[Mike_Young]

On a course with 30,000 rounds would you say the average bunker would get 3000 shots?  less or more?

[Tom_Doak]

I'd guess the front right bunker [if it's medium to large sized] might see 5000 shots a year.  I'm thinking 4000 first attempts, and 1000 "others".     But I have never stood there a whole day to get enough data to make a good estimate.


The other bunkers would not get nearly that many.

[Mike_Young]

TD,I think you are about right...and I think the average bunker shot would explode 6 cubic inches of sand.  For a few years now I have heard dudes talk about 2 foot lips on some courses from displacement.  Might be a bunker here and there but I'm not sure the numbers make sense..the mower disperses the expelled sand each day and not sure I buy it...

[jeffwarne]

I've always doubted the theory.
In my experience I've had to beg to get people to finish the swing and splash sand all the way onto the green.


Many shots the ball is skulled with no sand.Because of this  many take tiny swings-fearing going over.
This results in small amounts of sand that doesnt go very far.
Practice bunkers? Sure


Sure.greens change but I'd guess wind blows more sand onto playing surfaces than sand wedges.

[Mark_Fine]

Mike,
Someone must have studied this before.  Soil probes don’t lie.  Have you or Tom or anyone here ever probed around some of the greenside bunkers you have built. It would be quite interesting to see what you find.  There is no question on the course we just worked on how much sand build up there was and how it varied from bunker to bunker.  It is fascinating actually but also not surprising.  Someone here more knowledgeable about this then I might chime in about The Road bunker (which we all know has been reconstructed over the years many times) and what they have found during reconstruction.


As far as top dressing goes; where do we all think the literally tons of sand goes that gets spread on to a green? 

[Garland Bayley]

...
Sure.greens change but I'd guess wind blows more sand onto playing surfaces than sand wedges.

When I joined my club, the 5th green had bunkers with bunker dams left and right both of about the same size. We are in a location that gets the Columbia Gorge winds. Said winds would blow sand towards the green from the left bunker, and away from the green from the right bunker. Perhaps 10 years ago the left bunker was rebuilt and the bunker dam removed. Now we have a lopsided green with little to no bunker dam on the left, and a bunker dam perhaps a foot above the green surface on the right. (As a member of the green committee, I have been advocating rebuilding the bunker on the right to regain symmetry.) If Jeff's theory is right, the left bunker should be building a dam from the wind and the right bunker dam should be diminishing. Me thinks it is not wind.

We also have a practice bunker that is at most 2 feet deep, but at 6 and a half feet, I can't see the ball land on the green because of the bunker dam that has built so high that I can't see over it. Another bunker dam I want removed.

Why aren't these things being addressed. Because, our board has been spending all our money on the club house. 

[Sean_A]

Wouldn't the depth of the greenside bunkers be a major factor? I rarely see much sand on greens from deeper bunkers. It's the ones with 2-3 feet lips close to greens where I see sand splash. I also see sand splash on fronts of greens when players hit out over the lower lip area rather than the steeper part of the bunker facing more toward the heart of the green. Don't build shallow bunkers, but especially near greens.

Ciao

[Jeff Schley]

Interesting question Mike.


I do have one golf tournament's worth of data for the four par 3 holes we have here at Rolling Hills GC in Dhahran, Saudi Arabia. Several years ago we got data of where everyone hit their tee shots on a plot diagram because a student was doing a project at school for his math class about averages. He got a google earth picture of each par 3 hole and he recruited 3 other classmates to sit by the green all day (2 day tournament) to put a dot where each person's tee shot landed. I'll provide a brief of each hole from the white tees and some photos from one guy's blog which did a pretty good job really, who played in the only open tournament we host each year. Don't know him but kudos for the good overview of playing from our back tees.  https://www.mjgolfguides.com/middle-east/saudi-arabia/rolling-hills-golf-course-dhahran/

Hole 4 - 212/193 - one large deep bunker in front of the green (4-7 feet deep) runs almost entire width of the green you need to carry and another bunker left of green 5 yards off the green. Wind typically right to left and many people going long to avoid bunkers.

Hole 8 - 148/135 - slightly uphill and you can't see the bunkers from the tee, but there are three bunkers surrounding almost the entire green. Large one short and left 5 feet deep. Medium deep one exactly right of green runs full depth of green. Devilish one directly behind the green runs back left to middle right and is 4-5 feet deep. Easier to give the openings 10 yard opening short right, 10 yards exactly left, maybe 5-6 yards long right.  Wind is slightly helping left to right prevailing, this is a very tough target as if it is a kidney shaped green with the left side of the green very thin with a bunker behind.


Hole 11 - 183/172 - uphill again with a big green only one medium sized bunker right of the green, but it is 3-4 feet deep. Wind is typically left to right here, so although not a large bunker with people's slices and the wind you can end up here.



Hole 14 - 189/174 - 3 total bunkers. Hole is downhill with two very deep 6-7 feet the entire left side, with one 4-5 foot deep bunker short right. Wind is helping right to left typically. Can run the ball up as the green is open here.

[Jeff Schley]

Can't put the stats in the above post easily so here they are for the tournament which was male/female monthly tourney we have for all members. Because of the number of players we do 2 shotgun starts (am/pm) on Friday and Saturday (our weekend). We don't totally fill up the course with 2 groups on each, so this particular tournament we had 321 people tee off over the two days. There is no breakdown of which of the three tee boxes were used (ladies, white, blue). I would estimate probably 40 ladies, 100 from the blue and the remaining 180 from the white. Distances are blue/white.


Hole 4, 212/193, handicap 14 - Very tough green to hit with a long iron or fairway wood.

• Large front bunker - 76 = 24%
• Left bunker - 31 = 10%
• Hit the green - 28 = 9%

Hole 8, 148/135, handicap 18 - kidney shaped, not much green left as it runs away into the back bunker last 3 feet, wind a factor to uphill hole hiding bunkers.

• Large short and left bunker - 101 = 31%
• Right bunker - 27 = 8%
• Back bunker - 43 = 13%
• Hit the green - 62 = 19%

Hole 11, 183/172, handicap 17 - large green with a pinnacle on back right.

• Right bunker - 22 = 7%
• Hit the green - 79 = 25%

Hole 14, 189/174, handicap 13 - downhill large green, but green runs away the entire back right so long is the miss here.

• 2 left bunkers (didn't separate) - 49 = 15%
• Short right bunker- 41 = 13%
• Hit the green - 45 = 14%

This just happens to be one course for one tournament in time. Wind, elevation, etc. all play a nuanced factor in the stats. However, just gives a glimpse of their use. We don't have a great club in terms of handicaps, the average handicap is 19.3 in our club last I looked.

• Hit into bunkers 390 out of 1,284 = 30%
• Hit the green 214 out of 1,284 = 17%

[Thomas Dai]

Sometimes a course will have a charity bunker.
On an ‘on trust’ basis players are meant to put a specified amount, say £1, into a jar every time they hit into a particular bunker, usually a greenside bunker.
Some players will put money into the jar, some players won’t, but I have wondered how much money £ is accumulated in a year.
The number of coins in the jar at year end ought, ought, if all players are complying, to be indicative of the number of bunker shots played. Likely though that you’ll have to add-on some maybe considerable factor for those not paying up!!
Atb

[jeffwarne]

Wouldn't the depth of the greenside bunkers be a major factor? I rarely see much sand on greens from deeper bunkers. It's the ones with 2-3 feet lips close to greens where I see sand splash. I also see sand splash on fronts of greens when players hit out over the lower lip area rather than the steeper part of the bunker facing more toward the heart of the green. Don't build shallow bunkers, but especially near greens.

Ciao

If the theory is true, maybe the bunkers were shallow to begin with

[Mike Nuzzo]

At Memorial I don't remember seeing any unusual amounts of build up, do you Tom?
They were 25 years old and see far more than 30,00 rounds a year - so more like the equivalent of 40 years at 30,000 rounds.
The only bunker with splash build up was the single little practice bunker that saw way more use than 5,000 shots per year, probably more like 100,000 per year - and it wasn't maintained as regularly as the course bunkers.
Cheers

[Mark_Fine]

Mike,
I noted in the other thread about sprinkler heads that are several inches below the surface?  How does this happen?  They don't sink.  I am sure you have done many soil probes.  This is not rocket science.  The sand build up comes from somewhere.  It doesn't just magically appear.  If you probe an old push up greens and find a foot of sand before you get to the topsoil, where did this come from?  I see this often.  Again, I work on a lot of courses that are not maintained at the highest standards (they don't have maintenance massive budgets) like you would find at many of the Top 100 courses so that surely has something to do with it. 


Regarding bunker floors, we have excavated bunkers where there is literally three feet of sand in the bottoms.  As most know, one of the popular ways "to fix" contaminated bunkers is to dump more fresh sand in them.  Of course this is only a bandaid and only works for so long but the end result is the floors of bunkers continue to raise up. 

[Tom_Doak]

Mike,
I noted in the other thread about sprinkler heads that are several inches below the surface?  How does this happen?  They don't sink.  I am sure you have done many soil probes.  This is not rocket science.  The sand build up comes from somewhere.  It doesn't just magically appear.  If you probe an old push up greens and find a foot of sand before you get to the topsoil, where did this come from?  I see this often.  Again, I work on a lot of courses that are not maintained at the highest standards (they don't have maintenance massive budgets) like you would find at many of the Top 100 courses so that surely has something to do with it. 
 

A lot of that is just the topdressing you were supposedly an expert about on the other thread about evolving green contours.

[Tom_Doak]

Wouldn't the depth of the greenside bunkers be a major factor? I rarely see much sand on greens from deeper bunkers. It's the ones with 2-3 feet lips close to greens where I see sand splash. I also see sand splash on fronts of greens when players hit out over the lower lip area rather than the steeper part of the bunker facing more toward the heart of the green. Don't build shallow bunkers, but especially near greens.

If the theory is true, maybe the bunkers were shallow to begin with

I have seen that very thing on a busy public course near me.  Most of the bunkers are shallow, but a few that are in front of the greens have a two-foot mound directly behind them, eating into the green.

[Tom_Doak]

At Memorial I don't remember seeing any unusual amounts of build up, do you Tom?
They were 25 years old and see far more than 30,00 rounds a year - so more like the equivalent of 40 years at 30,000 rounds.
The only bunker with splash build up was the single little practice bunker that saw way more use than 5,000 shots per year, probably more like 100,000 per year - and it wasn't maintained as regularly as the course bunkers.
Cheers

Mike:


That's true, I don't remember seeing much buildup there.  The old 2nd green had some, I think -- bunker right in front.


I have certainly seen buildup at other courses . . . Riviera, SFGC, Royal Melbourne, Pacific Dunes.  All of those except Riviera are pretty windy places, and their bunkers are pretty large, so some [or a lot] of it is probably wind erosion rather than actual bunker play.  And, certainly, if it's a breezy place, the sand from golf shots would be more likely to wind up on the lip of the bunker, too.

[Kalen Braley]

I'm inclined to agree with Jeff on this one.  Two factors as I see it for the vast majority of public play as I've observed over the years

1)  Bunkers aren't maintained nearly as often or as well.  Not uncommon to find damp, heavy, dense sand that doesn't move around very well, compared to the fluffy white stuff you see on TV.
2)  Most weekend warriors are not striking greenside shots properly most of the time, either too fat or thin.

Resulting in the vast majority of the sand remaining in the bunker, even on those with smaller 3-4 foot lips.

[Jeff_Brauer]

Took a slightly different tack on this.  Went back to Dr. Broadie's ball dispersion chart for D players, scaled it down from tee shots to a 160 yard approach.  The median dispersion for D players is about 7.5 degrees each way, total of 15. 


A typical green might be 60 feet wide (maybe 72 with an 8' wide shoulder for mowing turns) scales out to about 4.5 degrees each side of center., or about 60% of median dispersion for bogey players.  In fact, the USGA says  that same 24 yards wide should accommodate 66% of bogey golfers. 


But, I scaled off a few shot results from Broadie, and it seems as if about 23% of each side stays within 4.5 degrees AND goes far enough to reach the green, or perhaps 46% of total.  Of course, all of this assumes dispersion patterns on approach shots is about the same as tee shots, but I believe they tend to be slightly wider off the ground than off a tee.  Off the rest, based on some other stats I have seen, 23% are topped and come up short, and about  6% fly well wide of any standard sized bunker.  Depending on bunker placement, and assuming one front right and front left, we can presume almost half are bunker candidates, but then, probably only half of those would find any one bunker. 


That study traced 513 shots, and 48% of is about 246, and lets just say only 123 of those make a bunker.  123/513 is back to 23% overall.  IF all players were D players, that might make up 7192 shots.  However, D players make up about 16% of handicaps, and anecdotally, have fewer official handicaps among them, so they may make up only 33% of golfers, with C, B, and A players making up 66%.  Figuring each group is proportionally more accurate (which is logically and statistically true) then over 30,000 rounds, total shots in a bunker near any given green would reduce by a third to about 2375, or 8% of shots, which you can extend out or back. 


On a given day, 8% of 200 rounds might be 16 shots in the typical right front green side bunker? Seem about right?


Obviously, any bunker should be examined for position (i.e., short right is more likely to see shots) size, etc.

[Mark_Fine]

Tom,
I don't profess to be an expert on this.  I am just stating observations and experiences I have encountered.  And yes I know the sunken sprinkler heads come from top dressing.  Also you stated:


"I have seen that very thing on a busy public course near me.  Most of the bunkers are shallow, but a few that are in front of the greens have a two-foot mound directly behind them, eating into the green."

Does that mean you think that sand mound came from the bunker or was there to begin with?  Also, the mound eating into the green is part of what I am talking about.  Over time if not addressed, it will become more and more pronounced.

Jeff,
We definitely found far more buildup on front right bunkers.  The least build up was back left bunkers.  It was actually fascinating to study. 

Note to all:  I just texted our super at Lehigh CC just to get his two cents.  My question was, did he see sand buildup around his green side bunkers and on greens coming from the bunkers during the bunker renovation that he was involved in.  His answer was as follows:

"Yes that's very common.  When we redid the bunkers at Lehigh I had at least 2 feet of sand accumulation in areas especially the par 3s".

Lehigh is a pretty high end course so you can imagine what you will find on lesser maintained courses with much more play. 

[Tom_Doak]

That study traced 513 shots, and 48% of is about 246, and lets just say only 123 of those make a bunker.  123/513 is back to 23% overall.  IF all players were D players, that might make up 7192 shots.  However, D players make up about 16% of handicaps, and anecdotally, have fewer official handicaps among them, so they may make up only 33% of golfers, with C, B, and A players making up 66%.  Figuring each group is proportionally more accurate (which is logically and statistically true) then over 30,000 rounds, total shots in a bunker near any given green would reduce by a third to about 2375, or 8% of shots, which you can extend out or back. 

On a given day, 8% of 200 rounds might be 16 shots in the typical right front green side bunker? Seem about right?

I had thought about doing the math on it, but waited until you did it, instead!   


But did you do it right?  You had the D players doing it 23% of the time, but they're only 1/3 of the total rounds, so you reduced that to 8%.  But you didn't add anything back for the A, B, and C players who play the other 2/3 of the rounds.  If they get in the bunker half as often, but there are twice as many of them, then you are back up close to 5000 rounds.


I think your 8% overall number seems low.

[Tom_Doak]

Note to all:  I just texted our super at Lehigh CC just to get his two cents.  My question was, did he see sand buildup around his green side bunkers and on greens coming from the bunkers during the bunker renovation that he was involved in.  His answer was as follows:

"Yes that's very common.  When we redid the bunkers at Lehigh I had at least 2 feet of sand accumulation in areas especially the par 3s".

One of the questions not addressed is how long it's been since the bunkers or greens were redone.  If you are talking about five or ten years, the buildup is probably not that much.  If you're talking about a course that hasn't been redone in 50 years, it could easily be two feet in places.


P.S.  I meant that the little bunker I was talking about near home [Interlochen GC in Michigan] was almost certainly flat when it was built, just like all the rest.

[Mark_Fine]

Tom,
Good point about how old the bunkers are.  Many of the courses I work on the bunkers are OLD, some not purposely altered in a long time.  Again, someone must have studied this as there have been a zillion bunker projects done over the years.  I know I am not the only one doing soil probes and checking for original bunker/green shapes and depths, etc. 


Jeff,
Has the ASGCA ever studied this? 

[Jeff_Brauer]

Tom,


Doing math wrong is always a possibility with me, especially when I was going to kill the last ten minutes before a lunch meeting, and got going too fast.


Mark,


No, we haven't studied this. I recall Golf Digest having some charts about where approach shots miss.  I know a few members who have gone in the field to chart tee shot length and width (which correlate to Broadie pretty closely) and I have personally gone out to measure how much up slope is required for average players to hold a green (1.33% or more, but maybe Tom D can check my math on that one.)


At one point, ASGCA had some kind of intern program, funding interested college students to do some mundane research.  I will check on that, as to me, ball dispersion pattern studies seem like kind of an ASGCA-ish thing to do.

[Mark_Fine]

Jeff,
I would be interested in that and also in the impact of sand tossed from bunkers on changing bunker surrounds/greens.  Top dressing impact would also be of interest.  I can ask Forrest if he didn't see this thread.  This kind of information could be very helpful to clubs/courses doing various improvement projects. 

[Sean_A]

Wouldn't the depth of the greenside bunkers be a major factor? I rarely see much sand on greens from deeper bunkers. It's the ones with 2-3 feet lips close to greens where I see sand splash. I also see sand splash on fronts of greens when players hit out over the lower lip area rather than the steeper part of the bunker facing more toward the heart of the green. Don't build shallow bunkers, but especially near greens.

Ciao

If the theory is true, maybe the bunkers were shallow to begin with

Do you see sand on Raynor greens? 

Ciao

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