had magnitude of 9.0 on the Richter Scale with the epicenter approximately 70 km east of the Oshika Peninsula in Miyagi Prefecture. This earthquake triggered terrible tsunami waves which hit the coast of Japan and propagated around the Pacific Ocean. The earthquake and tsunami caused extensive and severe infrastructural damage, such as damages of coastal protection structures and buildings, and significantly changed coastal and river morphology. This paper presents tsunami-induced coastal and estuarine morphology changes in Miyagi Prefecture, Japan, and subsequent recovery process in each study area. On sandy coasts, discontinuous coastal protection is likely to be severely damaged, resulting in serious erosion in the surrounding sandy coast. Furthermore, severe breaching was observed on sandy coasts where formerly river mouth was located, due to strong return flow from the catchment area. The restoration process of the coast and estuaries is highly dependent on sediment supply availability in the surrounding area. Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. H. Tanaka et al. 1250010-2 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. Coastal and Estuarine Morphology Changes 1250010-3 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. 1250010-5 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. 1250010-6 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. Coastal and Estuarine Morphology Changes 1250010-16 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. 1250010-19 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. 1250010-23 Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 08/23/15. For personal use only. H. Tanaka et al.
In this study, we projected the future beach loss in Japan's 77 coastal zones due to sea-level rise (SLR) based on representative concentration pathway (RCP) scenarios and 21 models of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The beach-loss curve for SLR in Japan was constructed, and uncertainties associated with SLR projections and sediment sizes were evaluated. Beach-loss rates in the future (2081-2100) were projected to be 62% for the ensemble mean RCP2.6 scenario, 71% for RCP4.5, 73% for RCP6.0, and 83% for RCP8.5, and the rates projected by the CMIP5 models for RCP4.5 ranged widely from 61% to 87%. The effect of the spatial distribution of SLR in each CMIP5 model on beachloss rate in Japan is insignificant, while the effects of differences in the SLR values among RCP scenario and CMIP5 models are significant. The maximum uncertainties associated with sediment sizes (0.2--Q.6 mm) against the same SLR were assessed to be 38%. Despite significant uncertainties in the projected beach loss, results in the near future (2046--2065) reveal that the beach-loss rates between 18% and 79% differed by 60% in the near future and between 28% and 96% differed by 70% in the future. For the worst case scenario in the near future, the projected beach width is less than 10m in more than half of the 77 coastal zones, which would cause serious damage to coastal structures such as seawalls and revetments in beach areas. Thus, the development of effective measures to combat beach loss is critical for Japan's coastal management.
[1] Field observations were conducted on a natural, open ocean beach system in Japan to investigate characteristics of wind-blown sand transport under various weather conditions including a storm event. Data sets over periods of several hours included blown sand impact counts, three-dimensional wind conditions, hourly precipitation, and moisture content of the sediment surface. The intermittent blown sand impact data shifted by 1 s ahead of the wind velocity correlated with the wind velocity during a no-rainfall period (for an assumed dry surface) and in the longshore wind direction (for sufficiently long fetch length). The 5-min mean wind velocity/impact counts relationship was well constrained by both second-and third-order polynomial fitting of velocity under similar weather conditions. During a no-rainfall period and in the longshore wind direction, the relationship between the wind velocity and sand flux estimated from the counts coincides with existing studies in wind tunnel experiments. The sand flux, however, decreased by 1 order of magnitude because of a change in the wind direction from longshore to cross-shore and then by more than 1 order of magnitude because of an increase in the moisture content. Threshold wind velocity calculated using the time fraction equivalence method with the impact counts and the horizontal wind velocity in 5-min sampling periods was approximately equal to the value predicted using Bagnold's equation during the no-rainfall period and increased significantly during the rainfall phase. The sand flux sensor has several limitations for complex conditions in the field; however, it provides a number of characteristics of sand transport under various meteorological conditions.
At 14:46 JST on March 11, 2011 a magnitude 9.0 earthquake (2011 Tohoku Earthquake and Tsunami) occurred off the Pacific Coast of Miyagi Prefecture. This study investigated the extensive changes in beach morphology due to the earthquake and tsunami along the 15 km Northern Sendai Coast using remotely sensed data. The remote sensing analysis on the beach topography and coastal forest demonstrated the following notable characteristics of beach morphological change: erosion of the northern barrier at the mouths of the Nanakitagawa and Natorigawa Rivers; erosion at an old river channel; scour landward of the seawalls in the longshore direction; erosion and deposition in beach areas with detached breakwaters; and deposition in coastal forest areas. Linkage of the deposition in the forest areas with the damage type of coastal forests was observed. The impact of the 1250009-1Coast. Eng. J. 2012.54. Downloaded from www.worldscientific.com by UNIVERSITY OF QUEENSLAND on 08/16/15. For personal use only. K. Udo et al.earthquake and tsunami on the beach morphology was serious; roughly 60% of the study area was degraded by 0.2-0.5 m in elevation mainly due to land subsidence, and a total of 0.4 km 2 of beach area was eroded mainly due to erosion of the northern barrier at the mouths of the Nanakitagawa and Natorigawa Rivers. This study explores the geographical changes brought on by a tremendous earthquake and tsunami, which will help to elucidate the mechanisms of coastal forest destruction, beach erosion, and their interaction during tsunami events.
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Downscaling global weather prediction model outputs to individual locations or local scales is a common practice for operational weather forecast in order to correct the model outputs at subgrid scales. This paper presents an empirical-statistical downscaling method for precipitation prediction which uses a feed-forward multilayer perceptron (MLP) neural network. The MLP architecture was optimized by considering physical bases that determine the circulation of atmospheric variables. Downscaled precipitation was then used as inputs to the super tank model (runoff model) for flood prediction. The case study was conducted for the Thu Bon River Basin, located in Central Vietnam. Study results showed that the precipitation predicted by MLP outperformed that directly obtained from model outputs or downscaled using multiple linear regression. Consequently, flood forecast based on the downscaled precipitation was very encouraging. It has demonstrated as a robust technology, simple to implement, reliable, and universal application for flood prediction through the combination of downscaling model and super tank model.
This paper presents an assessment of the changes in future floods. The ranked area-average heavy daily rainfall amounts simulated by a super-high-resolution (20 km mesh) global climate model output are corrected with consideration of the effects of the topography on heavy rainfall patterns and used as a basis to model design storm hyetographs. The rainfall data are then used as the input for a nearly calibration-free parameter rainfall–runoff model to simulate floods in the future climate (2075–2099) at the Upper Thu Bon River basin in Central Vietnam. The results show that although the future mean annual rainfall will not be considerably different compared to the present-day climate (1979–2003), extreme rainfall is projected to increase vigorously, leading to a similar order of intensification of future floods. It is very likely that the flood peak with a 25-year recurrence will increase approximately 42% relative to the present-day climate. The occurrence of floods with a 10-year recurrence may exceed those with a 25-year recurrence in the present-day climate. The projection results also exhibit insignificant uncertainties caused by an artificial neural network-based bias correction model. Additionally, the presented bias correction model shows advantages over a simple climatology scaling method.
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