Cloudburst Hubs

08/24/25

“How is New York City using modern planning and engineering techniques to adapt to cloudburst flooding events?”

Cloudbursts release a voluminous amount of rain in a short amount of time, which can cause widespread damage to people and infrastructure. New York City is taking an innovative approach to protecting against these events through its Cloudburst Hubs. Cloudburst hubs are hydraulically connected areas in NYC that are vulnerable to deep flooding and can also include infiltration, storage, and conveyance to reduce the flood depths of hotspots, connect onsite with right-of-way strategies, including diverting street runoff, and use a combination of green-grey strategies to mitigate against floods. These cloudburst hubs can help city residents adapt to the new climate paradigm. 

Image credit: https://www.nyc.gov/

How to Calculate Power for Hydraulic Pumps

08/20/25

“How do we calculate power for hydraulic pumps?”

Hydraulic pumps are a pillar of modern water infrastructure. Through their mechanisms, they can create a pressure differential to match the needs of people. But pumps need power to operate, and we may need to calculate the power to accomplish what our goals. To do this, we can go to the simple physics equation (1) work = force * distance (W = F * h). Going further, we may notice that if we’re lifting a fluid, the force will be equal to (2) the fluid’s mass * gravity (m_fluid * g), and (3) mass of fluid = density of fluid * volume of fluid (m_fluid = rho_fluid * V_fluid).  This is related to power through the equation (4) P = dW/dt, where Power is P. We can plug in equation (1) to (4) to make (5) P = d(F * h)/dt. → dF/dt*ht. If we substitute in equation (3), we get (6)  P =  (d(rho_fluid * V_fluid*g)/dt*h), and by (7) fluid flow = change in fluid over time (Q = dV_fluid/dt), we can substitute for (8) P = rho_fluid * g * h * dV_fluid/dt → P = rho_fluid * g * h * Q. And by remembering that (9) specific weight = density of fluid * gravity (Gamma_fluid = rho_fluid * g), we can finalize with (10) P = Gamma_fluid * Q * h. This is How to Calculate Power for Hydraulic Pumps. The pump’s efficiency will also affect this value.

Manning’s Roughness Coefficient

08/19/25

“How can we measure the resistance to fluid flow in channels and floodplains?”

Fluids flow through open channels in conduits and floodplains. The structures supporting fluid flow provide resistance to movement. The structure’s base surface roughness, stage and discharge, obstructions, geometric irregularities and alignment, vegetation, and debris contribute to fluid resistance. These are quantitatively summarized by Manning’s Roughness Coefficient, a variable vital for channel flow calculations. Manning’s roughness coefficients for various materials are found in engineering reference manuals.

Ponding

08/17/25

“What happens when water has no place to drain?”

Water will collect over land when there are insufficient infiltration capabilities. If this water has no place to drain, it will coalesce into a sizable puddle. This Ponding process can produce small bodies of water that can carry pollutants, become mosquito nesting grounds, and even damage building structures if it collects on a small roof.

Potential Maximum Retention

08/16/25

“How can we quantify the maximum amount of water a watershed can hold before runoff?”

Watershed geologies can hold a certain amount of moisture before runoff occurs. We can measure this through the Potential Maximum Retention, a hydrological quantity that represents the maximum amount of water a watershed can absorb before starting runoff.

 Initial Abstraction (Hydrology)

08/15/25

“How can we quantify the initial rainfall losses before runoff begins?”

Rainfall will lead to water hitting the ground. Before anything happens, some of the rainfall will get intercepted by vegetation or infiltrate into the ground and get lost from the system. Hydrologists represent this value as the Initial Abstraction. Initial abstraction is an important quantity in hydroshed and stormwater studies.