This article describes the “Sao Francisco Floodplain Project” (SFFPP) aiming at defining a Mean Ordinary Flood Line (MOFL) on the banks of the Sao Francisco River, in East Central Brazil. Land inserted within the MOFL of large rivers in Brazil are characterized as government-owned and are ruled by a special legislation. The lack of consensus for an effective method for this delimitation has raised much conflicts between dwellers, land owners and the federal government. To solve this, the SFFPP first aims to determine the mean flood plain level using historical water level data and then find all the dates since the launch of the first satellite sensor with a 30 m resolution (Landsat-4, 1982) corresponding to these particular water levels with a small margin of error. All Landsat images corresponding to these dates were acquired to produce a delineation of the MOFL. In a thorough series of tests to extract the water surface, the K-means segmentation using the shortwave infrared band of Landsat yielded the best results. A first refining of the MOFL was performed by interpolating the Landsat bands to improve the smoothness of the waterline. This refinement reduced the average distance error between the Landsat water edge and the true water edge from 9 to 7.5 meters. Then, some sections of the MOFL was further completed or refined using high-resolution multi-source satellite images where available. These first results were very encouraging and we were able to acquire Landsat images for each section of the river corresponding to the mean flood water level. Because Brazil has been suffering a significant reduction in rainfall since 2013, no recent SAR or optical images such as Sentinel-1 and -2 could be used. Analysis of the water level time series confirmed an alarming decreasing trend in the water discharge of the Sao Francisco River.
Non-point source pollution (NPSP) is perhaps the leading cause of water quality problems and one of the most challenging environmental issues given the difficulty of modeling and controlling it. In this article, we applied the Manning equation, a hydraulic concept, to improve models of non-point source pollution and determine its influence as a function of slope - land cover roughness for runoff to reach the stream. In our study the equation is somewhat taken out of its usual context to be applies to the flow of an entire watershed. Here a digital elevation model (DEM) from the SRTM satellite was used to compute the slope and data from the RapidEye satellite constellation was used to produce a land cover map later transformed into a roughness surface. The methodology is applied to a 1433 km2 watershed in Southeast Brazil mostly covered by forest, pasture, urban and wetlands. The model was used to create slope buffer of varying width in which the proportions of land cover and roughness coefficient were obtained. Next we correlated these data, through regression, with four water quality parameters measured in situ: nitrate, phosphorous, faecal coliform and turbidity. We compare our results with the ones obtained by fixed buffer. It was found that slope buffer outperformed fixed buffer with higher coefficients of determination up to 15%.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.