focus on geoscience.
Line 179: Regarding the Geometric Hydrological Model mentioned in the paper, what input parameters are included? Over what length of time series is the simulation performed?
Line 193: What the unit “1.87” specifically represents? Is it a converted index or a dimensionless parameter?
Line 203: Does this report have a citation? Which year of the IPCC report is this conclusion based on? Why was the most extreme scenario (RCP 8.5) chosen?
Line 251: Please briefly introduce the frequency ratio (FR) model and the Shannon’s entropy (SE) model, especially their scope of application.
Line 253: This paragraph is unclear. Under what circumstances was the hydraulic analysis carried out? How can these analyses verify the results of the two-dimensional spatiotemporal modeling?
Citation: https://doi.org/10.5194/egusphere-2025-4-RC2
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- 1
The authors have applied hydrodynamic modeling and remote sensing for flood hazard modeling in Wadi Thuwal Basin. The methods used in the study are appropriate and here are my comments.
Manuscript Title: The manuscript title is too long and should be more concise. For example; Hydrodynamic Modeling and Remote Sensing for Flood Risk Modeling in Wadi Thuwal Basin or Flood Risk Modeling of the Haramain Train Pathway in Wadi Thuwal Basin.
Abstract: The authors did a fine job of providing context for their study however, did not provide sufficient justification for the problem of flooding affecting the Haramain train pathway. For example, did the Aramain train pathway experience past or recent floods? Are floods anticipated in the future and why? I think providing some justification would strengthen the abstract.
Introduction: The introduction is well-written and I only have a minor suggestion regarding the structure. I suggest the author cut lines 67 to 75 and include in the introduction’s opening paragraph to set precedence and background on the issues of flooding in the Wadi Thumal Basin before other literature discussions. The authors can close the introduction with the objectives or goals of what they intend to achieve for their work. Additionally, labeling of the figures in Figure 1 is suggested, e.g. A and B with train views explained.
Materials and methods: Was there a reason why the authors used both the LiDAR-derived DEM and a topographic map? One would imagine that the LiDAR-derived DEM would be sufficient for the study because the LIDAR-derived DEM is in 3D and offers more detail. Also, other terrain geomorphometric parameters can be derived.
Results: In the validation section, did the authors compare the model results to existing flood hydrographs or other accurate measured/observed related parameters within the basin? An example is comparing the model flood depth to measured flood depth or comparing model flow/discharge within the area of interest to measured/observed flow/discharge within the basin. I suggest the authors clarify this in their manuscripts as the sources of data validation weren't clearly mentioned.
General observation: Could the authors check the figures, specifically figures 2, 3, 16, 21, 22 to ensure consistency? I suggest the authors check the model maps for accurate orientation to the Haramain train pathway. In the study area figure (figure 2), the Haramain train pathway seems to intersect the drainage basin pour point which is west of the map. However, the modeling results show the drainage basin pour point to be on the opposite direction which is the east of the map. If this is a zoomed-in version, I suggest the authors clarify this and if it's a projection error, I suggest the authors should fix it. Also, the authors should visually show the portion of the basin their simulation or analysis focuses on. Most readers are most likely unfamiliar with the location and presenting different map scales of the study area could be confusing especially when the entire Wadi Thuwal basin was not modeled. I suggest authors be consistent with map scale or show where they’re hydrodynamic modeling focuses on with respect to the Haramain train pathway.