Sensitivity analysis of relationships between hydrograph components and landscapes metrics extracted from digital elevation models with different spatial resolutions

Evaluation of sensitivity of hydrograph components and landscape metrics extracted from various spatial resolutions reveals relationships between landscape metrics and outflow properties with the lowest error. In the present study, 14 Digital Elevation Models (DEMs) with different resolutions derived from a vector and raster-radar source were analyzed to evaluate sensitivity of relationships between simulated hydrograph components and landscape metrics using multiple regression methods in the Galazchai Watershed, West Azerbaijan Province, Iran. To this end, DEM, slope, flow length and direction and time of concentration were developed in the vector and raster scales of 1:25000 and Advanced Land Observing Satellite-1 (ALOS) with different resolutions using ArcGIS 10.5 and ArcHydro software. Accordingly, 588 Direct Runoff Hydrographs (DRHs) were produced and clustered using Clark's Instantaneous Unit Hydrograph (IUH) model. The results showed that the best regression fits for flood volume and peak discharge were determined with Number of Disjunct Core Areas (NDCA) and Patch Density (PD) landscape metrics. Furthermore, the best regression fitted for time to peak and base time were observed with Core Area (CA) and Normalized Landscape Shape Index (NLSI) landscape metrics. In addition, the sensitivity analysis shows that the most sensitive spatial resolutions in modeling relationship between flood volume and peak discharge were determined at 5, 10, 20, and 30 m. The results revealed that hydrograph components in association with landscape metrics had high sensitivity to spatial resolutions, while the relationships between hydrological components and landscape metrics without considering the optimal spatial resolutions resulted in unacceptable results.</p

Accuracy of sedimentgraph modeling from topography map scale and DEM mesh size

The evaluation of scale effects on modeling performance of sedimentgraphs as the ultimate outputs of the hydrological simulation is vital for adaptive watershed management. The present study therefore analyzed effectability of simulated sedimentgraphs components in association with different topographic maps with various vector scales. The whole procedure was materialized to select the critical scale and cell size for the Galazchai Watershed, Iran. To this end, the stormwise sedimentgraphs were modeled for 23 recorded events using the Clark's Instantaneous Unit Hydrograph (IUH) model stemmed for developing Instantaneous Unit Sedimentgraphs (IUSGs) incorporated with dimensionless sediment concentration distribution (DSCD) based on the vector scales of 1:25000, 1:50000, 1:100000 and 1:250000 and cell sizes of 5, 10, 20 30, 50, 100 and 200 m. Some 644 direct sedimentgraphs (DSGs) were then evaluated based on Relative Errors (REs) for sediment volume, peak sediment, time to peak, base time and the Coefficient of Efficiency (CE). The results confirmed that REs for peak sediment, time to peak and CE were sensitive to cell size. The results further verified that the cell sizes of 5, 20, 30, 50 and 100 m were critical cell sizes in viewpoint of time to peak. In addition, the vector scales of 1:50000 with cell size of 50 m, and 1:100000 with cell sizes of 5 and 10 m were critical vector scales and cell sizes based on RMSE evaluation criterion. It is concluded from the current research that the accuracy of simulation of sedimentgraph was influenced by map scales and mesh sizes.</p