Multi-criteria decision based geospatial mapping of flood susceptibility and temporal hydro-geomorphic changes in the Subarnarekha basin, India

The Subarnarekha River in east India experiences frequent high magnitude flooding in monsoon season.In this study,we present an in-depth analysis of flood hydrology and GIS-based flood susceptibility mapping of the entire catchment.About 40 years of annual peak discharge data,historical cross-sections of different gauging sites,and 12 flood conditioning factors were considered.Our flood susceptibility mapping followed an expert knowledge-based multi-parametric analytical hierarchy process(AHP)and optimized AHP-VIP methods.Peak hydrology data indicated more than 5 times higher discharge contrasted with the mean streamflow of the peak monsoon month in all hydro-monitoring stations that correspond to possible overbank flooding in the shallow semi-alluvial reaches of the Subarnarekha River.Widthdepth ratio revealed continuous changes on the channel cross-sections at decadal scale in all gauging sites.Predicted flood susceptibility map through optimized AHP-VIP method showed a great amount of areas(38%)have a high probability of flooding and demands earnest attention of administrative bodies.The AHP-VIP based flood susceptibility map was theoritically validated through AUC approach and it showed fairly high accuracy(AUC=0.93).Our study offers an exceptionally cost and time effective solution to the flooding issues in the Subarnarekha basin.

A New Foraminiferal Bioindicator for Long-Term Heat Stress on Coral Reefs

Coral reefs are in terminal decline.For conservation to be effective,naturally depauperate reefs must be distinguished from those recently degraded by humans.Traditional reef monitoring is time consuming and lacks the longevity to make this distinction.Success in using foraminifera as bioindicators for reef health has hitherto levered their response to nutrients.Because ocean heat waves are the dominant driver of coral bleaching and death,there is compelling motivation to develop new foraminiferal bioindicators that inform on temperature stress over meaningful timescales.This study focuses on identifying which foraminifera respond systematically to the temperature stress that kills corals.Statistical models were used to compare endosymbiont-bearing foraminiferal families,collected along a heat-stress gradient spanning the Solomon Islands and New Caledonia,to live coral cover at the same sites.Results indicate that Amphisteginidae foraminifera and coral cover show a significant decline in abundance as heat stress increases along the transect sites.Furthermore,ocean productivity and salinity,both recognized environmental influences on foraminifera,are shown to be subordinate to temperature in their sway of this ecological patterning.These findings indicate the potential for using foraminifera to develop new indices capable of quantifying long-term thermal impacts on reefs.