Limpasan Permukaan (Run Off) dan Faktor yang mempengaruhinya

Summary

This video discusses surface runoff, also known as runoff, which refers to rainwater that flows over the ground surface due to gravity, infiltrates, or becomes part of groundwater. Key factors influencing runoff include climate, topography, vegetation, geology, and human activities. The script explores methods for calculating runoff using rational methods, coefficients, and hydrological models. It also addresses how different landscape features, precipitation patterns, and human interventions impact runoff flow rates. The concept of runoff distribution over time and space is explained, emphasizing its importance in hydrology and flood management.

Takeaways

• 😀 Surface runoff (or runoff) is water that flows over the land's surface, due to rainfall or precipitation, and is influenced by gravity. It consists of both surface flow and groundwater flow that eventually reaches rivers.
• 😀 Runoff is an important component of the water cycle and can be calculated using rational methods and various formulas that include rainfall intensity, drainage area, and specific coefficients.
• 😀 The runoff coefficient (C) indicates the proportion of rainfall that becomes runoff, helping to estimate the amount of water that will flow through a drainage system.
• 😀 The runoff calculation can also include parameters like topography, soil type, and vegetation coverage to estimate runoff accurately using models such as the Haze model or the USBFS method.
• 😀 Topography plays a crucial role in runoff speed; steep areas contribute to quicker runoff, while flatter regions result in slower runoff.
• 😀 Runoff distribution can vary based on the characteristics of the watershed (catchment area) and its landforms, as well as precipitation distribution over time.
• 😀 Meteorological factors like rainfall intensity and duration affect the spread and amount of runoff, with higher precipitation leading to increased runoff.
• 😀 Soil properties, such as permeability and the type of bedrock (sedimentary or igneous), determine the rate at which water infiltrates the ground and, consequently, the volume of runoff.
• 😀 Vegetation can help reduce runoff by absorbing and slowing down water, thereby minimizing the impact of heavy rainfall.
• 😀 Human activities, such as urbanization or land use changes (e.g., converting forests into built-up areas), can significantly increase runoff, as impermeable surfaces prevent water infiltration into the ground.

Q & A

What is surface runoff or 'ranof'?

Surface runoff, or 'ranof', refers to the portion of rainfall that flows over the surface of the land, moving due to the force of gravity. It includes water that does not infiltrate into the soil or evaporate, and it can flow on the surface or sub-surface, ultimately reaching rivers or groundwater.

What are the key components of runoff?

The key components of runoff include surface flow, sub-surface flow, and groundwater flow. These components refer to water flowing on the land's surface, beneath the surface, and in the underground water table, respectively.

How is runoff calculated using the rational method?

Runoff is calculated using the rational method by estimating rainfall intensity, land area, and a runoff coefficient, which indicates how much of the rainfall becomes runoff. The formula incorporates these factors to estimate the runoff volume.

What factors affect the runoff coefficient?

The runoff coefficient is influenced by several factors, such as topography, soil type, land use, and vegetation. For example, steep slopes may cause faster runoff, while porous soils can absorb more water, reducing runoff.

How does the topography of a watershed affect runoff?

Topography influences runoff by determining the speed at which water flows across the land. Steeper slopes lead to faster runoff, while flatter areas result in slower runoff. The shape of the land also affects how quickly water can move to the river or other drainage outlets.

What role does vegetation play in runoff?

Vegetation helps reduce runoff by intercepting rain and slowing down the movement of water. Plants absorb and store some water, preventing all of it from becoming runoff. Areas with dense vegetation typically experience lower runoff compared to urbanized or barren land.

How do land use changes affect surface runoff?

Changes in land use, such as urbanization or deforestation, can increase surface runoff. Urbanization leads to more impervious surfaces like concrete, which prevent water from infiltrating into the ground, thus increasing the amount of runoff. Deforestation can reduce the ability of the land to absorb rainwater.

What is the impact of rainfall direction on runoff?

The direction of rainfall movement affects how quickly runoff occurs. Rain moving from upstream to downstream results in faster runoff, while rain moving in the opposite direction (from downstream to upstream) may delay the flow, making the runoff slower and affecting its peak.

How does soil type influence runoff?

Soil type plays a critical role in determining runoff. Soils with high permeability, such as sandy soils, allow water to infiltrate, reducing runoff. In contrast, impermeable soils, like clay, restrict water infiltration, leading to higher runoff.

What are the effects of human activities on runoff?

Human activities, such as construction, deforestation, and land development, can significantly affect runoff. Urbanization increases impervious surfaces, leading to more runoff. Additionally, land-use changes like draining wetlands or converting forests into agricultural land can alter the natural water cycle, increasing flood risks.