Remote Sensing and (GIS) applications in the Erosion studies at the Romero river Watershed
Figure 7. Slope length map of water shed.
Figure 7 is the slope Length Map of the watershed based on topographic and slope maps.
Figure 8 Estimated soil loss (tons/hectare/year)
Figure 8 is the Estimated Soil Loss Map. The estimated soil loss due to erosion is about 5 to 10 tons/ hectare /year. However, there are isolated areas that are suffering from severe erosion problems, with much as 100 to 1,000 tons/ hectare/year of soil loss.
Figure 9. Estimated soil erosion depth (centimeters/10years) of the watershed.
Figure 9 is the Estimated Soil Erosion Depth Map. Converting the volume of soil loss into erosion depth (centimeters) for a ten year period, the whole watershed, on the average is not critically subjected to severe erosion hazard. Calculations shows that on the average, about 0.1 - 1 cm. Of topsoil can be lost due to erosion in ten years. This can be considered part of the natural soil renewal process. It can be noted that the GIS map identified critical areas where soil conservation is neede most. These are the areas where soil depth loss amount to 50 - 200 centimeters per ten years.
Summary and Conclusion
The following maps were prepared through GIS and remote sensing techniques as part of the development of geospatial database for the Romero River Watershed using TNT Map and image Processing System, PC ARCVIEW, and Fortran: (1) four thematic maps (topographic, land use, soil, slope), (2) three derived maps (land cover, slope length, soil productivity), and (3) two simulation model maps (soil loss in tons/ha/year and erosion depth in centimeters/10 years).
The computer-generated maps reveal critical areas of concern. Considering the Landsat image of the watershed vis-à-vis the depth of erosion estimates for the next ten years, it can be concluded that although agriculture is the dominant land use, the watershed analysis projected a minimal soil depth loss.
The combined GIS and remote sensing technology is an excellent tool for monitoring, land degradation, land use changes as well as soil and water resource changes over time.
In addition to the geospatial database report presentation and erosion studies, soil productivity studies as component of watershed analysis is being conducted to evaluate the soil dynamics. Figure 10 is the current Soil Productivity Capability Classification Rating Map of the watershed. The soil productivity rating of the different soil mapping units showed that in the lowlands the soils are class 1 or prime for rice. Still on-going is the study on given the erosion scenario (cm./per ten years), what would be the changes, if there be on the soil productivity ratin
Figure 10. Soil productivity rating map of the watershed.
