Remote Sensing in the Sonoma Baylands

• The following aerial photographs in digital format were used in the project :

  26 April 1993, CIR 790 x 554, 413k	April 26, 1993: This is a color-infrared (CIR) photograph taken in the spring BEFORE any restoration work was started and corresponds to a pre-restoration image. Keep in mind that in CIR images vegetation is red and water is generally dark to light blue, depending on the amount of suspended sediments and chlorophyll in the water. The scale of the original photograph was approximately 1:63K.
  19 October 1994, CIR 790 x 554, 426k	October 19, 1994: This is also a CIR photograph taken in the fall when vegetation is dormant. Only the pilot unit has water, and suspended sediment patterns can be seen fanning out from the small channel connecting it to the Bay waters. Because of the lack of water in the main unit at this time, the physical design and layout can be seen. The scale of the original photograph was approximately 1:65K, which we found to not have sufficient spatial resolution for detecting and monitoring erosion along the small channels connecting the restoration site with the Bay.
  8 October 1996, CIR 790 x 554, 380k	October 8, 1996: This is also a CIR photograph taken in the fall when the vegetation is dormant. Both the pilot and main units are now filled with water. In this photograph the information in the water is minimal. Some of the general low-to-high suspended sediment patterns in the main unit can be seen, but do not show up very well. The scale of the original photograph was approximately 1:68K, so again the resolution is not acceptable for detecting and monitoring erosional changes along the small narrow channels.
  3 May 1997, CIR 790 x 554, 386k	May 3, 1997: This CIR photograph was the most recent one available and was taken in the spring when vegetation was no longer dormant, but still not in full bloom. Because of the high amount of sun glint, there is not much information in the water; therefore, these data were not very useful for extracting suspended sediment information. Again, because of the scale (approximately 1:66K) the photograph was not useful for detecting erosional changes in the small channels.
  27 August 1996, CIR 790 x 554, 333k 27 August 1996, NC 790 x 554, 390k	August 27, 1996: There was both a CIR and Natural Color (NC) photograph for this date from a NOAA Bay-wide survey. The scale of the photographs was approximately 1:24k, which made them more applicable for mapping channel erosion, but it turned out that the resolution was still not sufficient for detecting changes in the small channels. In these photographs, especially in the natural color, we can clearly see various patterns in the water. Some of these patterns are related to the amount of suspended sediments in the water, but may also be related to the amount of chlorophyll and algae in the water. At this stage we are not certain if penetration of the water to the bottom occurred, so the colors seen may or may not have been affected by the bottom reflectance (we feel that little, if any, penetration to the bottom was made with the CIR photo, which also contains suspended sediment information). From this image it appears that parts of the main unit have more sediments going in to them than others. In the pilot unit a sediment fan can be seen at the entrance into the unit. The color of the water in the pilot unit is closer to the color seen in the Bay and Petaluma River. This, along with the drainage/channel information that can be seen in the CIR image, indicates that perhaps at the time this photograph was collected that there was better interaction between the bay/river waters and the pilot unit than with the main unit. Since these are archival photographs, no ground truth information was collected during the overflights; therefore, photo interpretation and analysis was done using previously acquired expertise about the affect of low to high suspended sediments on the colors seen in multispectral photographs and images.
  27 August 1996, Color-coded Suspended Sediment Map 790 x 554, 41k	Color-coded Suspended Sediment Map: This image product was generated using the natural color photograph and processing the data so that general color/brightness patterns that could be related to suspended sediment concentrations would be enhanced. The color bar at the bottom of the image shows a related scale of suspended sediment concentrations mapped from the digital data. The concentrations are shown only in a relative sense of the lack of actual field data during the time of overflight and the collection of the photograph. The concentrations range from low to high using the colors light green to brown and red, respectively. Notice that the higher concentrations are in the pilot unit, with the higher concentrations in both the piolot and main units being close to the entrance of the channel waters.

After analyzing the various digital removely sensed images, one of our conclusions was that higher resolution photos are needed to monitor changes in the small channels caused by erosion of the bay waters interacting with the restoration site. We recommend that aerial photographs with a scale of approximately 1:10K be used to detect changes within small drainage channels like those at the Sonoma Baylands restoration site (2 to 3 meters wide). Even with a spatial resolution of one foot, the number of pixels across such small channels would be only about 6 to 9 pixels. This is generally not enough to see the level of erosional changes that are of interest because the changes will be in the order of less than one or two feet between photograph dates.

• Digital Satellite Images
• Ground-Based Digital Camera Photographs

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