According to the local authorities
and the landowners, channel geometries were and still are generally homogeneous over each property, being related to the trenchers used to build the channels. During the considered time span, for our study area, the trenchers measurements did not change, therefore we assumed that for the year 1954 and 1981 we could apply the same width for each sub-area as the one of the year 2006 (see next section). In addition to the agrarian RG7420 ic50 network storage capacity, for the year 1981 we considered also the urban drainage system and we added the culvert storage capacity. For the year 1954, this information was not available. For the year 2006, we applied the Cazorzi et al. (2013) methodology. This approach allows to evaluate semi-automatically the network drainage density (km/km2) and
storage capacity (m3/ha). Having a lidar DTM (in our study case a lidar DTM available publicly and already applied in other scientific studies i.e. Sofia et al., 2014a and Sofia et al., 2014b), it is possible to derive a morphological Everolimus index called Relative Elevation Attribute (REA). This parameter represents local, small-scale elevation differences after removing the large-scale landscape forms from the data, and it is calculated by subtracting the original DTM from a smoothed DTM (Cazorzi et al., 2013). Through a thresholding approach based on the standard deviation of REA, the method allows to automatically extract a Boolean map of the drainage network. Starting
from this Boolean map, it is possible to characterize automatically for each extracted channel fragment its average width and length, and by applying some user-defined parameters it is possible to derive its average storage capacity. The measures of each channel fragment are then aggregated over each subarea, obtaining the drainage density and the storage capacity. The storage capacity strictly depends on the channel size. Agricultural drainage networks in the north east of Italy have a highly regular shape, connected to the digging techniques used to create the ditches. Based on this principle, the procedure by Cazorzi et al. (2013) requires the user to characterize Phosphoglycerate kinase the channel shape by defining average measures of cross-section areas per width ranges. This classification is used as a conditional statement to calculate the storage capacity: if the extracted width is within one of the considered ranges, the procedure consider the user-defined cross sectional area for that range, and multiplies it for the extracted channel fragment length, obtaining an average storage capacity per extracted network fragment. To define a number of representative cross-sectional areas per specific width ranges, we conducted a field survey campaign, using DGPS, measuring the network widths and cross-sectional areas, and we found that (1) our data well overlap with the ones considered by Cazorzi et al. (2013) (Fig.
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