Estimating Floodwater Depths from Flood Inundation Maps and Topography

Information on flood inundation extent is important for understanding societal exposure, water storage volumes, flood wave attenuation, future flood hazard, and other variables. A number of organizations now provide flood inundation maps based on satellite remote sensing. These data products can efficiently and accurately provide the areal extent of a flood event, but do not provide floodwater depth, an important attribute for first responders and damage assessment. Here we present a new methodology and a GIS‐based tool, the Floodwater Depth Estimation Tool (FwDET), for estimating floodwater depth based solely on an inundation map and a digital elevation model (DEM). We compare the FwDET results against water depth maps derived from hydraulic simulation of two flood events, a large‐scale event for which we use medium resolution input layer (10 m) and a small‐scale event for which we use a high‐resolution (LiDAR; 1 m) input. Further testing is performed for two inundation maps with a number of challenging features that include a narrow valley, a large reservoir, and an urban setting. The results show FwDET can accurately calculate floodwater depth for diverse flooding scenarios but also leads to considerable bias in locations where the inundation extent does not align well with the DEM. In these locations, manual adjustment or higher spatial resolution input is required.     

Millennium Consumption Goals (MCGs) for Rio+20 and beyond: A practical step towards global sustainability

In January 2011, the idea of Millennium Consumption Goals (MCGs) was first proposed at the United Nations, because unsustainable patterns of consumption and production have led to multiple problems threatening the future of humanity. The global economy driven by consumption already uses natural resources equivalent to almost 1.5 planets earth, with the world's richest 1.4 billion consuming almost 85% of global output, which is over 60 fold the consumption of the poorest 1.4 billion. The consumption of the rich is not only ecologically unsustainable, but also “crowding out” the prospects of the poor and exacerbating inequalities that increase the risk of conflict and global unrest. The MCGs provide an innovative future vision and complement the Millennium Development Goals (MDGs) that aim to help the world's poor. First, the MCGs seek to address the issues of global poverty and inequality by ensuring that the basic consumption needs of over 2 billion poor people are met. Next, the MCGs will provide benchmarks for the consumption of the rich, which will reduce the burden on the world's natural resource base. Instead of viewing the affluent as a problem, the novel approach of the MCGs would persuade them to contribute to the solution without having to reduce their quality of life. The MCGs apply even‐handedly to the rich in all countries. The concept enjoys broad support worldwide and is being promoted by a global coalition called the MCG Initiative (MCGI). A bottom‐up approach has already been started by many pioneering individuals, communities, organizations, firms, cities, regions and nations. They prefer not to wait for broad multilateral agreements and are acting now, to voluntarily pursue their own specific MCGs. A parallel top‐down path is being pursued through mandatory agreements at the United Nations/international level, starting with the Rio+20 Earth Summit and beyond. The MCGs fit in with other major UN initiatives like Agenda 21, the MDGs, green economy, SCP and the Sustainable Development Goals.     

Comparative Analysis of Inundation Mapping Approaches for the 2016 Flood in the Brazos River,Texas

Accurate and timely flood inundation maps serve as crucial information for hydrologists, first‐responders, and decision makers of natural disaster management agencies. In this study, two modeling approaches are applied to estimate the inundation area for a large flooding event that occurred in May 2016 in the Brazos River: (1) Height Above the Nearest Drainage combined with National Hydrograph Dataset Plus (NHDPlus‐HAND) and (2) International River Interface Cooperative — Flow and Sediment Transport with Morphological Evolution of Channels (iRIC‐FaSTMECH). The inundation extents simulated from these two modeling approaches are then compared against the observed inundation extents derived from a Landsat 8 satellite image. The simulated results from NHDPlus‐HAND and iRIC‐FaSTMECH show 56% and 70% of overlaps with the observed flood extents, respectively. A modified version of the NHDPlus‐HAND model, considering networked catchment behaviors, is also tested with an improved fitness of 67%. This study suggests that NHDPlus‐HAND has the potential for real‐time continental inundation forecast due to its low computational cost and ease to couple with the National Water Model. Better performance of NHDPlus‐HAND can be achieved by considering the inter‐catchment flows during extreme riverine flood events. Overall, this study presents a comprehensive examination made of remote sensing compared with HAND‐based inundation mapping in a region of complex topography.     

Groundwater resource management and environmental protection

Population and economic developmental pressures will continue to put increasing pressure on the environment, especially on scarce water resources. Meanwhile, large numbers of poor families in the developing countries still lack access to safe water. An integrated water resource planning and policy analysis framework is presented that permits the main issues and alternative options to be systematically considered and prioritized, especially problems arising from groundwater pollution. Basic principles of water resource economics are used to illustrate how the neglect of long-term environmental considerations jeopardizes the availability and quality of groundwater resources in the Greater Manila area. This paper contains a brief overview of drinking water and sanitation issues in developing countries, presents a policy-oriented analysis of a groundwater problem of great relevance worldwide, and demonstrates how the study conclusions might be implemented practically in a constrained developing country context.     

The pricing of water services in developing countries

This paper focuses on improving efficiency in the water and sewerage sectors through long-run marginal cost pricing, adjusted for financial needs, externalities, second best considerations, lifeline tariffs and cross subsidization within an integrated water resource planning (IWRP) framework. Supply efficiency suggests that for a given price structure, an optimal long-run investment plan and a corresponding level of supply quality should be determined which maximizes net social benefits. Supply efficiency also requires efficient operation of the water system, including optimization of losses.     

Water supply policies and issues in developing countries

The significant progress made during the UN International Water Decade is reviewed, eight years after its inception in 1981. Major issues remain, especially in rural areas. The advantages of an integrated water resource planning framework (IWRP) are explained, including the use of this process to develop a flexible strategy for the water and sewerage sector to meet national policy objectives. Economic efficiency in supply implies optimal service quality and least cost planning, while efficient pricing policy requires the implementation of long-run marginal cost based tariffs. Better sector organization, management, accountability, options for decentralization and innovative financing methods are also discussed.     

Intercomparison of Satellite Remote Sensing‐Based Flood Inundation Mapping Techniques

The objective of this study was to determine the accuracy of five different digital image processing techniques to map flood inundation extent with Landsat 8–Operational Land Imager satellite imagery. The May 2016 flooding event in the Hempstead region of the Brazos River, Texas is used as a case study for this first comprehensive comparison of classification techniques of its kind. Five flood water classification techniques (i.e., supervised classification, unsupervised classification, delta‐cue change detection, Normalized Difference Water Index [NDWI], modified NDWI [MNDWI]) were implemented to characterize flooded regions. To identify flood water obscured by cloud cover, a digital elevation model (DEM)–based approach was employed. Classified floods were compared using an Advanced Fitness Index to a “reference flood map” created based on manual digitization, as well as other data sources, using the same satellite image. Supervised classification yielded the highest accuracy of 86.4%, while unsupervised, MNDWI, and NDWI closely followed at 79.6%, 77.3%, and 77.1%, respectively. Delta‐cue change detection yielded the lowest accuracy with 70.1%. Thus, supervised classification is recommended for flood water classification and inundation map generation under these settings. The DEM‐based approach used to identify cloud‐obscured flood water pixels was found reliable and easy to apply. It is therefore recommended for regions with relatively flat topography.