Not sure how to calculate waves on enclosed bodies of water.

If there was a long and narrow lake, say 30 km long and 5 km wide, but shallow, let’s say no more than 10m deep – what would be the worst size waves you would expect to encounter on this lake if you were designing a houseboat?
I assume the worst case scenario would be a strong wind blowing right down the length of it.
What if it were deeper, say 100m deep, would that effect the surface waves?

Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

party_pants said:

Not sure how to calculate waves on enclosed bodies of water.

If there was a long and narrow lake, say 30 km long and 5 km wide, but shallow, let’s say no more than 10m deep – what would be the worst size waves you would expect to encounter on this lake if you were designing a houseboat?
I assume the worst case scenario would be a strong wind blowing right down the length of it.
What if it were deeper, say 100m deep, would that effect the surface waves?

Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

you need to factor in the loch monster ratio

• Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

Probably been some wind tunnel work done on it…

Arts said:

party_pants said:

Not sure how to calculate waves on enclosed bodies of water.

If there was a long and narrow lake, say 30 km long and 5 km wide, but shallow, let’s say no more than 10m deep – what would be the worst size waves you would expect to encounter on this lake if you were designing a houseboat?
I assume the worst case scenario would be a strong wind blowing right down the length of it.
What if it were deeper, say 100m deep, would that effect the surface waves?

Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

you need to factor in the loch monster ratio

let’s say for the sake of argument I’m going to dig this lake from scratch and control what fish and aquatic animals I stock in it.

• let’s say for the sake of argument I’m going to dig this lake from scratch and control what fish and aquatic animals I stock in it.

party_pants said:

Arts said:

party_pants said:

Not sure how to calculate waves on enclosed bodies of water.

If there was a long and narrow lake, say 30 km long and 5 km wide, but shallow, let’s say no more than 10m deep – what would be the worst size waves you would expect to encounter on this lake if you were designing a houseboat?
I assume the worst case scenario would be a strong wind blowing right down the length of it.
What if it were deeper, say 100m deep, would that effect the surface waves?

Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

you need to factor in the loch monster ratio

let’s say for the sake of argument I’m going to dig this lake from scratch and control what fish and aquatic animals I stock in it.

seems shortsighted but ok.. I’ll leave you to your numbers and formulas…

Actually, this one works alright.

https://planetcalc.com/4442/

————

about 0.7 metres

If the lake waves at me, I’d reckon the drugs are very strong.

Arts said:

party_pants said:

Arts said:

you need to factor in the loch monster ratio

let’s say for the sake of argument I’m going to dig this lake from scratch and control what fish and aquatic animals I stock in it.

seems shortsighted but ok.. I’ll leave you to your numbers and formulas…

I don’t want anything eating my precious Tilapia

party_pants said:

Arts said:

party_pants said:

let’s say for the sake of argument I’m going to dig this lake from scratch and control what fish and aquatic animals I stock in it.

seems shortsighted but ok.. I’ll leave you to your numbers and formulas…

I don’t want anything eating my precious Tilapia

Mmmmm. Tilapia. Nice fish to eat.

:)

Michael V said:

party_pants said:

Arts said:

seems shortsighted but ok.. I’ll leave you to your numbers and formulas…

I don’t want anything eating my precious Tilapia

Mmmmm. Tilapia. Nice fish to eat.

:)

Horrible introduced fish.

party_pants said:

Not sure how to calculate waves on enclosed bodies of water.

If there was a long and narrow lake, say 30 km long and 5 km wide, but shallow, let’s say no more than 10m deep – what would be the worst size waves you would expect to encounter on this lake if you were designing a houseboat?
I assume the worst case scenario would be a strong wind blowing right down the length of it.
What if it were deeper, say 100m deep, would that effect the surface waves?

Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

I’ve done this, seriously, for CSIRO. I did it for waves in the Persian Gulf and applied it also to Australian conditions, such as Spencer Gulf and Port Phillip. I needed to calculate how much sea spray there would be to blow salt across the land, but the same would apply for lakes.

The first part is what is known as “fetch”, the length over which the wind blows, in this case 30 km. Then there are fetch-height relationships.

Here is an online calculator. https://woodshole.er.usgs.gov/project-pages/coastal_model/Tools/fetch_limited.html You only need to input the windspeed, fetch and water depth in order to calculate the wave height and wave period.

So, what wind speed? Obviously not tornado or hurricane force winds, unless your lake really is in a cyclone zone. So 40 m/s is too extreme. Perhaps you want the expected peak wind speed over a period of 10 years (mean speed not three second gust speed), on the grounds that that wind is unlikely to be blowing directly down the length of the lake. In my work, I’d do that by taking Met bureau data for the nearest met station, and use the highest recorded wind speed in the past 10 years. But that’s too messy for you.

I’ll think about what wind speed. Rev Dodgson could help you out here, too.

I’ve grown to hate the Beaufort Scale, but here it might be some help. The top wind speed for a Force 8 “fresh gale” is 46 mph, 20.5 m/s. You could use 20 m/s as your design wind speed for lake waves, or 25 m/s if you want to be on the safe side.

So plugging 25 m/s, 30 km and 10 m deep into the online calculator.

Significant wave height 2.4 metres with a wave period of 5.5 seconds – that’s impressive.

Let’s try 20 m/s, 30 km and 5 m deep.

Significant wave height 1.4 metres and wave period of 4.6 seconds – that’s still impressive. I didn’t expect a height that large.

Nice one mollwolfumble

mollwollfumble said:

party_pants said:

Not sure how to calculate waves on enclosed bodies of water.

If there was a long and narrow lake, say 30 km long and 5 km wide, but shallow, let’s say no more than 10m deep – what would be the worst size waves you would expect to encounter on this lake if you were designing a houseboat?
I assume the worst case scenario would be a strong wind blowing right down the length of it.
What if it were deeper, say 100m deep, would that effect the surface waves?

Any idea how to calculate this, so I can make up a spreadsheet and play with numbers?

I’ve done this, seriously, for CSIRO. I did it for waves in the Persian Gulf and applied it also to Australian conditions, such as Spencer Gulf and Port Phillip. I needed to calculate how much sea spray there would be to blow salt across the land, but the same would apply for lakes.

The first part is what is known as “fetch”, the length over which the wind blows, in this case 30 km. Then there are fetch-height relationships.

Here is an online calculator. https://woodshole.er.usgs.gov/project-pages/coastal_model/Tools/fetch_limited.html You only need to input the windspeed, fetch and water depth in order to calculate the wave height and wave period.

So, what wind speed? Obviously not tornado or hurricane force winds, unless your lake really is in a cyclone zone. So 40 m/s is too extreme. Perhaps you want the expected peak wind speed over a period of 10 years (mean speed not three second gust speed), on the grounds that that wind is unlikely to be blowing directly down the length of the lake. In my work, I’d do that by taking Met bureau data for the nearest met station, and use the highest recorded wind speed in the past 10 years. But that’s too messy for you.

I’ll think about what wind speed. Rev Dodgson could help you out here, too.

I’ve grown to hate the Beaufort Scale, but here it might be some help. The top wind speed for a Force 8 “fresh gale” is 46 mph, 20.5 m/s. You could use 20 m/s as your design wind speed for lake waves, or 25 m/s if you want to be on the safe side.

So plugging 25 m/s, 30 km and 10 m deep into the online calculator.

Significant wave height 2.4 metres with a wave period of 5.5 seconds – that’s impressive.

Let’s try 20 m/s, 30 km and 5 m deep.

Significant wave height 1.4 metres and wave period of 4.6 seconds – that’s still impressive. I didn’t expect a height that large.

Thanks, I have saved that calculator page.