A Combined Field and Remote-Sensing Based Methodology to Assess the Ecosystem Service Potential of Urban Rivers in Developing Countries

Abstract

Natural rivers in urban areas bear significant potential to provide ecosystem services for the surrounding inhabitants. However, surface sealing by houses and street networks, urban drainage, disposal of waste and wastewater resulting from advancing urbanization usually lead to the deterioration of urban rivers and their riparian areas. This ultimately damages their ability to provide ecosystem services. This paper presents an innovative methodology for a rapid and low-cost assessment of the ecological status of urban rivers and riparian areas in developing countries under data scarce conditions. The methodology uses a combination of field data and freely available high-resolution satellite images to assess three ecological status categories: river hydromorphology, water quality, and riparian land cover. The focus here is on the assessment of proxies for biophysical structures and processes representing ecological functioning that enable urban rivers and riparian areas to provide ecosystem services. These proxies represent a combination of remote sensing land cover- and field-based indicators. Finally, the three ecological status categories are combined to quantify the potential of different river sections to provide regulating ecosystem services. The development and application of the methodology is demonstrated and visualized for each 100 m section of the Pochote River in the City of León, Nicaragua. This spatially distributed information of the ecosystem service potential of individual sections of the urban river and riparian areas can serve as important information for decision making regarding the protection, future use, and city development of these areas, as well as the targeted and tailor-made development of nature-based solutions such as green infrastructure.

A Conceptual Approach to Modeling the Geospatial Impact of Typical Urban Threats on the Habitat Quality of River Corridors

“…The natural wells deliver significant amounts of clean water to the river even during the dry season from November to April, when the main river is fed only by wastewater from households. The contribution from natural wells leads to an important dilution of wastewater, and together with the natural morphology of the river, this results in a continuous improvement of the water quality downstream [4].…”

“…The negative impact of the pollution on the river, which originates from both poorly performing wastewater treatment plants and illegal direct wastewater discharges, also negatively impacts on riparian habitats. According to a previous study from Beißler and Hack [4], water pollution can be categorized into four different degrees of pollution: seasonally polluted, polluted, seasonally highly polluted, and highly polluted (see Figure 2 for the spatial distribution of water pollution per 100 m river sections and Table for the threat parameterization).…”

“…Using more land cover classes would allow for a more nuanced description of the spatial distribution of habitat suitability. Our land cover, i.e., habitat suitability input, was based on a land-use classification of a satellite image [4] with only punctual validation using ground truth information. Using this methodology, a further classification of land-use classes, such as irrigated and rain-fed agriculture, as well as a consideration of bare soil, would be possible.…”

“…More ground truth information could help to identify larger patches with higher suitability scores and smaller patches with lower scores. If more ground truth information is available, a more sophisticated LULC classification, similar to the one proposed by Chapa et al [4], could be useful for distinguishing additional habitat types and suitabilities.…”

“…Since there is a significant need to drain excess stormwater and to discharge wastewater from urban areas, rivers are used as receiving water bodies due to their topography [3]. However, when rivers are excessively used for stormwater and wastewater drainage (especially when the drained waters are not or not sufficiently treated), other functions of a river corridor (e.g., recreational and ecological functions) are lost [4,5]. It is important to create awareness regarding the potential of rivers to provide ecosystem services before they are completely lost.…”