Satellite DEM Improvement Using Multispectral Imagery and an Artificial Neural Network

The digital elevation model (DEM) is crucial for various applications, such as land management and flood planning, as it reflects the actual topographic characteristic on the Earth’s surface. However, it is quite a challenge to acquire the high-quality DEM, as it is very time-consuming, costly, and often confidential. This paper explores a DEM improvement scheme using an artificial neural network (ANN) that could improve the German Aerospace’s TanDEM-X (12 m resolution). The ANN was first trained in Nice, France, with a high spatial resolution surveyed DEM (1 m) and then applied on a faraway city, Singapore, for validation. In the ANN training, Sentinel-2 and TanDEM-X data of the Nice area were used as the input data, while the ground truth observation data of Nice were used as the target data. The applicability of iTanDEM-X was finally conducted at a different site in Singapore. The trained iTanDEM-X shows a significant reduction in the root mean square error of 43.6% in Singapore. It was also found that the improvement for different land covers (e.g., vegetation and built-up areas) ranges from 20 to 65%. The paper also demonstrated the application of the trained ANN on Ho Chi Minh City, Vietnam, where the ground truth data are not available; for cases such as this, a visual comparison with Google satellite imagery was then utilized. The DEM from iTanDEM-X with 10 m resolution categorically shows much clearer land shapes (particularly the roads and buildings).

Study On Urban Rainstorm Pattern of Short-Duration Double-Peak

At present, researches on urban short-duration rainstorm patterns mainly focus on single-peak rainstorm patterns, and rarely involve double-peak rainstorm patterns, or convert double-peak patterns into single-peak patterns directly, even ignore the impact of double-peak patterns, which directly affects the urban flood planning and early warning and rescue. To scientifically and rationally deduce the urban short duration double-peak rain pattern, this paper proposes a new function fitting rain pattern method by constructing double-peak virtual rain peak rainfall and virtual rain peak coefficient (RPC), based on the idea of convert double-peak to singel-peak, then revert to the double-peak, directly deducing the double-peak rain pattern.The results show that (1) The rain pattern derived by the function fitting rain pattern method(FFRPM) can effectively improve the accuracy of the double-peak rain pattern, and is also more practical; (2) The fitting degree of function fitting rainfall pattern and actual rain pattern is more than 90%, accounting for 80%, the fitting degree of main and secondary peak rainfall is more than 90%, with an average of about 95%; the accuracy of the main and secondary peak positions is also relatively high; (3) Compared with the P&C rain pattern method(RPM), whether the overall accuracy or local peak rainfall, the FFRPM has the higher accuracy, especially more accurate on rain peak rainfall.

A state-based and optimal path dependant short-term flood planning

<p>Temporary flood protective defences (TFPD) are supplementary to permanent engineering solutions. In a flood event, asset managers are faced with a challenging task of deploying large-scale temporary defences at multiple locations. As the performance of temporary defences is sensitive to various uncertain weather condition factors, it is difficult to fix a single specific deployment plan as the optimal solution. This, moreover, leads to insufficient and/or underused defences on flood-affected locations. This paper describes a state-based (SB) mathematical modelling approach to deal with above challenge by adapting TFPD strategies consistently to short-term future as they unfold. We employ multistage stochastic and scenario tree to identify a set of alternative SB optimal paths for deployment planning. The proposed model is applied to nine flood-affected locations in Carlisle, northwest England. The results indicate that the inclusion of SB path-dependant solution strategy are beneficial for the flood asset manager faced with making short-term deployment planning decisions.</p>

How Public Managers Make Tradeoffs Regarding Lives: Evidence From a Flood Planning Survey Experiment

Public managers make decisions that may directly or indirectly affect the loss of human life, but there are few empirical analyses of whether and how public managers make tradeoffs among lives and other goods. We survey local government managers in the United States about tradeoffs using a vignette experiment with hypothetical flood scenarios. We find that managers make tradeoffs regarding lives saved compared with other features of the scenario, including project cost and property damage. Public works managers show a greater aversion to fatalities, while city managers and planners appear less averse. Our study also finds evidence of an equity preference.

How an adaptive and flexible short-term flood planning can be beneficial - a UK case study application

<p>Short term flood intervention planning includes identifying how the limited resources should be allocated to the most appropriate affected locations. The water level is an important factor for temporary flood protection planning for which adaptability of the plan to its changing future condition is regarded valuable. Moreover, flexibility in activation, delaying and replacement of the existing plans should be considered to mitigate the damages caused by future unknown condition. This research applies real options analysis which incorporates adaptability and flexibility in addressing “least-cost alternative”  location selection via multi-stage stochastic programming. We apply the proposed model to a case study in Eden catchment with nine different flood-affected cities with different degrees of uncertainty along Eden River in England. A multi-objective and mixed integer optimization model was formulated to solve on a scenario tree capable to choose most appropriate locations for deploying intervention measures of temporary flood protection. We examine the solution under various model parameters uncertainty and compare the results with the business as usual case presenting the benefits of proposed formulation in terms of expected damage and cost.</p>

Homogeneity in Patterns of Climate Extremes Between Two Cities—A Potential for Flood Planning in Relation to Climate Change

Information about potential scenarios and causes of floods is important for future planning. Historical weather data of Fredericton (New Brunswick) and Charlottetown (Prince Edward Island), the two coastal cities of Atlantic Canada, were analyzed using RClimDex, Mann–Kendall test, and Sen’s slope estimates for potential scenarios and causes of floods. Flood hazard analyses were conducted using GIS (Geographical Information System) and ArcSWAT software. The watersheds of Fredericton and Charlottetown were delineated from 25 × 25 m resolution DEMs (Digital Elevation Models) of the two cities followed by percent watershed area calculations for different elevation classes for flood generation. Over the past 100 years, there was a significant decreasing trend in the high intensity precipitation in Charlottetown supported by a significant decrease in the number of heavy precipitation days. However, maximum one-day precipitation and maximum five-day precipitation significantly increased in Charlottetown and Fredericton, respectively. Charlottetown received more annual precipitation than Fredericton. In the last 30 years, there was an event exceeding 50 mm precipitation (considered as a threshold for the return period of urban floods) in Charlottetown; Fredericton experienced such events for more than 1.5 times. For twelve times, these events occurred more than once in a year in Charlottetown as compared to fourteen times in Fredericton. Despite statistically proven similarities in the occurrence of extreme events in the two cities, the visualized flood hazards, and the mapping of watershed characteristics, no devastating floods were reported for Charlottetown. This does not necessarily mean that there had never been risks of flooding in Charlottetown. These findings may help policymakers for future developments.

The Use of a Microscale Physical Model to Simulate Bankfull Discharge in the Lower Reaches of the Yellow River

Microscale physical models (MSPMs) were once widely used in flood planning in large basins. They fell out of favor but are now being used again. This paper explores the benefits of using such a model for understanding a flood problem on the Lower Yellow River (LYR). We constructed an indoor MSPM of a nearly 800-km reach of the LYR. The model had different scales in the longitudinal, transverse, and vertical directions, and we adjusted the slope of the model. Meanwhile, a real-time water level monitoring system and an automatic flow control system were built on the MSPM to automatically control hydrodynamic testing. Through several discharge experiments, bankfull discharge for multiple MSPM sections was obtained and compared with measured data from the corresponding hydrological section of the prototype during the early flood season of 2016. The comparison demonstrated good linear correlation. The analysis of model similarity showed that although there was some deviation in gravity similarity between the MSPM and the prototype, the model discharge scale derived from resistance similarity adequately described the relationship between the model and the prototype bankfull discharge. Further analysis of the relationship between the model and the prototype bankfull discharge revealed that a split-line line may be better than a single regression line. A MSPM could reproduce the bankfull discharge of the LYR with the nearly 800-km reach in the laboratory which is impossible for a small distortion rate physical model, and obtain a result close to that of the assimilated numerical model.

ANALISA SISTEM JARINGAN DRAINASE (STUDI KASUS : DESA SUMENGKO, KECAMATAN SUKOMORO, KABUPATEN NGANJUK)

Drainage channels or flood control buildings are 12 general components of physical infrastructure that are useful to meet the needs of the community and are an important component of road support buildings. In the problem of flooding that occurred in some neighborhoods in the village of Sumengko, an analysis of the existing drainage channels is needed. This activity is expected to help solve flood problems in the area. The research method used is descriptive quantitative, the method of calculation, and translation of the results of field data processing. With this method, the research results obtained at 0.41 m3 / second for flood planning (Qr) using a rational formula for a 10-year period and 0.12 m3 / second for the capacity of the drainage channel (Qs). While the comparative requirements that meet are Qs≥Qr. So there needs to be an analysis of the drainage channel. From the analysis of the dimensions of the drainage channel, a new trapezoidal channel with a width of the bottom channel (b): 0.40 m; depth of waterlogged channel (h): 0.35 m; and guard height (w): 0.20 mSaluran drainase atau bangunan pengendali banjir merupakan 12 komponen umum fasilitas fisik insfrastruktur yang berguna untuk memenuhi kebutuhan masyarakat dan merupakan kompenen penting bangunan penunjang jalan. Dalam permasalahan banjir yang terjadi pada sebagian lingkungan Desa Sumengko diperlukan analisa terhadap saluran drainase eksisting. Kegiatan ini diharapkan dapat membantu menyelesaikan permasalahan banjir di daerah tersebut. Metode penelitian yang digunakandeskriptif kuantitatif, yaitu metode perhitungan dan penjabaran dari hasil pengolahan data lapangan. Dengan metode tersebut didapatkan hasil penelitian sebesar 0,41 m3/detik untuk debit banjir rencana (Qr) yang menggunakan rumus rasional untuk periode 10 tahunan dan 0,12 m3/detik untuk untuk kapasitas daya tampung saluran drainase (Qs). Sedangkan Syarat perbandingan yang memenuhi ialah Qs≥Qr. Sehingga perlu adanya analisa terhadap saluran drainase tersebut.Dari analisa dimensi saluran drainase yang dilakukan, menghasilkan saluran baru bentuk trapesium dengan lebar bawah saluran (b) : 0,40 m; kedalaman saluran yang tergenang air (h) : 0,35 m; dan tinggi jagaan (w) :0,20 m.

ANALISIS PENANGANAN BANJIR DI JATIMULYA KABUPATEN BEKASI JAWA BARAT

Jatimulya is a part of Bekasi Regency, which in the event of rain there will be a lot of puddles. The cause of inundation in the Jatimulya region is due to changes in the function of land from agriculture to settlements, problems with river drainage (3 rivers) due to narrowing of the flow due to bridges and siltation of rivers due to sedimentation and garbage.By calculating the Log Pearson III rain plan and calculating the discharge plan with a rational formula, it was determined that for the channel to be used for 50-year flood planning and the existing water building (bridges, culverts, siphons and box culverts) used 100-year flood planning.