Publications

2025

1. Assessing the Impact of Radar-Rainfall Uncertainty on Streamflow

   Bongchul Seo Nicolás Velásquez

   Journal of Hydrometeorology, 2025

2024

1. Effect of streamflow measurement error on flood frequency estimation

   Nicolás Velásquez, and Witold F. Krajewski

   Stochastic Environmental Research and Risk Assessment, 2024

2023

1. Snow-detonated floods: Assessment of the US midwest march 2019 event

   Nicolás Velásquez, Felipe Quintero, Sinan Rasiya Koya, and 2 more authors

   Journal of Hydrology: Regional Studies, 2023
2. Testing the Connection Between Hillslope Scale Runoff Fluctuations and Streamflow Hydrographs at the Outlet of Large River Basins

   Ricardo Mantilla, Morgan Fonley, and Nicolas Velasquez

   Hydrology and Earth System Sciences Discussions, 2023
3. Ensemble Kalman Inversion for upstream parameter estimation and indirect streamflow correction: A simulation study

   Andrew Pensoneault, Witold F Krajewski, Nicolás Velásquez, and 2 more authors

   Advances in water resources, 2023

2022

1. Assessment of Deep Convective Systems in the Colombian Andean Region

   Nicolás Velásquez

   Hydrology, 2022
2. Sequential surface and subsurface flow modeling in a tropical aquifer under different rainfall scenarios

   Mariana Jimenez, Nicolás Velásquez, Jhon Esteban Jimenez, and 8 more authors

   Environmental Modelling & Software, 2022
3. Assessment of Deep Convective Systems in the Colombian Andean Region

   Nicolás Velásquez

   Hydrology, 2022

2021

1. Improving Hillslope Link Model Performance from Non-Linear Representation of Natural and Artificially Drained Subsurface Flows

   Nicolás Velásquez, Ricardo Mantilla, Witold Krajewski, and 2 more authors

   Hydrology, 2021
2. Development and Evaluation of an ODE representation of 3D subsurface tile drainage flow using the HLM flood forecasting system

   M. R. Fonley, K Qiu, N. Velásquez, and 2 more authors

   Water Resources Research, 2021

   Abs

   We developed a new ordinary differential equation (ODE) to represent subsurface flows from a hillslope with artificial subsurface drainage (tiling) into an adjacent channel. Our ODE is based on a derived storage-discharge relationship from high-resolutions HYDRUS3D simulations that solve 3D partial differential Richards’ equations for a hillslope (plot scale) with internal drainage surfaces, variable soil depth, hydraulic conductivity, and varying slope in the direction of flow. The ODE does not capture the hysteresis in the storage-drainage relation that can only be captured using partial differential equations (PDEs), however the simplification does not have major impacts on the modeled flows. The nondimensional representation of the equation is consistent with, and provides an explanation for, the empirical equation used in classical hydrological models such as the ARNO (Arno River) and Variable Infiltration Capacity (VIC) model to simulate subsurface flows, which removes the need for parameter calibration. Our equation captures the features not captured by other ODE simplifications such as DRAINMOD. The ODE can be coupled to the Hillslope Link Model (HLM) flood forecasting system allowing real-time regional simulation of streamflow fluctuations and floods over large domains. We show that (i) the new equation improves the capability to model watershed scale hydrograph recessions and to better capture the timing above flood thresholds for multiple spatial scales from 0.1 to 18,000 km2; (ii)using realistic values of slope combined with typical values of tile separation and soil depth provides good predictive power at gauged basin outlets; and (iii) parameters can be derived for particular situations using the 3D PDE framework.

2020

1. Limits of predictability of a global self-similar routing model in a local self-similar environment

   Nicolas Velasquez, and Ricardo Mantilla

   Atmosphere, 2020

   Abs

   Regional Distributed Hydrological models are being adopted around the world for prediction of streamflow fluctuations and floods. However, the details of the hydraulic geometry of the channels in the river network (cross sectional geometry, slope, drag coefficients, etc.) are not always known, which imposes the need for simplifications based on scaling laws and their prescription. We use a distributed hydrological model forced with radar-derived rainfall fields to test the effect of spatial variations in the scaling parameters of Hydraulic Geometric (HG) relationships used to simplify routing equations. For our experimental setup, we create a virtual watershed that obeys local self-similarity laws for HG and attempt to predict the resulting hydrographs using a global self-similar HG parameterization. We find that the errors in the peak flow value and timing are consistent with the errors that are observed when trying to replicate actual observation of streamflow. Our results provide evidence that local self-similarity can be a more appropriate simplification of HG scaling laws than global self-similarity.

2. Reconstructing the 2015 Salgar flash flood using radar retrievals and a conceptual modeling framework in an ungauged basin

   Nicolás Velásquez, Carlos D. Hoyos, Jaime I. Vélez, and 1 more author

   Hydrology and Earth System Sciences, 2020

   Abs

   On 18 May 2015, a severe rainfall event triggered a flash flood in the municipality of Salgar, located in the northwestern Colombian Andes. This work aims to reconstruct the main hydrological features of the flash flood to better understand the processes modulating the occurrence of the event. Radar quantitative precipitation estimates (QPEs), satellite information, and post-event field visits are used to reconstruct the Salgar flash flood, in an ungauged basin, addressing the relationship among rainfall spatiotemporal structure, soil moisture, and runoff generation during successive rainfall events by using a conceptual modeling framework including landslide and hydraulic submodels. The hydrological model includes virtual tracers to explore the role of runoff and subsurface flow and the relative importance of convective and stratiform precipitation in flash flood generation. Despite potential shortcomings due to the lack of data, the modeling results allow an assessment of the impact of the interactions between runoff, subsurface flow, and convective-stratiform rainfall on the short-term hydrological mechanisms leading to the flash flood event. The overall methodology reproduces the magnitude and timing of the La Liboriana flash flood peak discharge considerably well, as well as the areas of landslide occurrence and flood spots, with limitations due to the spatial resolution of the available digital elevation model. Simulation results indicate that the flash flood and regional landslide features were strongly influenced by the antecedent rainfall, which was associated with a northeasterly stratiform event. The latter recharged the gravitational and capillary storages within the model, moistening the entire basin before the occurrence of the flash flood event and impacting the subsurface-runoff partitioning during the flash flood event. Evidence suggests that the spatial structure of the rainfall is at least as important as the geomorphological features of the basin in regulating the occurrence of flash flood events.

2019

1. Meteorological conditions leading to the 2015 Salgar flash flood: lessons for vulnerable regions in tropical complex terrain

   Carlos D Hoyos, Lina I Ceballos, Jhayron S Pérez-Carrasquilla, and 8 more authors

   Natural Hazards and Earth System Sciences, 2019

2013

1. Evaluación espacial multicriterio para la localización de picocentrales en Antioquia

   Nicolas Velasquez Giron Laura Garc\’\ia Vélez Engelberth Soto Estrada Martha Isabel Posada

   Revista CIDET, 2013

2011

1. Rainfall Distribution Based on a Delaunay Triangulation Method

   Nicolas Velasquez, Veronica Botero, and Jaime Ignacio Velez

   Transactions on Computational Science XIV, 2011