Using Rapid Repeat SAR Interferometry to Improve Hydrodynamic Models of Flood Propagation in Coastal Wetlands

2021 ◽  
pp. 104088
Author(s):  
Xiaohe Zhang ◽  
Cathleen E. Jones ◽  
Talib Oliver Cabrera ◽  
Marc Simard ◽  
Sergio Fagherazzi
2021 ◽  
Author(s):  
Sergio Fagherazzi ◽  
Xiaohe Zhang ◽  
Cathleen Jones ◽  
Talib Oliver-Cabrera ◽  
Marc Simard

<p>The propagation of tides and riverine floodwater in coastal wetlands is controlled by subtle topographic differences and a thick vegetation canopy. A precise quantification of fluxes of water, sediments and nutrients is crucial to determine the resilience and vulnerability of coastal wetlands to sea level rise. High-resolution numerical models have been used in recent years to simulate fluxes across wetlands. However, these models are based on sparse field data that can lead to unreliable results. Here, we utilize high spatial-resolution, rapid repeat interferometric data from the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) to provide a synoptic measurement of sub-canopy water-level change resulting from tide propagation into wetlands.  These data are used to constrain crucial model parameters and improve the performance and realism of simulations of the Wax Lake wetlands in coastal Louisiana (USA). A sensitivity analysis shows that the boundary condition of river discharge should be calibrated first, followed by iterative correction of terrain elevation. The calibration of bed friction becomes important only with the boundary and topography calibrated. With the model parameters calibrated, the overall Nash-Sutcliffe model efficiency for water-level change increases from 0.15 to 0.53 with the RMSE reduced by 26%. More importantly, constraining model simulations with UAVSAR observations drives iterative modifications of the original Digital Terrain Model. In areas with dense wetland grasses, the LiDAR signal is unable to reach the soil surface, but the L-band UAVSAR instrument detects changes in water levels that can be used to infer the true ground elevation. The high spatial resolution and repeat-acquisition frequency (minutes to hours) observations provided by UAVSAR represent a groundbreaking opportunity for a deeper understanding of the complex hydrodynamics of coastal wetlands.</p>


2021 ◽  
Author(s):  
Tom Fairchild ◽  
William Bennett ◽  
Greg Smith ◽  
Brett Day ◽  
Martin Skov ◽  
...  

Abstract As storm-driven coastal flooding increases under climate change, wetlands such as saltmarshes are held as a nature-based solution. Yet evidence supporting wetlands’ storm protection role in estuaries - where both waves and upstream surge drive coastal flooding - remains scarce. Here we address this gap using numerical hydrodynamic models within eight contextually diverse estuaries, simulating storms of varying intensity and coupling flood predictions to damage valuation. Saltmarshes reduced flooding across all studied estuaries and particularly for the largest – 100-year – storms, for which they mitigated average flood extents by 35% and damages by 37% ($8.4M). Across all storm scenarios, wetlands delivered mean annual damage savings of $2.7M per estuary, exceeding annualised values of better-studied wetland services such as carbon storage. Spatial decomposition of processes revealed flood mitigation arose from both localised wave attenuation and estuary-scale surge attenuation, with the latter process dominating: mean flood reductions were 17% in the sheltered top third of estuaries, compared to 8% near wave-exposed estuary mouths. Saltmarshes therefore play a generalised role in mitigating storm flooding and associated costs in estuaries via multi-scale processes. Ecosystem service modelling must integrate processes operating across scales or risk grossly underestimating the value of nature-based solutions to the growing threat of storm-driven coastal flooding.


Author(s):  
Dipayan Dey ◽  
Dipayan Dey ◽  
Ashoka Maity ◽  
Ashoka Maity

Algae has a great potential for quick capture of biological carbon and its storage in saltwater-inundated coastal wetlands and can also be introduced as a climate adaptive alternate farming practice. An intervention with native algal flora Enteromorpha sp. in enclosed coastal Sundarbans in India on two open water culture techniques, viz. U-Lock & Fish-Bone, shows that growth in native algal stock is influenced by seasonal variations of salinity and other limnological factors. Sundarbans, facing the odds of climate change is fast loosing arable lands to sea level rise. Algaculture in inundated coastal areas can be an adaptive mitigation for the same. Perusal of results show that daily growth rate (DGR%) increases with increasing salinity of the intruding tidal waters to an extent and biomass increment under salt stress results in accumulation of metabolites those are having nutrient values and can yield bio-diesel as well. Algal growth recorded mostly in post monsoon period, has impacts on pH and Dissolved Oxygen (DO) of the ambient water to facilitate integrated pisciculture. The paper suggests that alga-culture has unrealized potentials in carbon sequestration and can be significantly used for extraction of Biodiesel.


1999 ◽  
Vol 45 (151) ◽  
pp. 533-538 ◽  
Author(s):  
Niels Reeh ◽  
Søren Nørvang Madsen ◽  
Johan Jakob Mohr

AbstractUntil now, an assumption of surface-parallel glacier flow has been used to express the vertical velocity component in terms of the horizontal velocity vector, permitting all three velocity components to be determined from synthetic aperture radar interferometry. We discuss this assumption, which neglects the influence of the local mass balance and a possible contribution to the vertical velocity arising if the glacier is not in steady state. We find that the mass-balance contribution to the vertical surface velocity is not always negligible as compared to the surface-slope contribution. Moreover, the vertical velocity contribution arising if the ice sheet is not in steady state can be significant. We apply the principle of mass conservation to derive an equation relating the vertical surface velocity to the horizontal velocity vector. This equation, valid for both steady-state and non-steady-state conditions, depends on the ice-thickness distribution. Replacing the surface-parallel-flow assumption with a correct relationship between the surface velocity components requires knowledge of additional quantities such as surface mass balance or ice thickness.


2007 ◽  
Vol 2 (1) ◽  
Author(s):  
M. Hochedlinger ◽  
W. Sprung ◽  
H. Kainz ◽  
K. König

The simulation of combined sewer overflow volumes and loads is important for the assessment of the overflow and overflow load to the receiving water to predict the hydraulic or the pollution impact. Hydrodynamic models are very data-intensive and time-consuming for long-term quality modelling. Hence, for long-term modelling, hydrological models are used to predict the storm flow in a fast way. However, in most cases, a constant rain intensity is used as load for the simulation, but in practice even for small catchments rain occurs in rain cells, which are not constant over the whole catchment area. This paper presents the results of quality modelling considering moving storms depending on the rain cell velocity and its moving direction. Additionally, tipping bucket gauge failures and different corrections are also taken into account. The results evidence the importance of these considerations for precipitation due the effects on overflow load and show the difference up to 28% of corrected and uncorrected data and of moving rain cells instead of constant raining intensities.


2020 ◽  
Author(s):  
Dorothy Peteet ◽  
◽  
Molly Dunton ◽  
Molly Dunton ◽  
Carol Wang-Mondaca ◽  
...  
Keyword(s):  

Ecohydrology ◽  
2011 ◽  
Vol 4 (4) ◽  
pp. 597-607 ◽  
Author(s):  
V. Marconi ◽  
M. Antonellini ◽  
E. Balugani ◽  
E. Dinelli

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