Derivation and Application of Idealized Flow Conditions in River Network Simulation

Abstract:

Stream flow information is essential for many applications across broad range of scales, e.g. global water balances, engineering design, flood forecasting, environmental management, etc. Quantitative assessment of flow dynamics of natural streams, requires detailed knowledge of all the geometrical and geophysical variables (e.g. bed-slope, bed roughness, etc.) along river reaches. Simplifying the river bed geometries could reduce both the computational burden implementing flow simulations and challenges in assembling the required data, especially for large domains. Average flow conditions expressed as empirical “at-a-station” hydraulic geometry relationships between key channel components, (i.e. water depth, top-width, flow velocity, flow area against discharge) have been studied since 60's. Recent works demonstrated that power-function as idealized riverbed geometry whose parameters are correlated to those of exponential relationship between mean water depth and top-width, are consistent with empirical "at-a-station" relations.

US Geological Surveys' National Water Information System web-interface provides huge amount of river discharge and corresponding stage height data from several thousands of streamflow monitoring stations over United States accompanied by river survey summaries providing additional flow informations (width, mean velocity, cross-sectional area). We conducted a series of analyses to indentify consistent data daily monitoring and corresponding survey records that are suitable to refine our current understanding of how the "at-a-station" properties of river channels relate to channel forming characteristics (e.g. riverbed slope, flow regime, geology, etc.). The resulting ~1,200 actively operating USGS stations with over ~225,000 corresponding survery records (almost 200 survey per gauge on average) is the largest river survey database ever studied in the past.

Our presentation will show our process assembling our river monitoring and survey data base and we will present our first results translating "at-a-station" relations into he hydraulic geometry of river channels based on idealized power-law riverbed geometries. We also will also present a series of application (e.g. improved flow rounting, simplyfied river surveying).