Effects of damage of Hatschek's pit of amphioxus on its structure and function

It is found for the first time that, after the structure and endocrine function of Hatschek’s pit of Bran-chiostoma belcheri are damaged by monosodium glu-tamate (MSG) treatment in breeding season, tbe ovulation of mature ovary, as well as the development of both ovary and testis of large-growth stage are obstructed and stagnated; and in non-breeding season, the process of gonadal development is delayed. The disturbed ovulation and gonadal development can definitely be restored with exogenous gonad-otropic hormone as the therapeutical substitute. These results may provide new proof for the complete understanding of the evolutional process of pituitary function in vertebrates and playing an important role in the reproductive endocrine control system of Hatschek’s pit of amphioxus.

Chinese Built-up Land in Floodplains Moving Closer to Freshwaters

Human proximity to water and its dynamics are important to understanding the socio-hydrological dilemma between using floodplains and avoiding flood risk.However,previous studies have not distinguished between the water proximity of built-up land in floodplains(BLF)and the water proximity of built-up land outside floodplains(BLOF).This article provides a new and spatiotemporal perspective of the BLF water proximities for understanding the changing flood risk in China.The results show that China’s BLFs had an average water proximity of 5.41 km in 2014.Most of the BLFs(62%,25.889103 km2)were located within 3 km of waterbodies.From 1990 to 2014,China’s BLFs increased rapidly by 81%from23.069103 km2 to 41.749103 km2,of which a large portion(57%)was concentrated in water surroundings(≤km),shortening the distance between BLFs and waterbodies by 169 m.The BLF growth concentrated in water surroundings even in areas where BLFs have an overall increasing distance from waterbodies.Both the increases in the BLFs and their proximity to waterbodies can increase flood exposure and exacerbate flood risk.The scientific community and policymakers should pay attention not only to the volume of BLF growth,but also its spatial relationship with waterbodies.

The Importance of Digital Elevation Model Selection in Flood Simulation and a Proposed Method to Reduce DEM Errors:A Case Study in Shanghai

Digital Elevation Models(DEMs)play a critical role in hydrologic and hydraulic modeling.Flood inundation mapping is highly dependent on the accuracy of DEMs.Various vertical differences exist among open access DEMs as they use various observation satellites and algorithms.The problem is particularly acute in small,flat coastal cities.Thus,it is necessary to assess the differences of the input of DEMs in flood simulation and to reduce anomalous errors of DEMs.In this study,we first conducted urban flood simulation in the Huangpu River Basin in Shanghai by using the LISFLOOD-FP hydrodynamic model and six open-access DEMs(SRTM,MERIT,CoastalDEM,GDEM,NASADEM,and AW3D30),and analyzed the differences in the results of the flood inundation simulations.Then,we processed the DEMs by using two statistically based methods and compared the results with those using the original DEMs.The results show that:(1)the flood inundation mappings using the six original DEMs are significantly different under the same simulation conditions—this indicates that only using a single DEM dataset may lead to bias of flood mapping and is not adequate for high confidence analysis of exposure and flood management;and(2)the accuracy of a DEM corrected by the Dixon criterion for predicting inundation extent is improved,in addition to reducing errors in extreme water depths—this indicates that the corrected datasets have some performance improvement in the accuracy of flood simulation.A freely available,accurate,high-resolution DEM is needed to support robust flood mapping.Flood-related researchers,practitioners,and other stakeholders should pay attention to the uncertainty caused by DEM quality.