Accuracy Of Topographic Data Research Articles

Numerical Simulation of Urban Inundation Processes and Their Hydraulic Quantities – Tsunami Analysis Hackathon Theme 1 –

The detailed understanding of tsunami hazard risk using numerical simulations requires a numerical model that can accurately predict tsunami inundation phenomena on land. In such models, the structural effects are indirectly considered using the variation of bottom roughness as a proxy for the differences in building densities. Only a few studies have conducted intermodel tests to investigate tsunami inundation in complex coastal urban cities. During the tsunami analysis hackathon held in September 2020, eight research groups met to have a detailed discussion on the current urban inundation problems. In this study, we conducted an intermodel comparison of the numerical tsunami models, using the data from physical experiments that were performed on a detailed urban model. Our objective was to investigate the necessary conditions of an accurate numerical model based that can ensure high reproducibility and practicality. It was confirmed that the accuracy of topographic data is an important parameter for tsunami inundation simulations in complex urban areas. Based on the computational cost and accuracy, we suggest that a resolution of 1 cm of topographic data is a sufficient condition for tsunami inundation simulations on 1/250 scale model.

Uncertainties in Tidally Adjusted Estimates of Sea Level Rise Flooding (Bathtub Model) for the Greater London

Sea-level rise (SLR) from global warming may have severe consequences for coastal cities, particularly when combined with predicted increases in the strength of tidal surges. Predicting the regional impact of SLR flooding is strongly dependent on the modelling approach and accuracy of topographic data. Here, the areas under risk of sea water flooding for London boroughs were quantified based on the projected SLR scenarios reported in Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (AR5) and UK climatic projections 2009 (UKCP09) using a tidally-adjusted bathtub modelling approach. Medium- to very high-resolution digital elevation models (DEMs) are used to evaluate inundation extents as well as uncertainties. Depending on the SLR scenario and DEMs used, it is estimated that 3%–8% of the area of Greater London could be inundated by 2100. The boroughs with the largest areas at risk of flooding are Newham, Southwark, and Greenwich. The differences in inundation areas estimated from a digital terrain model and a digital surface model are much greater than the root mean square error differences observed between the two data types, which may be attributed to processing levels. Flood models from SRTM data underestimate the inundation extent, so their results may not be reliable for constructing flood risk maps. This analysis provides a broad-scale estimate of the potential consequences of SLR and uncertainties in the DEM-based bathtub type flood inundation modelling for London boroughs.

하천범람 영역 자동생성 모델 및 표출 시스템 구현

본 논문의 목적은 1차원 수리모형인 HEC-RAS(Hydrologic Engineering Center's River Analysis System)를 통해 강우의 시간적 분포를 적용한 홍수위를 산정하고, 산정한 홍수위 값과 대상유역의 정밀한 지형데이터를 활용하여 홍수위에 따른 범람영역을 GIS기반의 사용자 정의 모델을 통해 자동 생성하는데 있다. 하천의 범람영역 분석은 지형데이터의 정확성에 따라 결과가 달라지므로 대상유역 지형 데이터의 정밀성이 최우선이다. 따라서 GIS기반의 홍수범람 영역을 자동생성하기 위해 UIS(Urban Information System)와 하천 관련 보고서, 수문학 정보 등을 기반으로 공간 및 속성 데이터의 구축방법을 제시하고, 대상 유역에 제시한 모델을 적용하여 GIS기반의 분석 결과를 표출시스템을 통해 제공한다. The goal of this paper is to calculate flood elevation by applying temporal distribution of rainfall through HEC-RAS(Hydrologic Engineering Center's River Analysis System) and to automatically create areas of flooding by a user-defined spatial model based on GIS using calculated values of flood elevation and detailed data of topography. Accuracy of topographic data is the most important factor because of deeply changing analysis results of flooding areas of a river. Therefore, this paper suggests a method of attributive and spatial data construction based on the GIS using UIS(Urban Information System, river-related reports, and hydrologic information. Also, we implement an expression system to provide analysis results extracted from the proposed model.