the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
An optimized LSTM-based approach applied to early warning and forecasting of ponding in the urban drainage system
Wen Zhu
Tao Tao
Hexiang Yan
Jieru Yan
Jiaying Wang
Shuping Li
Kunlun Xin
Abstract. An optimized LSTM-based approach applied to early warning and forecasting of ponding in the urban drainage system is proposed in this study. This approach can identify locations and process of ponding quickly with relatively high accuracy. The model is constructed with two tandem processes and a multi-task learning mechanism is introduced. The results are compared with those of widely used neural networks (LSTM, CNN) to validate its advantages. Then, the model is revised with available monitoring data in the study area to achieve higher accuracy, and the influence of the number of the monitoring points selected on the performance of the corrected model is also discussed in this paper. Over 15000 designed rainfall events are used for model training, covering a diversity of extreme weather conditions.
Wen Zhu et al.
Status: final response (author comments only)
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RC1: 'Comment on egusphere-2022-874', Anonymous Referee #1, 29 Dec 2022
This paper proposed an optimized LSTM-based model applied to early warning and forecasting of ponding in the urban drainage system. It can identify flooding locations and process of ponding quickly with relatively high accuracy. The research ideas and methods are well innovative.
The issues are listed as follows:
-My main concern about this paper is related to the case area. The authors said "(Due to these structural characteristics) the performance of the model will not be limited by the size of the case area", but they only applied the proposed method to a small-scale case area (a residential district of 6.128 hm2). I think it would be necessary to explain the capability of the proposed method.
- Section 2.4.2 (Eq. 5) Why you used this formula to design rain intensity? This is the design formula used by the municipality (i.e. a routine in China), orï¼ Need specify.
- What is Pilgrim & Cordery? Any equations?
- Please show equations to explain how you added the noise as the description is not clear enough.
- Why there are only 5 real-world rainfall events to verify the performance of the corrected model? If it is enough considering that you have 16960 synthetic rainfall events?
- It is recommended to add HESS's article to the referencesã
Citation: https://doi.org/10.5194/egusphere-2022-874-RC1 -
AC1: 'Reply on RC1', Zhu Wen, 20 Jan 2023
Dear Reviewers,
Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits. We also appreciate your clear and detailed feedback and hope that the explanation has fully addressed all of your concerns.
Please see attachment for details.
Sincerely,
The Authors
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AC1: 'Reply on RC1', Zhu Wen, 20 Jan 2023
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RC2: 'Comment on egusphere-2022-874', Anonymous Referee #2, 20 Feb 2023
The authors proposed an LSTM-based emulator to simulate the ponding process in the drainage system, which is critical to urban flooding study. The emulator is composed of two LSTM models to sequentially simulate node lateral flows and the ponding volume, followed by a correction model. The proposed emulator was successfully applied to a case study and showed superior performances over some simplified versions (e.g., a lumped model using LSMT/CNN). I appreciate the hard work that has been put in by the authors. However, I have the following concerns which might require further revision before the manuscript can be accepted.
First of all, I had a hard time following the manuscript. Readability is critical to a renowned journal such as HESS. The current status of the manuscript does not meet the requirement. For example, there are a lot of run-on sentences. A rule of thumb is that the length of a sentence does not exceed two lines. Coherence is also an issue. Many sentences are 'loosely' connected in a logical sense. It would be a pity if the message is not clearly communicated while so much work has been done. I suggest the authors further greatly revise the language (a professional English editor might help in this case).
The second issue is associated with the model CR of the LSTM-based emulator (btw, what is CR abbreviated for?). I don't quite understand the descriptions of the model CR (i.e., L153-166). Neither Figure 6 is illustrative to me. Do the monitoring data refer to the measured lateral flows at the monitored nodes? Is the correction model trained on pairs of simulations and monitored measurements or based on a pre-trained mapping (i.e., using transfer learning)? Please specify.
The last concern is the mass balance of the emulator. Though not an expert in urban drainage systems, I consider that the mass conversation plays a key role in balancing the water exchanges between nodes. Does the proposed LSTM model account for that? If not, please specify the reason for not doing this.
Other minor edits:
L37-40: The authors point out the importance of the dataset. I'm wondering whether the author performed a sort of convergence test to evaluate how much data is sufficient for the proposed LSTM emulator training.
L50: 'not discussed' --> 'not explored'; 'not available' --> 'not feasible'
L77: 'influencing' --> 'influential'
L82: 'MAE, MSE, CC, NSE' --> We usually put full names before abbreviations
Figure 2 caption: '... test process in the runoff process' --> '... test procedures in developing the LSTM-based runoff emulator'. Also, many captions are too brief to provide enough information about these complicated figures.
Figure 3: For each of the two emulated processes, is only one LSTM used for all nodes? Or, is a separate LSTM used for each node?
L91-93: That's a super long sentence and there are a lot!
L100-102: Are the classification module and OUT_MODULE also two MLPs?
L105-106: I don't understand which layer in the LSMT module is shared by the classification and out modules.
L116-119: To evaluate the impact of the gaussian filter, is there a comparison between the current emulator and one without the gaussian noising procedure?
Eqs(1)-(4): I suggest moving the calculation of the error term to the appendix to improve the readability.
Eq.(5): What is 'lg'? Please use 'log' if you mean logarithm operation.
L195: 'tb and ta is' --> 'ta and tb are'
L197: Is Pilgrim & Cordery a reference? If yes, please provide the year.
L226: I like the usage of hyperopt here.
L229-231: missing subjects of the two sentences.
Table 3: What are the optimal hyperparameters of the MLP used for model CR? i.e., the number of neurons in each layer and the number of hidden layers. How about the hyperparameters of the classification and out modules?
L274: Why are these six nodes selected? (also shown in Figure 9)
Figure 10: It is the emulated ponding volume before the model correction or CR, right? If yes, why is it different from the lines labeled by 'Before updating' in Figure 11?
L336-341: Should these sentences be grouped into one paragraph?
Figure 15: combining (a) and (b)?
L338: 'In a summary' --> 'In summary'
Citation: https://doi.org/10.5194/egusphere-2022-874-RC2 -
AC2: 'Reply on RC2', Zhu Wen, 13 Mar 2023
Dear Reviewers,
Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits. We also appreciate your clear and detailed feedback and hope that the explanation has fully addressed all of your concerns.
Please see attachment for details.
Sincerely,
The Authors
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AC2: 'Reply on RC2', Zhu Wen, 13 Mar 2023
Wen Zhu et al.
Wen Zhu et al.
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