Modelling Flood-Induced Wetland Connectivity and Impacts of Climate Change and Dam

Abstract

Hydrological connectivity between rivers and wetlands is considered one of the key critical factors for the integrity of floodplain landscapes. This study is a comprehensive modelling exercise on quantifying flood-induced wetland connectivity and the potential impacts of climate and water storage in an unregulated river basin in northern Australia. Flood inundation was simulated using a two-dimensional hydrodynamic model and the connectivities between wetlands and rivers were calculated using geoprocessing tools in ArcGIS. Wetlands in the floodplain were identified using waterbody maps derived from satellite imagery. A broadly representative sample of 20 wetlands were selected from 158 wetlands in the Mitchell basin considering location, size and spatial distribution. Five flood events ranging from 1 in 2 to 1 in 100 years were investigated to evaluate how connectivity changes with flood magnitude. Connectivities were assessed for the current condition as well as for two scenarios of future climate (Cwet and Cdry) and one scenario of dam storage. Results showed that a 1 in 100 years event inundated about 5450 km2 of land compared to 1160 km2 for a 1 in 2 years event. Average connectivity of wetlands in the Mitchell basin varies from 1 to 5 days for the floods of 1 in 2 to 1 in 26 years. As expected, a large flood produces longer duration of connectivity relative to a small flood. Results also showed that reduction in mean connectivity under a dryer climate (up to 1.8 days) is higher than the possibility of increase under a wet climate (up to 1 day). The impacts of a water storage, in the headwater catchment, are highly pronounced in terms of inundation and wetland connectivity (e.g., mean connectivity reduced by 1.7 days). The relative change in connectivity is higher for a small flood compared to that of a large event. These results demonstrate that there is a possibility of both increase and decease in connectivity under future climate. However, any water storage will negatively impact the connectivity between floodplain waterbodies and thus reduce the material exchange resulting in a reduction in primary and secondary productions in rivers and wetlands.

Dual-season comparison of OBIA and pixel-based approaches for coastal wetland classification

“…One indicator for monitoring wetland functioning is the extent of flooding in the form of pulses. The characterization of these fluctuations is the basis for understanding temporal limnological changes (Robinson et al, 2015;Liu et al, 2017;Karim et al, 2020). In the summer (dryer period), these areas are covered by wet meadows, a class that presented low accuracy for the producer and for the user, mainly in the pixel-based approach due to the spectral similarity with swamps and rice cultivation (Mahdavi et al, 2019).…”

Impact of river flow modification on wetland hydrological and morphological characters

“…Considering this, the present study also applied ML models for developing hydrological strength models using image-driven hydrological components. Since flood water is a reliable source of wetland, assessing flood extent over time and analyzing wetland within or beyond flood extent is also very useful (Greet et al, 2020;Karim et al, 2020). Flood simulation amongst is a reliable approach for this which is applied in this present case.…”

Analysis of water source contributions and their impacts on hydrological structural connectivity in plain urban river network areas based on stable isotopes (δ2H, δ18O)

“…The common methods include the index monitoring method (Liu et al, 2020), graph theory method (Zhang et al, 2022), connected function method (Nguyen et al, 2021), hydrological model method (Li, Zhang, et al, 2019b), comprehensive index method (Li et al, 2018) and so on. For example, Karim et al (2020) used the MIKE21 model to evaluate the degree of connectivity between wetlands and rivers. Lesack and Marsh (2010) judged the connectivity between rivers and lakes by monitoring the duration of the river water level exceeding the overflow weir.…”