Effect of channel morphological changes on wetland transformation.

Keeping aside the traditional approaches to investigating floodplain wetland transformation, the current study investigated various aspects of it through changes in river channel morphology and drainage pattern. The study analyzed wetland transformation using satellite image-based machine learning and intensive fieldwork. Ordinary Least Square (OLS) regression was applied to identify dominant influencing factors among 24 contributing factors under six clusters to eight dependent phenomena of transformation. The result showed that 57 % of wetland area lost since 1991, and existing wetland has also experiencing hydrological scarcity. From 1991 to 2021, the area under low water depth (<1 m.) inflated from 18.55 % to 50.54 %, the hydro-period narrowed down, and the appearance of water become inconsistent. The OLS result showed that changes in channel morphology (bottle neck channel, embankment-driven carrying capacity enhancement, etc.), interruptions in river and wetland connecting channels (source closure, breaching the continuity, conversion in to agricultural land, etc.), and changes in flood ambience (regulated by dam construction, erection of embankments, etc.) majorly contributed to wetland transformation. Very high explainability was found in the cases of rate of wetland loss, decreasing water depth under greater depth, narrowing hydro-period (R2 > 0.9). The findings of this work would be a good policy document for floodplain wetland management.

How hydrological components of urban blue space influence the thermal milieu?

Present study examines the possible improvement of thermal discomfort mitigation. Unlike prior researches, which focused primarily on cooling effects of urban blue space, this study, instead of physical presence of blue space considers its hydrological components. The aim of the study is to better understand the role hydrological components like water consistency depth etc. In temperature regulation. The work uses field surveys and modeling to demonstrate how these hydrological factors influence the cooling effect of blue space, providing insights on urban thermal management. To fulfill the purpose, spatial association of hydrological components blue space with its thermal environment and cooling effects was assessed. The control of hydrological components on the surrounding air temperature was examined by conducting case studies. RESULTS: reveals greater hydro-duration, deeper water, and higher Water Presence Frequency (WPF) produce greater cooling effects. The study demonstrates a favorable correlation between hydrological richness and temperature reduction. The study also analyzes how land use and wetland size affect temperature, emphasizing the significance of hydrological conservation and restoration for successful temperature mitigation. Due to their hydrology, larger wetlands are able to moderate temperature to some extent, whereas smaller, fragmented wetlands being hydrologically poor are not so influential in this regard. With these results, the present study reaches beyond to the general understanding regarding the cooling effects of the urban blue spaces. While the previous studies primarily focused on estimating the cooling effect of urban blue space, the current one shows its synchronization with the hydrological characteristics. Novelty also entrusts here, through the modeling and field survey current study demonstrates deeper and consistent water coverage in the urban blue space for maximum period of a year pronounces the cooling effect. In addition, in this cooling effect, the role of land use which is a strong determinant of many aspects of the urban environment is also highlighted. Since all these findings define specific hydrological feature, the study has several practical implications. Mare restoration of urban blue space is not enough to mitigate the thermal discomfort. In order to optimize the cooling effect, the conservation of the hydrological richness is essential. The hydrological richness of the smaller wetlands and the edge of the larger wetlands is to be improved. The connection of these wetlands with the adjacent mighty may strengthen the hydrology. The vegetation was found to promote the cooling effect whereas shorter building helped in spreading the cooling effect. Such finding drives to incorporate the blue space with the green infrastructure along with restricting the building height atleast at the edge of the blue space.

Resolution effects on ox-bow lake mapping and inundation consistency analysis in moribund deltaic flood plain of India.

Research on investigating spatial resolution effect on image-based wetland mapping was done, and reported finer resolution is more appropriate. But is Sentinel image more effective than Landsat image for delineating ox-bow lake, a cut-off channel of a river, and for mapping inundation frequency? Inundation frequency means regularly, water appears in a pixel. In order to obtain these answers, the present study used frequently used spectral indices like normalized difference water index (NDWI), modified NDWI (MNDWI), re-modified NDWI (RmNDWI) and ensemble vegetation inclusive aggregated water index (ViAWI). For obtaining inundation consistency character, the water presence frequency (WPF) approach was adopted. A set of accuracy matrices was applied for validating the resolution effect. Results revealed that among the used indices, MNDWI was found suitable for ox-bow lake mapping. But this index is not able to map vegetated part of the ox-bow lakes. This problem was resolved using ensemble ViAWI. Inundation frequency analysis exhibited that about 70% of the area is consistent with water presence and therefore is hydro-ecologically and economically viable, and no such major differences were recorded between Sentinel and Landsat images. The study further revealed that finer resolution Sentinel images are more effective in ox-bow lake mapping and characterising inundation frequency, but they were not significantly better. Accuracy difference between them was found at the very minimum. Therefore, the study recommended that in a Sentinel image sparse condition, Landsat images could alternatively be used without much accuracy departure, particularly on those water bodies where water appearance is not highly erratic.