Category: Urban Systems

Soil Compression Index

Soil Compression Index

Soil Compression Index

09/07/25

“How can we measure the compressibility of fine-grained soils to effective stress?”

When soil is drained of water and air, the particles will close together and consolidate, increasing effective stress. The Soil Compressive Index measures the ratio of the change in void ratio to the change in effective vertical stress. The equation solid compression index = change in void ratio/log_10(final effective vertical stress/initial effective vertical stress), or C_c = delta_e/(log_10(sigma_2’/sigma_1’)), governs the solid compression index. 

Aquifer Storativity

Aquifer Storativity

Aquifer Storativity

09/05/25

“How can we quantify the volume of water an aquifer is likely to release when there’s a change in head pressure?”

Wells pull water up from aquifers through pressure head reduction. But every aquifer is different, and we need to quantify how much water a formation is likely to release per pressure head reduction. Luckily, we have a parameter called Aquifer Storativity that measures the amount of water released per area to a given change in pressure head. For confined aquifers, storativity is equal to the specific storage times the aquifer thickness.

Aquifer Transmissivity

Aquifer Transmissivity

Aquifer Transmissivity

09/04/25

“How can we quantify the transmissive capabilities of an aquifer system?”

When water is pumped out of an aquifer, the aquifer’s properties will determine how fast and how much water will come to the well pump. The rate at which an aquifer can horizontally transmit water is called Aquifer Transmissivity. Aquifer transmissivity is measured in area per time unit, proportional to the product of the aquifer’s hydraulic conductivity and saturated thickness.

Aquifer Drawdown

Aquifer Drawdown

Aquifer Drawdown

09/03/25

“What happens to an aquifer’s pressure head when a well is inserted?”

Inserting objects into an aquifer will change its properties. When a well is inserted, the groundwater’s hydraulic head is reduced. The closer a piece of groundwater is to the well, the more it is reduced. This decrease in pressure is known as Aquifer Drawdown. Aquifer drawdown is important for completing aquifer water production field tests.

Spillways

Spillways

Spillways

09/01/25

“How can we release water from a dam when it’s too full?”

Dams and reservoirs hold a certain amount of water. When there’s too much water, it can damage the dam and the surrounding area. So what if we were to design a mechanism that allows us to release a certain amount of water before overflow occurs? Well, this is the idea behind Spillways. Spillways come in all shapes and sizes and are a fundamental part of many water containment infrastructure systems.

Trellis Drainage Patterns

Trellis Drainage Patterns

Trellis Drainage Patterns

08/31/25

“How do grid-like rivers form?”

Drainage pattern shapes form based on the local geology. Sometimes, the surface might have alternating bands of resistant and non-resistant rock. When water flows over these surfaces, the non-resistant rock erodes more steadily and turns into a valley between the resistant rock bands. The main tributaries of these rivers will run through these valleys and form perpendicular streams down the edges of the ridges of the resistant layers. These Trellis Drainage Patterns are prone to flooding because the water flowing through the valleys can overflow during heavy rains. Bakudabakek/Wekwabegituk (also named “The Bay of Fundy” by the settler-colonial state of Canada) is an example of a trellis drainage pattern.

Image credit: i.pinimg.com

Parallel Drainage Patterns

Parallel Drainage Patterns

Parallel Drainage Patterns

08/26/25

“Why do some rivers flow down in parallel lines?”

Dendritic drainage patterns form when there are no major geological challenges to river flow. Something interesting is that when the slopes are constantly steep (greater than 5 degrees), the forces of gravity will force the different “branches” to become parallel to each other. These Parallel Drainage Patterns move in a consistent direction with consistent spacing from one another. Some rivers in the Lesser Himalayas exhibit parallel drainage patterns.

Image credit: https://i0.wp.com/

Dendritic Drainage Patterns

Dendritic Drainage Patterns

Dendritic Drainage Patterns

08/25/25

“What is the most common type of drainage pattern?”

Close your eyes and visualize a drainage pattern. You’ll probably think of a river with a power center, with smaller branches periodically coming out, and even smaller branches coming out of those, analogous to a tree trunk with branches and leaves on those branches. Have you ever wondered what exactly makes it this way? Well, this happens because as water flows downhill due to gravity, it will seek the lowest path downward. If the geology is fairly uniform and there are no major faults, the main flow direction will form the main river branch, while other headwaters will naturally flow into it. This will form the Dendritic Drainage Patterns that we all know. Dendritic drainage patterns are the most common form of drainage patterns in the world.

Image credit: https://i.pinimg.com/

Cloudburst Hubs

Cloudburst Hubs

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/